,illu/ration3 ,satellite ,communications ,physics ,satellite ,communications ,physics ,,by ,,memb]s ,,( ,,! ,,/aff ,,( ,,bell ,,telephone ,,laboratories ,,editor3 ,,ronald ,m4 ,,fo/]1 ,jr4 ,h[ sci5ti/s & eng9e]s use basic physical pr9ciples to solve "s ( ! problems 9 communicat+ by means ( man-made satellites #aifc ,bell ,telephone ,laboratories1 ,incorporat$ ,all rights res]v$4 ,p]mission to reproduce any mat]ial conta9$ 9 ?is book mu/ be obta9$1 9 writ+1 f ! publi%]4 ,libr>y ( ,congress ,catalog ,c>d ,numb] #fc-baffg ,pr9t$ 9 ,u4,s4,a4 ,=eword ,john ,r4 ,pi]ce ,executive ,director1 ,rese>*1 ,communications ,pr9ciples & ,communications ,sy/ems ,bell ,telephone ,laboratories ,:5 ,i fir/ talk$ ab\t ! possibilities & advantages ( communications satellites to ! ,pr9ceton ,section ( ! ,in/itute ( ,radio ,eng9e]s on ! ev5+ ( ,octob] #ad1 #aied1 ,i 0 dilig5t 9 my analysis & en?usia/ic 9 my pres5tation b1 ,i mu/ confess1 a little skeptical z to :e!r or n any?+ w\ld come ( ! idea4 ,/ill1 o!rs & ,i at ,bell ,laboratories rema9$ int]e/$1 &1 aft] ! laun*+ ( ,sputnik ,i on ,novemb] #c1 #aieg1 & ( ,explor] ,i on ,janu>y #ca1 #aieh1 we work$ actively t[>d satellite communications exp]im5ts4 ,?is l$ to our "w ) ,e*o ,i 7laun*$ ,augu/ #ab1 #aifj7 & f9ally to ! laun*+ on ,july #aj1 #aifb1 ( ,tel/> ,i--t satellite :i* became1 9 ! words ( ,que5 ,elizabe?1 8! invisible focus ( a million eyes40 ,?is "w on communications satellites has be5 a gr& exploration & op5+ up ( a hi!rto d>k cont95t ( sci5ce & te*nology4 ,my c\rage\s fri5ds at ,bell ,laboratories enc\nt]$ !re9 surpris+ difficulties & p]plex+ problems :i* ,i _h nev] dream$ (1 & ^! intrepid & indefatigable adv5tur]s grappl$ ) !m & ma/]$ !m all4 ,n[ y1 :o h 9 y\r own homes se5 pictures transmitt$ across ! ocean by satellite1 c le>n fir/ h& f ! m5 :o work$ on h>d & v>i$ te*nical problems j :at ^! problems 7 & h[ !y 7 solv$4 ,&1 by read+ y c f9d out :at sort ( k1 tra9+1 & habits y y\rself w ne$ if y wi% "s day to adv5ture into ^? undiscov]$ or unexplor$ fields ( te*nology :i* w be new & excit+ :5 ,tel/> has become old hat4 ,june #e1 #aifc ,high ,s*ool ,sci5ce ,tea*+ ,aids ,prep>$ by ,bell ,telephone ,laboratories ,classroom units includ+ books1 motion pictures1 & demon/ration devices3 ,simil>ities 9 ,wave ,behavior ,f]romagnetic ,doma9s ,! ,spee* ,*a9 ,bell ,sy/em ,sci5ce ,exp]im5ts = ! advanc$ /ud5t3 ,f ,sun to ,s\nd ,sol> ,en]gy ,exp]im5t ,spee* ,syn!sis ,in=mation ab\t ^! & o!r mat]ials is available to tea*]s f local ,telephone ,company bus9ess (fices ,cont5ts ,introduction #h "p #a3 ,satellite ,communications #aj ,ronald ,m4 ,fo/]1 ,jr41 ,editor "p #b3 ,satellite ,communications ,case ,hi/ories #ch #a4 ,franz ,t4 ,geyl+ ,h[ ,d ,we ,calculate a ,satellite's ,orbit8 #da #b4 ,pet] ,hrycak ,:at ,color ,%\ld a ,satellite ,be8 #dh #c4 ,je(ry ,s4 ,c\rtney-pratt ,h[ ,c ,we ,make ,optical ,measurem5ts on a ,satellite8 #ec #d4 ,k5ne? ,d4 ,smi? ,h[ ,d ,we ,keep ,sol> ,cell ,p[] ,plants ,work+ 9 ,space8 #fb #e4 ,pet] ,d4 ,brick] ,w\ld ,"t ,delay ,be a ,problem 9 ,us+ a ,syn*ron\s ,satellite8 #gj #f4 ,e4 ,j>$ ,reid ,h[ ,c ,we ,repair an ,orbit+ ,satellite8 #gh ,sugge/$ ,read+ #hg ,introduction ,despite ! title1 ?is is n a physics textbook1 & x w tell y only "p ( ! fasc9at+ /ory ( satellite communications4 ,h[ev]1 we h tri$ to tell ?is /ory 9 a r special way4 ,"p ,i expla9s :y we are s int]e/$ 9 communicat+ by means ( man-made satellites1 describes ! important ev5ts 9 ! progress ( satellite communications 7) special emphasis on ,project ,tel/>71 & po9ts out "s ( ! v knotty problems t _h to be solv$4 ,!n1 9 ,"p ,,ii1 we pick out six typical satellite communications problems & g into !m m deeply4 ,^! case hi/ories are examples ( ! ?+s sci5ti/s & eng9e]s are con/antly fac$ )4 ,to n>rate !m we h call$ on six exp]ts--,bell ,telephone ,laboratories eng9e]s & sci5ti/s :o actually h be5 work+ on ! problems4 ,! second half ( our book is tak5 up by _! acc\nts ( _! own p]sonal exp]i5ces4 ,we hope t read+ !m w give y an insight into :at x is really l to be a sci5ti/ or eng9e] work+ 9 a laboratory on an important new v5ture into ! future4 ,we hope y w see t :at !y d is n all excitem5t & glam\r4 ,x involves h>d "w1 +5i\s ?9k+1 & plugg+ away at t\gh problems4 ,b ?is is :at sci5ti/s & eng9e]s enjoy--along ) ! excitem5t & glam\r1 ( c\rse4 ,only a "p ( :at our au?ors talk ab\t c /rictly be call$ 8physics0--x is also eng9e]+1 *emi/ry1 ma!matics1 & ev5 psy*ology4 ,b almo/ all _! "w is bas$--:5 y get d[n to fundam5tals--on basic pr9ciples ( classical physics taught 9 high s*ool4 ,n[1 a ^w ( caution4 ,9 ,"p ,i1 9 talk+ ab\t satellite communications 9 g5]al1 we h kept ?+s at a level t %\ld be und]/&able to almo/ ev]yone--ev5 ^? :o h nev] tak5 a high s*ool sci5ce c\rse4 ,b we w>n y ?is isn't true ( ,"p ,,ii4 ,our au?ors h tri$ to tell _! /ories z c>efully & z logically z possible1 b "s read]s may h tr\ble 9 foll[+ all !y say4 ,?is we expect4 ,we hav5't tri$ to sug>-coat or gloss ov] any ess5tial details ( ! problems or _! solutions4 ,we don't want y to ?9k t solv+ !m 0 any easi] ?an x actually 04 ,&1 s9ce ?is is n int5d$ z a textbook1 we may sometimes omit elem5t>y mat]ial & g "r to ! he>t ( ! matt]4 ,:5 ?is book 0 writt5 satellite communications 0 /ill a te*nological infant4 ,x is gr[+ & *ang+ s swiftly t mu* ( :at we say may soon be out ( date4 ,t c't be help$1 ( c\rse1 & we ask y--:o may be read+ x long aft]w>d--to be tol]ant4 ,our problems may well be =gott5 :5 new1 m sophi/icat$ ones appe>4 ,b we are deal+ "h 9 me?ods1 n 9 hi/ory2 ! ways 9 :i* ^! problems 7 attack$ are j z la/+ & important z ! problems !mselves4 "p #a ,satellite ,communications ,illu/ration3 ,title image 8,our int5sive rese>* & developm5t 9 ! field ( communications satellites h br\ght u to ! po9t :]e we are n[ c]ta9 ( ! te*nical feasibility ( transmitt+ messages to any "p ( ! _w by direct+ !m to satellites4444 ,! actual op]ation ( su* a sy/em w\ld provide a dramatic demon/ration ( our lead]%ip 9 ?is area ( space activity4444 ,! direct b5efits--economic1 educational1 & political--( ?is improv$ _w-wide communication w be invaluable40 --,,john ,f4 ,,k5n$y ,:y ,d ,we ,bo!r ,) ,satellite ,communications8 ,t's a good "q to beg9 )4 ,:y %\ld we get involv$ 9 a va/1 complicat$ program su* z communication by means ( man-made satellites8 ,is ! end result really wor? all ! tr\ble t is involv$8 ,z y g fur!r1 y w see t no?+ to d ) satellite communications is z simple z x fir/ seems4 ,ev5 "s ( ! easi] que/ions h be5 answ]$ only aft] long h\rs ( p]ceptive ?9k+1 +5i\s exp]im5t+1 & %rewd d$uction4 ,!y h requir$ a lot ( h>d "w1 l$ to _m fru/rat+ difficulties1 & co/ q a bit ( money4 ,b ! answ] /ill is yes4 ,despite all ! difficulties1 x is cle> t ! creation ( a successful satellite communicat+ sy/em is wor? x4 ,!re is a d\ble reason = ?is4 ,on ! "o h&1 x is a te*nological t>get t is n[ cle>ly )9 our range4 ,we mu/ ei!r rea* x or let progress pass u by4 ,satellite communications is "o field 9 :i*1 z f> z we "k1 ,am]ican eng9e]+ & sci5ce h be5 well 9 ! lead--s we h an ev5 great] inc5tive to press on 9 ?is direction z h>d & z fa/ z we c4 ,b p]haps m important ?an ! pre/ige x w\ld give our c\ntry is a second reason = our great int]e/ 9 satellite communications3 ,we ne$ x4 ,! _w today is go+ ?r\gh "o ( its great p]iods ( *ange4 ,?is has caus$ _m complications1 & "o ( ! mo/ important is ! ne$ = mu* bett] communications betwe5 nations & peoples4 ,by 8communications0 we mean all ! v>i\s ways ( s5d+ in=mation f "o place to ano!r3 mail1 telephone calls1 bus9ess data1 radio1 television4 ,! dem& = ^! s]vices--especially :5 we look ahead to ! #aigj's & #aihj's--w be trem5d\s4 ,our int]national communications *annels w be completely swamp$ unless "s major improvem5ts are made4 ,=tunately1 mod]n te*nology--giv5 a boo/ by ! _w's int]e/ 9 rockets1 missiles1 & ! exploration ( space--has %[n u "o answ] to ?is problem3 ! communications satellite4 ,! conv5tional pa?ways = long-di/ance communication h l$ along ! e>?'s surface1 "u ! oceans1 & ?r\gh ! l[] atmosph]e4 ,no "o ( ^! r\tes has yet provid$ all ! capacity1 spe$1 or quality we ne$4 ,pres5t und]seas cables h a limit$ capacity2 surface travel by %ip is too sl[ = any?+ b r\t9e mail2 %ort-wave radio is subject to di/ortion & noise1 & ! available frequ5cies are rapidly be+ us$ up4 ,al?\gh jet planes c span ! oceans 9 a few h\rs ) mail & su* ?+s z tap$ television %[s1 ! big ne$ w be to s5d in=mation in/antane\sly4 ,& ! communications satellite (f]s u a v promis+ way to d ?is4 ,:at a ,communications ,satellite ,c ,d ,"o ( ! attractive ?+s ab\t us+ a satellite is t x doesn't require a revolution>y break?r\gh 9 te*nical k4 ,x c employ a satisfactory means ( communicat+ t is already available3 ! micr[ave radio relay4 ,today1 ?is k9d ( transmission is us$ on a r\t9e basis to s5d ?\s&s ( telephone calls & television programs across long di/ances4 ,x gives high-quality p]=mance & has a l>ge message capacity4 ,b !re has always be5 "o difficulty keep+ u f us+ x = ov]seas communications3 ,extremely high frequ5cy waves c travel almo/ unlimit$ di/ances1 b !y c g only 9 /raight l9es4 ,?is means t ! curvature ( ! e>? limits a micr[ave's l9e-(-sight pa? to ab\t #cj miles2 s we mu/ build a s]ies ( transmission relay t[]s spac$ e #cj miles or s4 ,obvi\sly1 ?is isn't possible :5 y s5d messages across an ocean4 ,b1 if we c\ld f9d a way to s5d a signal high up into ! sky & !n b\nce x f !re back aga9 to a f>-(f spot1 we c\ld s5d micr[ave messages great di/ances4 ,illu/ration3 ,curvature ( ! e>? requires micr[ave t[]s to be ab\t #cj miles ap>t ,illu/ration3 ,micr[aves s5t via an orbit+ satellite c travel va/ di/ances ,z long ago z #aide1 ,ar?ur ,c4 ,cl>ke1 an ,engli% writ] & sci5ti/1 propos$ t a man-made satellite orbit+ 9 space might be us$ to relay signals 9 ?is way4 ,9 #aide1 ( c\rse1 ! v idea ( gett+ a satellite out into space seem$ utt]ly fanta/ic1 & satellite communications c\ld only be classifi$ z sci5ce fiction4 ,t5 ye>s lat]1 al?\gh ,sputnik ,i _h n yet be5 laun*$1 artificial satellites 7 close to reality4 ,at t "t1 ,john ,r4 ,pi]ce ( ,bell ,telephone ,laboratories made ! fir/ s]i\s /udy ( :at w\ld h to be done to build a work+ satellite communication sy/em--assum+ x ev] became possible to put satellites into orbit4 ,& ,bell ,laboratories has be5 int]e/$ 9 satellite communications ev] s9ce4 ,! ,road to ,successful ,satellite ,communications ,) ! fir/ laun*+ ( a satellite into orbit by ! ,soviet ,union 9 #aieg1 ! real developm5t "w on satellite communications began4 ,by #aifj ,project ,e*o _h prov$ t signals c\ld be reflect$ (f a man-made satellite & receiv$ sev]al ?\s& miles away4 ,&1 9 #aifb1 ,project ,tel/> demon/rat$ to ! :ole _w t an active repeat] satellite c\ld s5d telephone calls1 data1 & television across ! ocean4 ,br++ satellite communications almo/ to reality has requir$ m ?an putt+ a man-made satellite into orbit ar\nd ! e>?4 ,j z important h be5 ! inv5tion & developm5t ( _m rem>kable new devices3 ! transi/or1 ! sol> cell1 ! travel+ wave tube1 ! horn-reflector ant5na1 ! waveguide1 ! solid-/ate mas]1 & ! electronic comput]--to m5tion only "s ( ! m important4 ,)\t !m x w\ld /ill be impossible to f9d a t9y spe$+ object miles out 9 space1 s5d signals to x1 amplify !m billions ( times1 & !n return !m to di/ant po9ts on ! e>?4 ,"s ( ! new devices t help make satellite communications possible ,illu/ration3 horn-reflector ant5na ,illu/ration3 travel+-wave tube ,illu/ration3 transi/or ,illu/ration3 sol> cell ,illu/ration3 solid-/ate mas] ,:5 y look back at x1 we h se5 rem>kable progress 9 satellite communications--& "w is /ill cont9u+ at a fa/ pace4 ,"s ( ! mile/ones h be5 ^!3 ,,octob] #aide ,ar?ur ,c4 ,cl>ke publi%es 8,extra-,t]re/rial ,relays--,c ,rocket ,/ations ,give ,_w-,wide ,radio ,cov]age80 9 ,wireless ,_w1 sugge/+ ! use ( satellites = communications4 ,,janu>y #aa1 #aidf ,project ,diana ( ! ,u4 ,s4 ,army ,signal ,corps b\nces micr[ave rad> signals (f ! moon & back to ! e>?1 prov+ t relatively l[ p[] c transmit signals ov] v long di/ances4 ,,april #aiee ,john ,r4 ,pi]ce publi%es 8,orbital ,radio ,relays0 9 ,jet ,propulsion1 po9t+ out ! requirem5ts = a satellite communications sy/em4 ,,july #bi1 #aieh ,congress passes ! ,national ,a]onautics & ,space ,act1 sett+ up ! ,national ,a]onautics & ,space ,adm9i/ration 7,,nasa71 ) satellite communications exp]im5tation z "o ( its int]e/s4 ,,decemb] #ah1 #aieh ,score1 ! fir/ communications satellite1 is laun*$ by ! ,u4 ,s4 ,air ,=ce4 ,x is equipp$ ) tape record] units t transmit pr]ecord$ messages back to ! e>? ^u receipt ( signals4 ,on ,decemb] #ai a ,*ri/mas greet+ to ! _w record$ by ,presid5t ,eis5h[]--! fir/ message f a satellite to ! e>?--is transmitt$4 ,score cont9ues to transmit = #ab days be=e its batt]ies become too weak = fur!r use4 ,illu/ration3 uncaption$ ,,novemb] #bc1 #aiei ,live voice transmission is accompli%$ f ,bell ,telephone ,laboratories 9 ,holmdel1 ,new ,j]sey1 via ! moon to ,jet ,propulsion ,laboratories 9 ,gold/one1 ,cali=nia4 ,?is is ! fir/ ( #ag te/s 9 ,project ,moonb\nce1 all us+ ! moon z a reflector4 ,,july #h1 #aifj ,! ,bell ,sy/em proposes to ! ,f$]al ,communications ,commission a detail$ plan = a _w-wide communications sy/em us+ active repeat] satellites to provide telephone circuits & facilities = transmitt+ television to v>i\s p>ts ( ! _w4 ,,augu/ #ab1 #aifj ,e*o ,i is laun*$ into orbit by ,,nasa4 ,project ,e*o c>ries on a l>ge numb] ( communications exp]im5ts &1 mo/ important1 proves t x is practical to use a man-made satellite to reflect two-way telephone conv]sations across ! ,unit$ ,/ates4 ,e*o also dramatizes ! possibilities ( satellites = communications4 ,s9ce x is a #ajj-;foot inflat$ balloon made f alum9um-coat$ ,myl>1 x is l>ge en\gh to be se5 by ! nak$ eye4 ,p ?r\gh\t ! _w see ,e*o ,i sail on s*$ule across ! sky 9 its #ajjj-mile-high circul> orbit4 ,?ree ye>s lat]1 al?\gh x is n[ wr9kl$ & deflat$1 ! balloon is /ill 9 orbit4 ,illu/ration3 uncaption$ ,project ,e*o provid$ valuable data = future "w 9 satellite communications4 ,x demon/rat$ t a passive satellite--t is1 "o t simply reflects ! micr[ave signals x receives f an e>? /ation back to ano!r po9t--w\ld "w4 ,two-way conv]sations ( good quality 7 s5t betwe5 ! ,bell ,laboratories ,holmdel /ation & ,jet ,propulsion ,laboratories 9 ,gold/one1 & successful transmission 0 made to o!r po9ts 9 ! ,unit$ ,/ates & ,europe4 ,a scal$-up horn-reflector ant5na prov$ itself4 ,a me?od ( receiv+ micr[ave signals t _h be5 little us$ until !n1 kn[n z frequ5cy modulation ) fe$back 7,,fmfb71 p]=m$ v well4 ,new types ( l[-noise amplifi]s us+ solid-/ate mas]s gave excell5t results4 ,& track+ ( ! satellite by electronic comput]s1 by rad>1 & by telescope prov$ to be extremely reliable4 ,illu/ration3 uncaption$ ,,octob] #d1 #aifj ,c\ri] ,i-,b is laun*$ by ! ,army ,signal ,corps into a #ejj- to #fej-mile-high orbit4 ,a sph]e weigh+ #ejj p\nds & measur+ #ea in*es 9 diamet]1 ! ,c\ri] satellite is p[]$ by #bj1jjj sol> cells & conta9s f\r receiv]s1 f\r transmitt]s1 & five tape record]s4 ,x is design$ to demon/rate ! possibility ( us+ active repeat]s = delay$ transmission ( messages4 ,signals are receiv$1 /or$ on ! tapes1 & !n retransmitt$ back to e>? :5 ! satellite has mov$ on4 ,aft] #ah days 9 orbit1 te*nical difficulties end$ ,c\ri]'s ability to s5d signals1 b x receiv$ & retransmitt$ #aah million words dur+ its active life4 ,illu/ration3 uncaption$ ,,janu>y #ai1 #aifa ,! ,am]ican ,telephone & ,telegraph ,company is au?oriz$ by ! ,f$]al ,communications ,commission to e/abli% an exp]im5tal satellite communications l9k across ! ,atlantic4 ,two #agj-p\nd satellites are to be laun*$ by ,,nasa b w be design$1 built1 & paid = by ,,at,t4 ,?is project is lat] giv5 ! "n 8,tel/>40 ,,may #ah1 #aifa ,,nasa selects ! ,radio ,corporation ( ,am]ica to design & build ! ,relay satellite1 :i* w be us$ to te/ ! feasibility ( transoceanic telephone1 telegraph1 & television communications4 ,,augu/ #aa1 #aifa ,,nasa aw>ds ! ,hughes ,aircraft ,corporation a contract to build ,syncom1 an exp]im5tal active satellite to be plac$ into a #bb1cjj-mile-high orbit t w be syn*ron\s ) ! rotation ( ! e>?4 7,see page #cg = def9itions ( v>i\s k9ds ( satellite orbits47 ,,decemb] #bj1 #aifa ,! ,unit$ ,nations adopts a resolution on ! peaceful uses ( out] space t includes a reque/ = _w coop]ation 9 develop+ a sy/em ( communications satellites4 ,bo? ! ,unit$ ,/ates & ! ,soviet ,union sign ! resolution4 ,,febru>y #g1 #aifb ,presid5t ,k5n$y ask$ ,congress to pass a bill sett+ up a corporation to op]ate a satellite communications sy/em4 ,! propos$ corporation w\ld be own$ jo9tly by ! public at l>ge & ! c\ntry's communications common c>ri]s4 ,,july #aj1 #aifb ,project ,tel/> is successful4 ,= ! fir/ "t1 voice communications & live television are transmitt$ across ! ,atlantic via a man-made satellite t picks up signals s5t f "o cont95t1 amplifies !m1 & retransmits !m to ano!r cont95t4 7,on pages #ba to #cc we talk at fur!r l5g? ab\t ,project ,tel/>47 ,illu/ration3 uncaption$ ,,augu/ #ca1 #aifb ,presid5t ,k5n$y signs ! ,communications ,satellite ,act1 e/abli%+ a private corporation "u gov]nm5t regulation--! ,communications ,satellite ,corporation--:i* w plan1 own1 & op]ate a comm]cial satellite communications sy/em4 ,illu/ration3 uncaption$ ,,decemb] #ac1 #aifb ,relay ,i is laun*$ by ,,nasa4 ,simil> 9 _m ways to ! ,tel/> satellite1 x is an active repeat] device t picks up telephone1 television1 & o!r electronic signals & retransmits !m to a di/ant po9t4 ,relay also provides ! fir/ satellite communications l9k betwe5 ,nor? & ,s\? ,am]ica4 ,! satellite is a tap]$ cyl9d] #cc in*es long weigh+ #agb p\nds4 ,a ma/-l ant5na at "o end is us$ to receive & transmit a s+le television broadca/ or #ab simultane\s two-way telephone conv]sations4 ,f\r :ip ant5nas at ! o!r end ( ! cyl9d] h&le control1 track+1 & telemetry--turn+ exp]im5ts on & (f & s5d+ in=mation on ! behavior ( its compon5ts & on ! am\nt ( radiation x enc\nt]s 9 space4 ,relay is p[]$ by nickel-cadmium /orage batt]ies t are *>g$ by m ?an #h1jjj sol> cells m\nt$ on its eight sides4 ,x conta9s two id5tical receiv+1 amplify+1 & transmitt+ sy/ems call$ transpond]s1 ea* ) an output ( #aj watts4 ,relay ,i is travel+ 9 an orbit t ranges f #hbj to #d1fab miles high1 & circles ! e>? ab\t e #ahe m9utes4 ,soon aft] x is laun*$1 ,relay's telemetry reports tr\ble 9 ! voltage regulator ( "o ( ! transpond]s1 :i* causes excessive p[] dra94 ,on ,janu>y #c1 #aifc1 ! alt]nate transpond] is swit*$ on1 & a successful s]ies ( te/s--includ+ live television broadca/s betwe5 ! ,unit$ ,/ates & ,europe--beg9s4 ,,janu>y #d1 #aifc ,! ,tel/> ,i satellite1 :i* = almo/ two mon?s c\ld n be turn$ on to transmit communications signals1 is reactivat$ by ,bell ,laboratories eng9e]s4 7,! /ory ( ?is +5i\s electronic detective "w is told 9 detail on pages #gh to #he47 ,,febru>y #ad1 #aifc ,! fir/ ,syncom satellite is laun*$ by ,,nasa1 b its communications sy/ems d n op]ate4 ,x is ! fir/ satellite to try = a syn*ron\s pa?1 revolv+ ar\nd ! e>? once e #bd h\rs & ?us appe>+ to hov] cont9u\sly ov] ! same longitude4 ,syncom is a %ort cyl9d] #bh in*es 9 diamet] & #ae in*es long1 & weighs #hf p\nds4 ,l ,tel/> & ,relay1 x is p[]$ by a comb9ation ( sol> cells & nickel-cadmium batt]ies1 b x is design$ to h&le only "o two-way telephone conv]sation & _c transmit television4 ,illu/ration3 uncaption$ ,,may #g1aifc ,! ,tel/> ,,ii satellite is laun*$ = ! ,bell ,sy/em by ,,nasa4 7,see page #ca47 ,:at ,ab\t ! ,future8 ,z ?is is writt5 7,june #aifc71 second ,relay & ,syncom laun*+s are 9 ! (f+4 ,& !re are plans = m exp]im5tation ) passive satellites1 includ+ a new1 m ne>ly rigid ,e*o balloon4 ,fur!r 9 ! future1 /udies are go+ on ( a propos$ ,int]m$iate ,altitude ,communications ,satellite = milit>y use 9 ! #f1jjj- to #aj1jjj-mile-high range 7beyond t ( ,tel/> & ,relay7 & ,advanc$ ,syncom1 a syn*ron\s satellite ( increas$ capacity4 ,"w is also cont9u+ to acquire new te*nical k t w be ne$$ 9 ! future--su* z v>i\s me?ods ( keep+ satellites /abiliz$ 9 space & new ways ( supply+ p[]1 includ+ improv$ sol> cells & ! use ( radioisotopes4 ,! ultimate goal1 ( c\rse1 is a work+ comm]cial communications satellite sy/em4 ,exactly :5 ?is w be a reality--& :at =m x w take--are que/ions ^: answ]s /ill lie ahead ( u4 ,illu/ration3 ,! orbits ( f\r communications satellites v>y 9 size & %ape ,e*o ,i #ajjj miles #ajjj miles ,relay ,i #dfab ,miles #hbj miles ,tel/> ,i #ceca miles #eib miles ,tel/> ,,ii #ffig miles #fjd miles ,project ,tel/> ,9 ?is section we w g into "s detail ab\t ,project ,tel/>4 ,we d ?is because mu* ( :at we le>n$ f ?is project applies to ! g5]al field ( satellite communications4 ,! problems t 7 fac$ & solv$ are typical ( ! *all5ges t work+ eng9e]s & sci5ti/s mu/ meet today4 ,& !re is1 ( c\rse1 ano!r reason to put ?is mu* emphasis on ,tel/>3 ,! six case hi/ories 9 ,"p ,,ii ( our book 7 writt5 by m5 :o 7 involv$ ) t project4 ,be=e read+ _! acc\nts x w be helpful = y to h "s backgr\nd in=mation ab\t x4 ,:at ,project ,tel/> ,0 ,design$ ,to ,d ,ev5 its mo/ en?usia/ic plann]s at ,bell ,telephone ,laboratories nev] expect$ ! s5sation t ,tel/> caus$4 ,al?\gh x 0 a deadly s]i\s v5ture--"o ( ! /eps along ! way t[>d putt+ toge!r a workable satellite communications sy/em--its success made x ! inspiration1 among o!r ?+s1 ( c>toons1 jokes1 & a c\ple ( popul> songs4 8,tel/>0 soon became a "n recogniz$ ar\nd ! entire globe4 ,/ories ab\t ,project ,tel/> appe>$ 9 newspap]s 9 almo/ e language1 9 *ildr5's books1 9 wom5's fa%ion magaz9es4 ,illu/ration3 ,on ,july #aj & #aa1 #aifb1 p on two cont95ts saw ^! sc5es on television at ! same "t1 ) ! aid ( ! ,tel/> ,i satellite ,:at caus$ all ?is /ir 9 ! summ] & fall ( #aifb8 ,! answ]--n[ t we look back on x--seems r cle>3 ,= ! fir/ "t1 ! :ole _w discov]$ t satellite communications 0 really possible--t peoples sep>at$ by oceans c\ld n[ be unit$ by live television4 ,space _h become an adv5ture1 n j = lonely a/ronauts1 b = ev]yone "r 9 8 liv+ room4 ,project ,tel/>1 ( c\rse1 _h m s]i\s objectives3 --to prove t a broadb& communications satellite c\ld transmit telephone messages1 data1 & television2 --to te/1 "u ! /resses ( an actual laun* & ! haz>ds ( space1 "s ( ! electronic equipm5t t _h be5 develop$ = satellite communications2 --to measure ! radiation t a satellite w\ld meet 9 space2 --to f9d out ! be/ ways to track a mov+ satellite accurately2 --to provide a real-life te/ = ! special satellite communications ant5nas & o!r gr\nd /ation equipm5t4 ,to d its pr9cipal job--communications--! ,tel/> ,i satellite _h to receive a signal f a gr\nd /ation1 amplify x1 & !n retransmit x on a diff]5t frequ5cy back to o!r po9ts on ! e>?4 ,?is signal _h to be /rong en\gh & good en\gh to be receiv$ & und]/ood on ! gr\nd4 ,to d its second>y job--measure radiation & o!r conditions 9 space--! satellite _h to be equipp$ ) special te/+ devices & _h to h a means ( report+ facts ab\t ! environm5t x enc\nt]$ 9 space & ! effects ( radiation on sol> cells & transi/ors4 ,to let u "k h[ well its equipm5t 0 work+1 ! satellite _h to record & transmit a l>ge numb] ( measurem5ts--includ+ su* ?+s z ! temp]ature & pressure inside ! satellite1 its ori5tation ) respect to ! sun1 ! curr5t & voltage 9 v>i\s p>ts ( its electronic circuitry4 ,s5d+ ^! measurem5ts back to a gr\nd /ation is call$ telemetry4 ,to help ) track+1 ! satellite _h to h a cont9u\s radio beacon signal t c\ld be easily pick$ up on e>?4 ,f9ally1 ! satellite _h to be able to control its equipm5t by means ( signals f ! gr\nd4 ,to keep ! sol> p[] plant f be+ ov]load$1 !re _h to be "s way ( 8comm&+0 ! satellite to turn itself on or (f4 ,z y w read lat]1 ?is 0 ! "o "p ( ! satellite t caus$ u ! mo/ heada*es once ,tel/> ,i got into orbit4 ,! ,tel/> ,i ,satellite--,outside ,tel/>'s out] appe>ance is v famili> by n[3 a #cd-;in* sph]e ) #gb flat facets1 a d\ble r[ ( rectangul> op5+s circl+ its c5t]1 & a %ort1 oddly twi/$ ant5na on "o end4 ,( ! #gb facets1 #fj are us$ = ! sol> cells t are ! satellite's ma9 p[] s\rce4 ,:5 ,tel/> is 9 sunlight1 ^! cells conv]t sol> en]gy into electrical p[]2 at full capacity ! #cfjj sol> cells w supply ab\t #ae watts4 ,z "t goes by1 ?is p[] sl[ly dim9i%es z ! cells are gradually damag$ by su* haz>ds ( space z radiation p>ticles & micrometeorites4 ,to r$uce ?is damage1 ! satellite's cells are cov]$ ) a ?9 lay] ( man-made sapphire4 ,two b&s ( rectangul> op5+s g ar\nd ! c5t] ( ! satellite4 ,! small] cavities1 ( :i* !re are #gb1 are receiv+ ant5nas2 ! #dh l>g] ones are transmitt+ ant5nas4 ,?is arrangem5t all[s ! ant5nas to transmit & receive equally well 9 all directions--except directly along ! satellite's poles4 ,at "o end ( ! satellite is an entirely sep>ate receiv+ & transmitt+ ant5na t takes c>e ( all ! signals ne$$ = ,tel/>'s comm&1 track+ & telemetry4 ,! ant5na is compos$ ( f\r metal loops jo9$ 9 ! %ape ( a helix4 ,x receives ! important comm& signals f ! gr\nd t give ord]s to ! satellite's equipm5t4 ,x s5ds reports back to ! gr\nd f ! special radiation measur+ devices & o!r s5sors abo>d ! satellite1 & x also transmits ! cont9u\s #acf-megacycle radio beacon t c be pick$ up by gr\nd equipm5t se>*+ = ,tel/>4 ,six ( ! satellite's flat facets are us$ = special measur+ devices4 ,two diff]5t radiation /udies are made3 f9d+ out h[ mu* damage w be done to sol> cells & transi/ors1 & det]m9+ h[ _m actual en]getic p>ticles--protons & electrons--are pres5t 9 ! "p ( space t ,tel/> passes ?r\gh4 ,^! diff]5t jobs are done by special devices on v>i\s facets4 ,"o1 = example1 consi/s ( sev5 id5tical silicon transi/ors1 six hav+ diff]5t ?icknesses ( %ield+ & "o be+ left un%ield$--! am\nt ( damage done to ea* is record$ & report$ back to e>?4 ,devices on ano!r facet measure ! radiation damage to sol> cells protect$ by v>i\s ?icknesses ( sapphire4 ,= ! second radiation exp]im5t--p>ticle c\nt+--f\r diff]5t types ( silicon diodes are us$ z p>ticle detectors4 ,^! measure ! en]gy deposit$ bo? by protons ( ?ree en]gy levels & by electrons z ! satellite passes ?r\gh belts ( natural & man-produc$ radiation 9 space4 ,illu/ration3 ,! ,tel/> ,i satellite--outside telemetry1 comm& & beacon ant5na sol> cells = p[] supply sol> cells to measure radiation damage receiv+ ant5na transmitt+ ant5na transi/ors us$ to measure radiation damage sol> aspect cells mirror ,illu/ration3 ,! ,tel/> ,i satellite--inside 7look+ at ! electronics cani/] f ! top d[n7 beacon transmitt] travel+-wave tube amplifi] radiation measurem5t equipm5t nickel-cadmium cells 7foam$7 ,measur+ devices m\nt$ on ! surface ( ! ,tel/> ,i satellite ,illu/ration3 p>ticle detectors us$ to c\nt protons ,illu/ration3 transi/ors us$ to measure radiation damage ,illu/ration3 sol> cells us$ to measure radiation damage & z sol> aspect indicators ,illu/ration3 p>ticle detector us$ to c\nt electrons ,!re are two o!r special devices3 ,six s+le sol> cells are spac$ at regul> int]vals ar\nd ! satellite2 ^! 8sol> aspect0 indicators report ! quantity ( sunlight hitt+ !m--& ?us tell ! direction 9 :i* ! satellite is po9t+4 ,?ree highly poli%$ metal mirrors are also plac$ on ,tel/>2 fla%es ( sunlight reflect$ f !m c be se5 9 a telescope4 ,to give a precise indication ( ! satellite's position1 ! data obta9$ f bo? ! sol> aspect cells & f ! fla%es (f ! mirrors are comb9$4 ,! ,tel/> ,i ,satellite--,inside ,)9 ! :ite alum9um-oxide out] %ell ( ! satellite is cramm$ a complicat$ array ( electronic equipm5t4 ,surpris+ly1 mo/ ( ?is ge> has to d n ) ,tel/>'s prime function--communications--b ) its comm& & telemetry sy/ems4 ,! reason is t ! satellite is an exp]im5tal device1 n j a spectacul> way to relay television programs4 ,altoge!r1 ! satellite's v>i\s electronic circuits conta9 m ?an a ?\s& transi/ors & almo/ #aejj semiconductor diodes1 plus a s+le electron tube--a travel+-wave tube us$ 9 ! communications amplifi]4 ,! satellite itself has a magnesium frame t is cov]$ ) alum9um panels4 ,all its electronic compon5ts are inside a alum9um cani/]1 #bj in*es 9 diamet]1 atta*$ to ! int]ior frame by special nylon lac+s t r$uc$ vibration inside ! cani/] dur+ laun*4 ,:5 all ! compon5ts & subassemblies _h be5 c>efully put 9 place & ?or\ghly te/$1 ! cani/] 0 fill$ ) a liquid foam call$ polyure?ane4 ,?is mat]ial h>d5s into a v light & rigid solid1 completely envelop+ ! equipm5t & protect+ x f damage & vibration4 ,aft] ! cani/] 0 solidly foam$1 metal domes 7 weld$ onto ! ends1 & x 0 enclos$ 9 a _m-lay]$ blanket ( alum9um-coat$ ,myl> 7! same mat]ial us$ 9 ! ,e*o balloon74 ,to keep its temp]ature prop]ly controll$1 %utt]s on ! cani/]'s two ends are op]at$ by bell[s4 ,! satellite p[] sy/em includes m ?an j sol> cells4 ,:5 op]at+ at full capacity1 ! satellite's equipm5t ne$s m en]gy ?an ! #cfjj sol> cells c provide at "o "t4 ,s ,tel/> also uses a /orage batt]y made up ( #ai re*>geable nickel-cadmium cells design$ = ?is special purpose4 ,^! ensure t ! satellite has a cont9u\s & suffici5t supply ( p[]1 ev5 :5 all equipm5t is 9 op]ation or :5 ! satellite is pass+ ?r\gh ! e>?'s %ad[4 ,illu/ration3 ,aft] all electrical te/s _h be5 made on ! satellite's compon5ts1 ! electronics cani/] 0 fill$ ) liquid polyure?ane foam1 us+ ?is specially develop$ foam ma*9e ,illu/ration3 ,! giant horn ant5na at ,&ov]1 ,ma9e ,gr\nd ,/ations = ,satellite ,communications ,project ,tel/> is actually an ext5sion into space ( micr[ave communications me?ods t h be5 ?or\ghly prov$ on ! gr\nd4 ,= ,project ,e*o & o!r e>ly exp]im5ts 9 satellite communications1 ,bell ,laboratories built a l>ge ant5na ( ! type kn[n z a horn-reflector 9 ,holmdel1 ,new ,j]sey4 ,= ,project ,tel/>1 a simil> b mu* l>g] ant5na 0 design$4 ,x 0 locat$ 9 a relatively isolat$ spot at ,&ov]1 9 ! we/]n "p ( ,ma9e1 :]e x w\ld be close to ,europe4 ,! site is nicely protect$ by a surr\nd+ r+ ( l[ hills--high en\gh to keep out int]f]+ radio signals1 b l[ en\gh n to block ! satellite :5 x is ne> ! horizon4 ,! giant ,&ov] horn is a /eel & alum9um /ructure #agg feet long & #id feet high t weighs #chj tons4 ,at "o end is a giant op5+ ( #cfjj squ>e feet2 f !re ! horn tap]s d[n to a cab 9 :i* ! v s5sitive receiv] & p[]ful transmitt+ equipm5t is locat$4 ,! entire ant5na--horn1 cab1 & support+ framework--moves smoo?ly on tracks t all[ x to rotate 9 a #cfj-;degree circle ar\nd its v]tical axis 7*ang+ azimu?74 ,x also c sw+ ab\t its horizontal axis f ! horizon up to ! z5i? 7*ang+ elevation74 ,despite its size1 ! ant5na c revolve /eadily & precisely 9 a complete circle 9 j f\r m9utes4 ,signals are beam$ to ! satellite on a frequ5cy ( #fcij megacycles1 us+ modifi$ ,bell ,sy/em micr[ave equipm5t & a special travel+-wave tube ) an output ( #b kil[atts4 ,signals come back on a #dagj-megacycle frequ5cy at a mu* l[] p[] level--z small z a trillion? ( a watt4 ,!y are amplifi$ by a ruby cry/al mas] t op]ates at ! temp]ature ( liquid helium--j a few degrees above absolute z]o4 ,! :ole ant5na /ructure & its associat$ equipm5t are enclos$ 9 a huge 8radome0--a bubble made f ,dacron & syn!tic rubb] only a sixte5? ( an in* ?ick b measur+ #baj feet 9 diamet] & #afj feet high4 ,x is "o ( ! l>ge/ air-support$ /ructures ev] erect$4 ,! ,&ov] gr\nd /ation includes a lot m equipm5t--mo/ ( x hav+ to d ) track+ ! satellite1 comput+ its orbits1 s5d+ & receiv+ comm& & telemetry signals1 & int]connect+ ! satellite ) regul> telephone & television l& l9ks4 ,mo/ ( ?is is locat$ 9 a control build+ ab\t a qu>t] mile f ! giant radome4 ,illu/ration3 ,! ,fr5* radome looms ov] ! ,brittany c\ntryside ,a gr\nd /ation v simil> to ! ,&ov] in/allation has be5 built by ! ,fr5* ,national ,c5t] ( ,telecommunications ,/udies at ,pleumeur-,bod\ 9 ,brittany4 ,! ,briti% ,g5]al ,po/ ,(fice has e/abli%$ a /ation at ,goonhilly ,d[ns 9 ,cornwall1 ,engl&1 :i* uses a l>ge1 deep p>abolic di% r ?an a horn-reflector ant5na4 ,bo? ,briti% & ,fr5* /ations p>ticipat$ 9 ! fir/ ,tel/> exp]im5ts4 ,satellite communications gr\nd /ations also h be5 set up 9 ,fuc9o1 ,italy1 & ne> ,rio de ,janeiro1 ,brazil1 & o!rs are "u con/ruction 9 ,we/ ,g]many & ,japan4 ,! ,satellite ,goes ,into ,orbit ,at #d3ce a4m4 7,ea/]n ,daylight ,"t7 on ,july #aj1 #aifb1 a ,?or-,delta rocket laun*$ ,tel/> ,i into its orbit1 almo/ exactly accord+ to plan1 f ! ,national ,a]onautics & ,space ,adm9i/ration's ,cape ,canav]al base4 ,on ,tel/>'s six? orbit ar\nd ! e>?--at #g3bf p4m4--! fir/ transmission to & f ! satellite took place4 ,dur+ ?is pass telephone calls1 television1 & photos 7 transmitt$ betwe5 ,&ov] & ,holmdel4 ,"s ( ^! signals 7 also pick$ up 9 ,europe4 ,on ! next day1 a tap$ television program 0 s5t f ,france to ! ,unit$ ,/ates1 & a live program came f ,engl& via ,tel/>4 ,dur+ ! next f\r mon?s1 m ?an #djj transmissions 7 h&l$ by ,tel/>--includ+ #ej television demon/rations 7bo? black-&-:ite & color71 ! s5d+ ( telephone calls & data 9 bo? directions1 & ! relay+ ( facsimile & telephotos4 ,9 addition1 ! satellite p]=m$ m ?an #cjj valuable te*nical te/s4 ,almo/ all ( !m %[$ rem>kably successful results4 ,radio transmission 0 z good z 0 expect$4 ,tel/>'s communications equipm5t work$ exactly z x %\ld1 ) no damage f ! %ock & vibration ( ! laun*4 ,temp]atures inside ! satellite 7 kept "u good control4 ,! satellite 0 successfully /abiliz$--prev5t$ f tumbl+ ov] & ov]--by be+ spun ar\nd its pol> axis1 ) ! sp9 rate gradually decreas+1 z pr$ict$1 f its rate ( #agg4g revolutions p] m9ute j aft] laun*4 ,! sol> cells work$ almo/ exactly z expect$4 ,mu* extremely valuable data ab\t radiation 9 space 0 report$4 ,! gr\nd /ations accurately trac$ ! fa/-mov+ satellite 9 almo/ r\t9e fa%ion4 ,b x w\ld be ask+ too mu* to h ev]y?+ p]fect4 ,tel/> ,i unexpect$ly met radiation 9 space e/imat$ to be #ajj times m pot5t ?an _h be5 pr$ict$4 ,z a result1 difficulties arose dur+ ,novemb] #aifb 9 "s ( ! transi/ors 9 its comm& circuit--& on pages #gh to #he we tell y :at ^! problems 71 h[ !y 7 discov]$1 & :at /eps 7 tak5 to ov]come !m4 ,"s "t lat] ! satellite aga9 fail$ to respond to comm&s f ! gr\nd1 & on ,febru>y #ba1 #aifc1 x w5t sil5t4 ,illu/ration3 ,new gold-dom$ device on ! ,tel/> ,,ii satellite c measure electrons 9 an en]gy range f #gej ?\s& to #b million electron volts4 ,! ,second ,tel/> ,satellite ,on ,may #g1 #aifc1 ! ,tel/> ,,ii satellite 0 laun*$ into an elliptical orbit almo/ twice z l>ge z t ( ,tel/> ,i1 rang+ f an apogee ( #ffig miles to a p]igee ( #fjd miles4 ,! new satellite circles ! e>? once e #bbe m9utes4 ,! high] altitude provides ,tel/> ,,ii ) long] p]iods :5 x is visible at bo? ,&ov] & gr\nd /ations 9 ,europe1 & keeps x out ( ! high-radiation regions ( space = a great] "p ( ! "t4 ,! satellite itself is mu* ! same z ,tel/> ,i1 except = a few m9or *anges t make its weight #age r ?an #agj p\nds4 ,its radiation measur+ devices h a great] range ( s5sitivity1 & !re are six new measurem5ts to be report$ back to e>?4 ,telemetry c n[ be s5t on bo? ! micr[ave beacon &1 z be=e1 on ! #acf-megacycle beacon4 ,to help prev5t ! k9d ( damage t occurr$ 9 ! transi/ors ( ,tel/> ,i's comm& decod]s1 ,tel/> ,,ii uses a diff]5t type ( transi/or1 9 :i* ! gases h be5 remov$ f ! cap enclosures t surr\nd ! transi/or elem5ts4 ,a simplifi$ me?od ( op]ation = ! giant ,&ov] horn ant5na is n[ 9 op]ation1 ) ! autotrack alone be+ us$ = precise track+ & po9t+4 ,tel/> ,,ii's fir/ successful television transmission took place on ,may #g1 & a new s]ies ( te*nical te/s1 radiation measurem5ts1 & exp]im5ts 9 transoceanic communications has begun4 ,h[ ! ,tel/> ,satellite ,works ,a lot ( facts & figures sometimes lead only to confusion1 b ^! pages may help make ?+s cle>]4 ,"h y c see--/ep by /ep--exactly :at happ5s dur+ a typical pass ( ! ,tel/> satellite ov] ! ,&ov] gr\nd /ation3 ,illu/ration3 ,tel/> satellite at "w #a ,! satellite comes ov] ! horizon4 #b ,! comm& track]1 kn[+ f comput] data ! satellite's approximate location1 beg9s to se>* = its cont9u\s #acf-megacycle beacon4 ,a quad-helix ant5na 7f\r long spirals7 tracks ! satellite to an accuracy ( "o degree4 #c ,:5 ! satellite is locat$1 ! comm& transmitt] turns on ! satellite's transi/or circuits & telemetry4 ,! gr\nd /ation !n *ecks on ! satellite's op]at+ condition1 z report$ by telemetry4 #d ,! comm& transmitt] !n turns on ! satellite's travel+-wave tube1 :i* />ts ! transmission ( a #djhj-megacycle beacon signal4 #e ,! precision track]--an eight-foot p>abolic di% 7kn[n z a ,cassegra9ian ant5na7 m\nt$ on a pylon--locates ?is beacon & tracks x to )9 "o-fiftie? ( a degree4 #f ,! horn ant5na's autotrack me*anism1 :i* is po9t$ by bo? ! precision track] & data f magnetic tapes1 locates ! satellite's beacon signal4 #g ,n[ ! horn ant5na locks onto ! satellite1 ) ! autotrack cont9u+ to make f9e adju/m5ts 9 po9t+ ! horn4 #h ,! equipm5t is n[ ready = communications signals to be s5t f ! two-kil[att gr\nd transmitt] to ! satellite4 #i ,! satellite receives ! signals & conv]ts !m d[n to a frequ5cy ( #ij megacycles2 !y are amplifi$ 9 transi/or circuits & conv]t$ up to a new frequ5cy ( #dagj megacycles4 #aj ,! signals are amplifi$ aga9 by ! travel+-wave tube--= a total amplification ( z mu* z t5 billion times--to get a radiat$ p[] ( #b watts4 #aa ,! #dagj-megacycle signals are n[ transmitt$ 9 all directions by ! satellite's equatorial ant5na4 #ab ,^! signals c be pick$ up at ,&ov] or at any o!r gr\nd /ation equipp$ ) a suitable ant5na t is )9 l9e ( sight ( ! satellite4 #ac ,at ,&ov]1 ! receiv$ signals are amplifi$ by means ( a solid-/ate mas] & a frequ5cy-modulation-)-fe$back circuit4 #ad ,!y c n[ be relay$ via regul> l& l9es to _! de/9ation4 #ae ,ne> ! end ( a pass1 ! comm& track] turns (f ! communications circuits & telemetry 9 ! satellite4 #af ,! satellite drops bel[ ! horizon4 ,"s ,big ,problems 9 ,satellite ,communications ,we hope ! la/ few pages hav5't giv5 y a wrong impression ( satellite communications4 ,x is easy to assume1 :5 we li/ ! ord]ly1 /ep-by-/ep progress f purely !oretical ideas to a work+ satellite su* z ,tel/>1 t ev]y?+ has gone l clockwork4 ,t isn't ! case at all--& 9 ! re/ ( ?is book we are go+ to %[ y :y x isn't4 ,_m problems _h to be solv$2 _m sci5tific & te*nological advances _h to be made4 ,we t\*$ on a numb] ( ! problems ( satellite communications 9 our detail$ acc\nt ( ,project ,tel/>4 ,mo/ ( !m are n conf9$ to t project--!y are ! sorts ( que/ions t any complex advance 9 satellite communications w run into4 ,we w li/ "s ( ! m important ones "h4 ,!n1 9 ,"p ,,ii1 we w talk ab\t "s g5]al me?ods ( solv+ sci5tific & te*nological problems4 ,all ?is is a r r\ndab\t--b necess>y--way ( lead+ up to our ma9 int]e/3 ! acc\nts by six ,bell ,laboratories eng9e]s & sci5ti/s ( _! "w to solve "s typical problems 9 satellite communications4 ,! _m complications ( satellite communications c be divid$ into sev]al gr\ps4 ,fir/ ( all1 !re are ! problems involv$ 9 fitt+ satellite communications into an already e/abli%$ _w communications sy/em4 ,!re are1 next1 _m problems1 bo? small & l>ge1 9 design+ ! "r k9d ( satellite4 ,!re are ! problems ( laun*+ a satellite & gett+ x into ! prop] orbit4 ,!re are ! problems 9 mak+ sure x /ays 9 ! "r orbit once x gets !re4 ,&1 f9ally !re are ! problems 9 see+ t x cont9ues to d its job reliably4 ,9 ^! five categories !re are a lot ( specific que/ions t mu/ be answ]$ to plan a work+ satellite communications sy/em4 ,a li/ ( "s ( !m foll[s4 ,we hav5't attempt$ to cov] ev]y?+1 b ^! %\ld give y "s idea ( ! tasks & que/ions involv$ 9 plann+ an imm5se project l ?is4 ,g5]al ,problems ( a ,satellite ,communications ,sy/em ,:at jobs c\ld a communications satellite d be/8 ,%\ld x be us$ = television8 ,%\ld x c>ry telephone messages8 ,h[ _m8 ,w\ld x be m valuable = data transmission8 ,facsimile8 ,:at p>ts ( ! _w %\ld be cov]$8 ,c all ! problems ( int]national coop]ation be solv$8 ,w\ld a satellite t c\ld broadca/ directly to home receiv]s be possible8 ,:at milit>y uses c\ld a communications satellite sy/em s]ve8 ,w\ld a passive satellite--"o t reflects signals )\t amplify+ !m--be wor? develop+8 ,or %\ld ! emphasis be on active repeat]s1 :i* c receive1 amplify1 & retransmit signals8 ,:at k9d ( te*nical /&>ds %\ld be set z ! m9imums8 ,h[ detrim5tal is "t delay 9 s5d+ communications to a satellite & back8 ,:at k9d ( gr\nd transmitt]s & receiv]s w\ld be ne$$8 ,h[ p[]ful or s5sitive %\ld !y be8 ,:]e %\ld !y be locat$8 ,h[ _m satellites w\ld be ne$$8 ,h[ mu* w\ld all ?is co/8 ,satellite ,design ,problems ,h[ big %\ld a satellite be8 ,:at %\ld x be made (8 ,:at color %\ld x be8 ,:at k9d ( p[] supply %\ld x use8 ,h[ p[]ful %\ld its electronic equipm5t be8 ,:at %\ld be its message-h&l+ capacity8 ,:at are ! be/ receiv+ & transmitt+ ant5nas to use8 ,:at frequ5cies ought to be employ$8 ,:at k9d ( modulation %\ld be us$8 ,h[ %\ld signals be amplifi$8 ,:at k9d ( telemetry equipm5t w be ne$$8 ,h[ c radiation 9 space be measur$8 ,laun*+ & ,track+ ,problems ,h[ big a rocket boo/] w\ld be ne$$8 ,f :at "p ( ! _w %\ld a satellite be laun*$8 ,:at k9d ( orbit %\ld x g into8 7,see table bel[7 ,h[ f> up %\ld ! satellite g8 ,h[ c a satellite be track$ once x is 9 orbit8 ,h[ d we pr$ict future orbits ( a satellite8 ,ori5tation & ,control ,problems ,h[ c ord]s be giv5 to a satellite :ile x is 9 orbit8 ,if x is to /ay 9 a fix$ attitude1 h[ c x be kept !re8 ,:at c be done to keep a satellite prop]ly /abiliz$8 ,c optical measurem5ts be made on a satellite8 ,:at w be ! effects ( sunlight & gravity on its position 9 space8 ,problems ( ,reliability ,h[ long w ! satellite rema9 active8 ,:at factors w affect its s]vice life8 ,%\ld its equipm5t be made r$undant8 ,:at k9ds ( compon5ts w be mo/ reliable 9 space8 ,:at is ! be/ way to te/ its equipm5t be=e ! satellite is laun*$8 ,:at effects w radiation 9 space h on ! satellite8 ,h[ c its compon5ts be protect$ f ^! radiation effects8 ,h[ c x be insulat$ f extremes ( temp]ature8 ,:at c be done to protect ! satellite f ! %ock & vibration ( laun*+8 ,w x be possible to repair an orbit+ satellite8 ,c\ld a satellite be br\ght back f orbit to be repair$ or salvag$8 ,types ( ,satellite ,orbits ,circul> ,orbit--an orbit ^: altitude f ! e>? rema9s con/ant2 x makes a circle t has ! c5t] ( ! e>? z a c5t]4 ,elliptical ,orbit--an orbit ^: altitude f ! e>? v>ies f "o extreme to ano!r2 x makes an ellipse ) ! c5t] ( ! e>? z "o focus4 ,! orbit's l[e/ altitude is call$ ! p]igee1 its highe/ altitude is call$ ! apogee4 ,equatorial ,orbit--an orbit 9 ! plane ( ! e>?'s equator4 ,pol> ,orbit--an orbit 9 a plane =m$ by ! ,nor? & ,s\? ,poles4 ,syn*ron\s ,orbit--an orbit ^: p]iod is #bd h\rs1 ! same z t ( ! e>? revolv+ on its axis--s t ! satellite's & ! e>?'s angul> velocities are ! same4 ,al?\gh !re are _m possible k9ds ( syn*ron\s orbits1 ea* mu/ h an av]age altitude above ! e>?'s surface ( approximately #bb1cjj /atute miles4 ,/ation>y ,orbit--an orbit t is circul>1 equatorial1 & syn*ron\s--s t ! satellite w appe> /ation>y f any po9t on ! e>?4 ,incl9$ ,syn*ron\s ,orbit--an orbit t is syn*ron\s b n /ation>y1 s9ce x does n foll[ ! plane ( ! equator4 ,f a po9t on e>?1 x w appe> to foll[ a figure eight patt]n ab\t a l9e ( con/ant longitude4 "p #b ,satellite ,communications ,case ,hi/ories ,illu/ration3 ,title image ,six ,typical ,problems ,! que/ions we li/$ 9 ,"p ,i cov] a v broad area ( sci5ce & te*nology4 ,_! answ]s involve1 m ?an any?+ else1 physics1 electrical eng9e]+1 & me*anical eng9e]+4 ,"s1 h[ev]1 also require t ! m5 :o "w on !m "k *emi/ry1 metallurgy1 ma!matics1 & occasionally ev5 biology1 psy*ology1 geography1 & economics4 ,we obvi\sly c't %[ y h[ all ! problems 9 ,"p ,i c be solv$4 ,r1 we h pick$ six ( !m z examples4 ,!y are n necess>ily ! mo/ important ones1 b !y seem to u to be typical ( :at eng9e]s & sci5ti/s work+ 9 ! satellite communications program actually h to d4 ,^! are ! six problems we w be talk+ ab\t at l5g?3 --,h[ d we calculate a satellite's orbit8 --,:at color %\ld a satellite be8 --,h[ c we make optical measurem5ts on a satellite8 --,h[ d we keep sol> cell p[] plants work+ 9 space8 --,w\ld "t delay be a problem 9 us+ a syn*ron\s satellite8 --,h[ c we repair an orbit+ satellite8 ,z y c see1 we h pick$ problems t (f] a good deal ( v>iety4 ,"s ( !m h be5 satisfactorily solv$2 = o!rs ! solutions are n yet complete4 ,"s deal ) basic sci5tific rese>*2 o!rs are mu* m conc]n$ ) ! eng9e]+ applications ( te*nical k4 ,"s 7 solv$ by c>eful1 logical ?9k+2 o!rs 7 solv$ almo/ by accid5t4 ,"s deal ) a p>ticul> imm$iate task 79 ?is case1 ,project ,tel/>72 o!rs are m conc]n$ ) g5]al plann+ = satellite communications4 ,at ! ,f\ndation3 ,basic ,physical ,pr9ciples ,despite ^! _m important diff]5ces1 !re is "o common ?read runn+ ?r\gh ! solv+ ( all ! problems we h *os54 ,! m5 :o h be5 work+ on !m _h to "k "s basic pr9ciples ( classical physics--pr9ciples t mo/ ( !m fir/ le>n$ 9 _! high s*ool physics classes4 ,y c't1 = example1 calculate a satellite's orbit )\t kn[+ ,newton's ,laws ( ,motion4 ,y c't make optical measurem5ts on a satellite )\t kn[+ ! law ( reflection ( light4 ,y c't decide :at color a satellite %\ld be )\t kn[+ ! law ( heat ex*ange4 ,to emphasize ! importance ( a solid gr\nd+ 9 basic physical pr9ciples1 we h tri$ to h our problems t\* on mo/ ( ! g5]al areas ( physics3 me*anics1 heat1 s\nd1 light1 electricity & magnetism1 electronics1 ! prop]ties ( matt]1 atomic physics1 physics ( ! solid /ate4 ,b mo/ ( !m1 ( c\rse1 are n limit$ to j "o ( ^!--!y cross ! l9es ( a numb] ( areas4 ,= in/ance1 ! problem ( keep+ sol> cell p[] plants work+ 9 space involves laws ( heat1 me*anics1 & atomic physics1 z well z physics ( ! solid /ate4 ,&1 9 /udy+ ! p]ception ( "t delay1 we ev5 bran* out into exp]im5tal psy*ology4 ,problem-,solv+ ,te*niques ,:5 y />t to solve a problem 9 sci5ce or eng9e]+ y c g ab\t x 9 sev]al ways4 ,9 "s cases y h no *oice3 ,!re may be only "o practical me?od ( do+ ! job4 ,o!r times1 !re may be sev]al ways to attack ! problem4 ,y may try "o1 f9d x to be unfruitful1 & !n "w on ano!r approa*4 ,y w see bo? ^! me?ods ( attack 9 ! case hi/ories we pres5t 9 ! next *apt]4 ,"h are "s ( ! te*niques ( sci5tific problem solv+ t we w be discuss+3 --,apply+ basic pr9ciples directly4 ,9 answ]+ ! que/ions 8,h[ d we calculate a satellite's orbit80 & 8,:at color %\ld a satellite be80 ! successful proc$ure 0 to beg9 ) basic kn[n concepts & use !m 9 a new field4 --,adapt+ kn[n devices4 ,to answ] ! "q 8,h[ c we make optical measurem5ts on a satellite80 ! /ory 0 some:at diff]5t3 ,devices t already _h be5 develop$--mirrors1 telescopes1 & ca?ode ray tubes--7 utiliz$ 9 a new & diff]5t way4 --,develop+ entirely new equipm5t4 ,ano!r "q--8,h[ d we keep sol> cell p[] plants work+ 9 space80--deals ) an entirely new area ( inve/igation2 x c\ld only be answ]$ by p]fect+ "s entirely new te*niques4 --,exp]im5tation4 ,sometimes !re is no def9ite answ] to a problem4 ,9 ! case ( 8,w\ld "t delay be a problem 9 us+ a syn*ron\s satellite80 inve/igation is /ill go+ on4 ,our report tells ( "o set ( exp]im5ts t help$ add to our in=mation ab\t ?is problem--! f9al answ]1 if !re is "o1 mu/ come lat]4 ,b1 z ) _m problems1 exp]im5tation cont9ues4 --8,detective "w40 ,our six? problem is really a unique "o--&1 = want ( a bett] way to describe x1 we use ?is title4 ,x tells h[ ! problem ( 8,h[ c we repair an orbit+ satellite80--some?+ nev] ev5 attempt$ be=e--0 +5i\sly solv$ by means ( sci5tific d$uction hundr$s ( miles away f ! problem itself4 ,,case ,,hi/ory ,,no4 #a ,h[ ,d ,we ,calculate a ,satellite's ,orbit8 ,franz ,t4 ,geyl+ ,me*anics ,speciali/--,head1 ,analytic & ,a]ospace ,me*anics ,dep>tm5t ,,! ,,problem ,be=e y c d any?+ ) a communications satellite y h to "k :]e x is at e in/ant ( its motion ar\nd ! e>?4 ,9 o!r words1 y ne$ to "k its orbit q accurately4 ,:5 y "k ?is1 y c pr$ict :5 a p>ticul> /ation on ! gr\nd w be able to see ! satellite & communicate ) x4 ,y also c tell :5 two or m /ations c see ! satellite simultane\sly & communicate ) ea* o!r4 ,& y c e/imate h[ _m satellites w be ne$$ to provide a gr\p ( gr\nd /ations ) en\gh work+ "t to ma9ta9 a communications s]vice4 ,?is la/1 aft] all1 is ! ultimate goal ( all our ef=ts 9 ! communications satellite field4 ,9 det]m9+ a satellite's orbit1 we f9d t we mu/ d ?ree ?+s3 --,we mu/ obta9 in=mation on ! position--& p]haps also ! velocity--( ! satellite :5ev] possible by obs]v+ x ) sci5tific in/rum5ts4 --,we mu/ use ?is in=mation to det]m9e ! satellite's orbit at ! "t ( ! obs]vations4 --,we mu/ be able to tell h[ ?is orbit *anges betwe5 ! times :5 we obs]ve x1 because a satellite's orbit does n rema9 con/ant ) ! passage ( "t4 ,9 ! case ( ! ,e*o ,i satellite 7see page #af71 we engag$ 9 ! fir/ & ?ird ( ^! activities4 ,we _h _m *ances to foll[ ! satellite ) our rad>s1 & we c\ld speculate h[ its orbit 0 *ang+ ?r\gh ! mon?s4 ,9 ! case ( ! ,tel/> ,i satellite1 we engag$ 9 all ?ree k9ds ( activity4 ,we %all take a look at ^! problems 9 ! sequ5ce 9 :i* we came across !m1 = bo? ! ,e*o & ,tel/> satellites4 ,h[ ,we ,track ,satellites ,we collect on ! gr\nd mo/ ( ! in=mation to calculate a satellite's orbit1 us+ optical in/rum5ts or rad> equipm5t4 ,foll[+ a satellite ?r\gh ! sky is call$ track+2 9 ! e>ly days aft] ! fir/ ,sputniks1 "s ( ?is track+ 0 done ) ! nak$ eye or ) v simple telescopes by ! ,moonwat* teams4 ,_m ( y may h obs]v$ ,e*o ,i on a cle> night )\t any k9d ( in/rum5t4 ,illu/ration3 ,figure #a satellite horizon elevation azimu? ,nor? ,ea/ ,if we use a telescope1 we note ! "t ( ! obs]vation & we usually take a photograph ( ! satellite4 ,we locate ! satellite 9 t]ms ( ! two angles %[n 9 ,figure #a4 ,"o ( ^! is ! elevation angle--! numb] ( degrees a telescope mu/ be tilt$ above ! horizon to see ! satellite4 ,! second is ! azimu? angle--! numb] ( degrees betwe5 ! plane 9 :i* we measure ! elevation angle & ! nor? direction4 ,( c\rse1 we c also po9t a rad> ant5na at ! satellite 9 ! same mann]4 ,! rad> c receive a signal transmitt$ by ! satellite1 or else x c s5d a signal to ! satellite & wat* = ! reflect$ waves t ev5tually return4 ,9 ! latt] case1 ! satellite mu/ h suffici5t surface area to produce an adequate reflect$ signal4 ,^! two k9ds ( precision track+ 7 bo? possible ) ,e*o ,i4 ,rad> c also d some?+ t optical equipm5t usually c't d3 measure ! di/ance out to ! satellite4 ,! ,basic ,physics ( ,satellite ,motion ,illu/ration3 ,figure #b e>? nor? pole satellite n t ,! ,e*o ,i satellite 0 laun*$ into a circul> orbit incl9$ at an angle to ! plane ( ! e>?'s equator4 ,9 ,figure #b ?is equatorial plane int]sects ! plane ( ! satellite orbit along ! l9e ,,opm4 ,! po9t ,o repres5ts ! c5t] ( ! e>?1 ! po9t ,m is on ! satellite orbit1 & ! ,po9t ,p is on ! equator4 ,at any in/ant1 ! satellite may be locat$ 9 its orbit by ! angle 1 :i* is measur$ betwe5 ! l9e ,,om & ! l9e ,,oq1 :]e ! po9t ,q is ! satellite's location4 ,if ! satellite moves 9 a circul> orbit1 z 9 ?is case1 ! angle is proportional to "t4 ,t is1 we c write nt4 ,we call n ! angul> spe$ ( ! satellite2 "o way ( measur+ ?is is 9 degrees p] second4 ,?us1 ! satellite is :irl+ at a con/ant spe$ ab\t ! e>? l a /one ti$ to a /r+4 ,let u exam9e ! physics ( ?is situation a little m closely ) ! help ( ,figure #c4 ,if ! satellite is mov+ ) ! velocity v1 !n we "k t ! c5trifugal =ce act+ on x is 7mv7_/7r71 :]e m is ! mass ( ! satellite & r is its di/ance f ! c5t] ( ! e>?4 ,obvi\sly1 no /r+ ties ! satellite to ! e>?1 b ! =ce ( gravitational attraction betwe5 ! e>? & ! satellite has ! same effect4 ,newton's law ( mutual attraction tells u t ?is =ce is proportional to ! product ( ! two masses divid$ by ! squ>e ( ! di/ance betwe5 _! c5t]s1 or 7km7_/7r71 :]e k is a con/ant t ess5tially repres5ts ! mass ( ! e>?4#a ,newton's law also tells u t ?is =ce w be po9t+ t[>d ! c5t] ( ! e>? if ! e>? is sph]ical4 ,:5 ! satellite is 9 circul> motion1 ! c5trifugal =ce & ! gravitational =ce mu/ balance ea* o!r4 ,h5ce we h 7km7_/7r7 7mv7_/7r7 & f ?is we c solve to f9d t ! velocity ( ! satellite mu/ be equal to v 77k7_/7r774 ,9 ! case ( ! ,e*o ,i satellite1 :i* 0 design$ to h a radial di/ance ( r #ejjj miles1 ?is velocity am\nts to ab\t #d4d miles p] second4 ,! "t = "o revolution 9 orbit is obta9$ ) ! =mula ,t 7#br7_/7v74 ,= ! ,e*o satellite ?is "t1 ,t1 turns out to be j ab\t two h\rs4 ,illu/ration3 ,figure #c ,calculat+ ! ,orbit ( ,e*o ,i ,^! basic physical pr9ciples ( satellite motion c give u _m useful answ]s4 ,!y tell u h[ fa/ we mu/ move a precision track] to foll[ ! satellite ?r\gh ! sky1 h[ mu* "t a satellite w sp5d above ! horizon1 & h[ long w be ! "t f "o *ance ( see+ x to ! next4 ,h[ev]1 9 ! ,e*o project we 7 n m]ely conc]n$ ) plann+ our exp]im5ts f h\r to h\r2 we also ne$$ to "k h[ ! satellite w\ld move = weeks & p]haps mon?s 9 advance4 ,:5 y /udy ! motion ( a satellite ov] su* a l5g? ( "t1 y discov] t its circul> orbit w n rema9 ! same z x 0 at laun*4 ,?is fact _h be5 obs]v$ on o!r satellites & 0 to be expect$ also ) ,e*o4 ,9 ev]y?+ we h said s f> x 0 assum$ t ! e>? 0 a p]fect sph]e1 :i* is ! way a geograph]'s globe pres5ts x to u4 ,9 reality1 ! e>? is some:at flatt5$1 ) its diamet] f ! nor? pole to ! s\? pole be+ some:at %ort] ?an its diamet] at ! equator4 ,"o way ( look+ at ?is is to visualize ! e>? z a sph]e ) "s mat]ial add$ 9 ! equatorial zone1 :i* we may call equatorial bulge4 ,?is bulge causes ,e*o's orbit to h a sl[ 8wobble0 ab\t ! e>?'s pol> axis1 some:at l t ( a sp9n+ top4 ,ano!r =ce t makes ! satellite's orbit %ift slightly is ! fa9t pressure caus$ by ! light f ! sun4 ,al?\gh ?is pressure is mu* too small = u to p]ceive )\t ! help ( v delicate in/rum5ts1 x is en\gh to affect a satellite1 :i* has no?+ to support x 9 space & is expos$ to sol> pressure = a v long "t4 ,s9ce ! ,e*o balloon is a pla/ic sph]e1 #ajj feet 9 diamet]1 t weighs only a little m ?an #ajj p\nds1 ! light rays /rik+ its surface are en\gh to cause a second 8wobble0 effect4 ,?is wobble c5t]s ab\t ! l9e f ! e>? to ! sun4 ,light pressure also =ces ! orbit to g slightly out ( r\nd f a p]fect circle1 & o!r gradual effects on ! satellite's orbit are caus$ by ! gravitational attraction ( ! moon & ! sun4 ,all ^! di/urbances are ev]-pres5t & act simultane\sly1 & a satellite's total response to !m is v complicat$4 ,=tunately1 h[ev]1 mo/ ( ! *anges take place at a v sl[ & uni=m rate1 & we c pr$ict !m fairly accurately4 ,calculat+ ! ,orbit ( ,tel/> ,i ,illu/ration3 ,figure #d ,9 ,project ,tel/> we _h to calculate ! satellite's orbit f obs]vations made by our precision track]s4 ,?is introduc$ a few problems 9 addition to ! ones we enc\nt]$ ) ,project ,e*o4 ,9 ! fir/ place1 ! orbit ( ! ,tel/> satellite is a elongat$ ellipse1 z indicat$ 9 ,figure #d1 r ?an be+ almo/ circul>1 z 9 ! case ( ,e*o ,i4 ,we m5tion$ e>li] t a precision track] c furni% data on a satellite's elevation angle1 ,e1 & azimu?1 ,a 7see ,figure #a74 ,x c also give u a read+ = 1 ! di/ance f ! track] to ! satellite 7,figure #d74 ,if we "k ! position ( ! track] on ! e>?1 we c r$uce ! quantities ,a1 ,e1 & to ! angle & ! di/ance r 7measur$ f ! c5t] ( ! e>? to ! satellite74 ,^! two quantities locate ! satellite 9 ! plane ( its orbit1 b 9 ord] to describe its position completely we mu/ also specify ?is orbital plane4 ,9 ,figure #e ! orbital plane is %[n z a %ad$ surface1 ) & r be+ ! same z be=e4 ,y w recall t ! l9e ,,om repres5ts ! int]section betwe5 ?is plane & ! equatorial plane2 we call ! angle i betwe5 ! two planes ! incl9ation ( ! orbit4 ,f9ally1 we h ! angle betwe5 ! l9e ,,om & "s l9e ,,oa to ! po9t ,a1 :i* we c *oose z any conv5i5t spot 9 ! equatorial plane4 ,n[ we h specifi$ ! orbital plane completely4 ,! po9t ,a c be f\nd f day to day by fix+ its position relative to a c]ta9 /> 9 ! sky4 ,illu/ration3 ,figure #e ,figures #d & #e tell u some?+ ab\t ! geometry ( ! satellite's position 9 space1 b = ! complete /ory we mu/ also give ! "t at :i* x c be f\nd !re4 ,= ?is purpose1 !re are "s a/ronomical laws t relate position on an elliptic orbit to "t4 ,two ( ^! are illu/rat$ 9 ,figure #f2 9 look+ at ?is figure1 y %\ld imag9e t y are /&+ (f to "o side ( ! orbital plane to get a good view ( ! entire orbit4 ,! longe/ dim5sion ( ! ellipse1 #b;a1 is call$ ! major axis2 ?is dim5sion is relat$ to ! satellite's p]iod--! "t x takes to g once ar\nd ! ellipse4 ,m ?an ?ree hundr$ ye>s ago ! a/ronom] ,johannes ,kepl] obs]v$ t ! p]iod ,t1 ( an ellipse is ,t #b77;a7_/7k771 :]e k aga9 0 7us+ ,newton's "w7 ess5tially ! mass ( ! e>?4 ,illu/ration3 ,figure #f ,in/ead ( a complete revolution1 we may only be conc]n$ ) "p ( "o orbit4 ,let's say t ?is "p lies betwe5 ! two positions ,p & ,p t ! satellite occupies at ! two times t & t 7see ,figure #f74 ,!n ano!r ( ,kepl]'s laws says t ! ratio betwe5 ! "t diff]5ce t - t & ! p]iod ,t equals ! ratio betwe5 ! sector ( ! ellipse ,,op,p & ! area ( ! entire ellipse4 ,n[ let u see h[ we c use ! quantities r1 1 i1 & z well z ,kepl]'s two "t laws to det]m9e ! motion ( ! satellite 9 space4 ,suppose t we h made obs]vations ( ! ,tel/> at two times t & t & t we h measur$ its di/ance along l9es & 9 ,figure #g4 ,9 o!r words1 we "k t at ^! two times ! satellite 0 at ! po9ts ,p & ,p4 ,s9ce ?ree po9ts det]m9e a plane1 we "k 9 ?is case t ,p1 ,p1 & ,o def9e ! satellite orbital plane4 ,kn[+ ?is1 we c n[ calculate ! angles & 1 ! di/ances r & r1 & ! angles i & 4 7,! detail$ =mulas = ?is are d]iv$ f analytic geometry47 ,illu/ration3 ,figure #g ,h[ev]1 we /ill d n "k ! l5g? & ! wid? ( ! p>ticul> ellipse ! satellite is foll[+ & h[ ?is orbit is ori5t$ )9 ! orbital plane4 ,let u imag9e aga9 t we c /& (f to "o side ( ! orbit & take a good look at x2 ,figure #h %[s u :at we w\ld see4 ,!re are ! two po9ts ,p & ,p at :i* we h obs]v$ ! satellite4 ,we "k ! positions ( ^! po9ts relative to ea* o!r & 9 relation to ! c5t] ( ! e>?1 because we h already calculat$ r1 r1 1 & 1 ,b any numb] ( ellipses c\ld be made to pass ?r\gh ^! two po9ts4 ,"s might be v l>ge1 o!rs might be s n>r[ t !y w\ld int]sect ! e>? & ?us be impossible4 ,h[ev]1 only "o ( ^! ellipses w satisfy ! "t diff]5ce t we obs]v$ betwe5 ,p & ,p4 ,9 o!r words1 ! %ape & p]iod ( ?is p>ticul> ellipse mu/ be su* t x w cause ! satellite to pass ?r\gh ,p & ,p 9 exactly ! "t int]val t - t4 ,if we "w out our "t =mulas1 we w conv9ce ourselves t !re is only "o su* ellipse4 ,:5 we h f\nd x1 we h det]m9$ ! orbit ( ! ,tel/> satellite f ! two obs]v$ positions & times4 ,illu/ration3 ,figure #h ,illu/ration3 ,figure #i ,9 pr9ciple !n1 we c\ld keep track ( ! ,tel/> satellite by mak+ a pair ( obs]vations ,p & ,p1 & !n pr$ict+ ahead a %ort segm5t ( an orbit t is ! ellipse we h comput$4 ,aft] a :ile we mu/ v]ify ?is ellipse ) two m obs]vations ,p & ,p1 pr$ict ahead ov] ano!r segm5t1 & v]ify aga9 ) ,p & ,p 7see ,figure #i71 ,! reason we h to keep tak+ new measurem5ts is t ! elliptic orbit does n rema9 ! same4 ,z we discuss$ 9 connection ) ,e*o ,i1 ! orbital plane w 8wobble0 ab\t ! e>? because ( ! equatorial bulge4 ,we also "k t ! orbit's major axis w revolve )9 ! orbital plane4 ,z we h se5 be=e1 ^! effects are small & c be repres5t$ by appropriate ma!matical =mulas4 ,if we calculate !m1 we w see ! connection betwe5 "o pair ( obs]vations & a lat] "o1 & ev5tually we c increase ! "t int]val betwe5 successive pairs ( obs]vations4 ,!re are also ma!matical =mulas t we c use to pr$ict ! position ( ! satellite = _m revolutions 9 its elliptic orbit4 ,9 ord] to pr$ict orbits successfully1 we mu/ also realize t ! measurem5ts we obta9 f a precision track]1 su* z ! angles ,a & ,e & ! di/ance 1 are always subject to small inaccuracies4 ,?us x is n really possible to take j two measurem5ts l ,p & ,p & det]m9e a satisfactory orbit f !m4 ,9 reality1 our track] takes _m read+s1 & ^! are av]ag$ to give adequate in=mation ab\t ! orbit4 ,!re=e1 ! picture we h 9 m9d is n q l ,figure #g1 b r l ,figure #aj4 ,"h ! track]s h e/abli%$ a s]ies ( po9ts t are some:at scatt]$1 & by tak+ av]ages we c calculate an orbit t passes ?r\gh !m 9 a smoo? fa%ion4 ,! track]s we h m5tion$ s f> h giv5 u azimu? & elevation angles & also ! di/ance to ! satellite at e in/ant4 ,sometimes we mu/ use simpl] in/rum5ts t d n yield all ?is in=mation4 ,!y might1 = in/ance1 only give u ! two angles4 ,! ma!matics ( calculat+ an orbit f su* measurem5ts is some:at diff]5t1 b ! process is fundam5tally ! same z we h discuss$ "h4 ,:5 y d ^! calculations = ! ,tel/> satellite f "o day to ! next--& especially if y h m ?an "o satellite to keep track (--! am\nt ( "w w become q l>ge4 ,n[adays our calculations are done = u on electronic comput]s1 :i* bo? receive in=mation f ! track+ in/rum5ts automatically ?r\gh ,teletype or ,data,phone *annels & s5d back in=mation conc]n+ future positions ( ! satellite to ! gr\nd /ations4 ,!re are /ill q a few problems to be solv$1 & we are pres5tly work+ on ways ( mak+ all ?is equipm5t p]=m ! orbit pr$ictions = ! ,tel/> satellites automatically & effici5tly4 ,illu/ration3 ,figure #aj ,franz ,t4 ,geyl+ 0 born 9 ,ti5ts91 ,*9a1 & receiv$ a ,b4,s4 9 #aiej1 an ,m4,s4 9 #aiea1 & a ,ph4,d4 9 #aied f ,/an=d ,univ]sity4 ,he jo9$ ,bell ,telephone ,laboratories 9 #aied1 & has be5 engag$ 9 cele/ial me*anics /udies ( rockets & satellites1 z well z /ress analysis ( subm>9e cables4 ,,case ,,hi/ory ,,no4 #b ,:at ,color ,%\ld a ,satellite ,be8 ,pet] ,hrycak ,me*anical ,eng9e]--,memb] ( ,/aff1 ,electron ,device ,laboratory ,,! ,,problem ,x is important = a satellite to /ay at ! prop] temp]ature :ile x is orbit+ 9 space4 ,! in/rum5ts abo>d x mu/ cont9ue to op]ate prop]ly1 & "o way ( insur+ ?is is to keep !m f be+ expos$ to extreme heat or cold4 ,we c1 ( c\rse1 regulate a satellite's temp]ature some:at ) v>i\s k9ds ( devices1 & we c see t "o ( its ends does n po9t t[>ds ! sun = too long4 ,b 9 design+ ! ,tel/> satellite we also want$ to control temp]ature 9 an easi] way3 by cov]+ ! satellite's ext]nal surface ) mat]ial ) ! be/ prop]ties--includ+ ! "r color--= ma9ta9+ its ov]-all temp]ature at ! "r level4 ,! ,radiation ( ,heat ,a satellite's temp]ature is det]m9$ by ! balance betwe5 ! heat t ent]s ! satellite & ! heat t leaves x4 ,?is means t we mu/ be conc]n$ ) h[ heat is transf]r$4 ,heat c be transf]r$ 9 ?ree ways3 by conduction1 :5 two bodies are 9 direct contact & _! molecules collide2 by convection1 :i* utilizes ! movem5t ( w>m curr5ts 9 a fluid2 & by radiation1 9 :i* heat en]gy travels z electromagnetic waves at ! spe$ ( light4 ,) a satellite1 we are conc]n$ only ) ! la/ ( ^!1 s9ce ! only way en]gy c be ga9$ or lo/ 9 space is by radiation4 ,9 ! transf] ( heat by radiation1 ! surface ( ! heat$ body--su* z a satellite--is v important4 ,all en]gy ga9$ mu/ be absorb$ at ! surface2 all en]gy leav+ mu/ be emitt$ at ! surface4 ,s ! physical prop]ties ( ?is surface control h[ en]gy is absorb$ & h[ x is emitt$4 ,! orig9 ( ! radiant en]gy is vitally important2 mo/ surfaces1 = in/ance1 w behave diff]5tly :5 expos$ to sol> radiation f ! sun's temp]ature ( #aj1jjj ,fahr5heit ?an :5 expos$ to radiation f ne>by objects at room temp]ature4 ,absorptivity & ,emissivity ,! physical prop]ty ( a mat]ial t controls ! way x absorbs radiant en]gy is call$ its absorptivity1 & ! prop]ty t controls its emission ( en]gy is its emissivity4 ,= absorptivity we use ! symbol 2 = emissivity we use ! symbol 4 ,:5 radiant en]gy rea*es a surface1 only a c]ta9 "p ( x is absorb$2 ! re/ is ei!r reflect$1 j z light rays are reflect$1 or else passes "r ?r\gh x4 ,! absorptivity1 1 ( a sub/ance tells u :at p]c5tage ( radiant en]gy x w absorb4 ,a p]fect absorb]1 or black body1 w\ld absorb all ! radiant en]gy t rea*$ x4 ,if su* an ideal sub/ance exi/$ 7:i* x doesn't7 we w\ld say x _h an ( #a4 ,! actual absorptivities ( real sub/ances are indicat$ by numb]s betwe5 #j & #a3 ,! ( black velvet clo?1 = example1 is ab\t #j4ig2 t ( a poli%$ silv] mirror is ab\t #j4jh = sol> radiation 7absorptivity = mo/ poli%$ metals = room temp]ature radiation is ev5 l[]74 ,we measure emissivity1 1 9 v mu* ! same way4 ,a hypo!tical black body w\ld emit all ! en]gy x possibly c\ld & h an ( #a2 ! emissivities ( real sub/ances are indicat$ by numb]s betwe5 #j & #a4 ,= any giv5 frequ5cy 7or color7 ( light1 a sub/ance's absorptivity & emissivity are equal2 h[ev]1 ! total spectrum ( frequ5cies ( ! en]gy absorb$ is usually diff]5t f t ( ! en]gy emitt$4 ,! ratio betwe5 emissivity & absorptivity1 _/1 is v important1 z we %all see lat]4 ,if ?is ratio is great] ?an #a1 x means t a sub/ance absorbs heat fa/] ?an x emits x1 & ?us t5ds to become w>m]4 ,if ! ratio is less ?an #a1 ! rev]se is true--! surface emits radiant en]gy at a fa/] rate ?an x absorbs x1 & t5ds to become cool]4 ,h[ ,we ,measure ! ,radiation ( ,heat ,?is is "o ( ! fundam5tal relation%ips ( mod]n physics3 ,qbody ,a,t4 ,x 0 discov]$ exp]im5tally by ,josef ,/efan 9 #ahgi1 & v]ifi$ !oretically by ,ludwig ,boltzmann2 x is kn[n z ! ,/efan-,boltzmann ,law4 ,?is =mula tells u ! am\nt ( radiant en]gy1 ,qbody1 t w be emitt$ by a body hav+ ! surface area ,a :5 x is at ! temp]ature ,t4 ,temp]ature1 "h1 is measur$ 9 degrees ,rank9e 7,r71 or ,fahr5heit temp]ature above absolute z]o 7to calculate degrees ,rank9e1 add #dfj to ! temp]ature 9 degrees ,fahr5heit74 ,! expression ,a is us$ to %[ t only a c]ta9 fraction ( ! en]gy t w\ld leave a p]fect black body ( area ,a w actually leave a real body ( ! same size2 ! size ( ?is fraction is det]m9$ by ! body's emissivity4 ,! symbol is a quantity we call ! ,/efan-,boltzmann con/ant4 ,we c also calculate ! heat f ! sun t w be absorb$ by a body4 ,if we let ,s be ! total am\nt ( sol> en]gy t w\ld be absorb$ by a p]fect black body1 ,s w be ! am\nt t is actually absorb$ by a body ) an absorptivity ( = sol> radiation4 ,if our body is a sph]ical satellite1 ! sun's rays w only /rike x f a s+le direction4 ,?us only an area equival5t to ! sph]e's cross-section 7l>ge/ inscrib$ circle7 w receive en]gy at any "o "t4 ,s9ce1 z %[n 9 ! sket*1 ?is area 7a r7 is "o-f\r? t ( ! sph]e's total surface area 7,a #dr71 we "k t ! radiant en]gy f ! sun t is absorb$ w be ,qsun 7,a7_/7#d7,s4 ,a man-made satellite's position relative to ! e>? is v l t ( ! e>? 9 relation to ! sun2 ! e>?1 aft] all1 is itself a satellite ( ! sun4 ,& dur+ mo/ ( its useful life a satellite w be 9 !rmal equilibrium--x w be los+ j z mu* heat en]gy by its own radiation into space z x w be ga9+ f o!r s\rces1 prim>ily ! sun4 ,s9ce ! total am\nt ( en]gy x absorbs is equal to ! am\nt ( en]gy x emits1 ,qbody is equal to ,qsun4 ,?is means t we h ! equality ,a,t 7,a7_/7#d7,s4 ,n[1 if we solve ?is = temp]ature1 we w get ,t 777_/77 7,s7_/7#d77774 ,illu/ration3 ,al?\gh ! total surface area1 ,a1 ( a sph]e is #dr1 light rays f ! sun only /rike half ! surface at any "o "t4 ,?is area1 a1 is effectively equal to ! sph]e's cross-section1 r4 ,?is equation is well kn[n 9 a/ronomy1 & has be5 us$ = m ?an #hj ye>s to calculate ! temp]atures ( v>i\s objects 9 ! sky4 ,today1 we /ill f9d x useful = measur+ ! surface temp]atures ( man-made satellites su* z ,tel/>4 ,s9ce bo? ,s & are kn[n con/ants 79 ?is case1 we use ! quantities ,s #dde & #j4agc #aj71 y c see t temp]ature is dep5d5t on ! _/ ratio4 ,f9d+ ! ,"r ,surface = ,tel/> ,illu/ration3 ,cutaway view ( ! inside ( ! ,tel/> ,i satellite1 %[+ ! electronics cani/] cov]$ ) its protective blanket ( _m lay]s ( ,myl>4 ,to control temp]ature1 %utt]s automatically op5 all ! way if ! cani/] gets hott] ?an #hj;,f1 close completely if x goes d[n to #ej;,f4 %utt] 7clos$7 electrical heat transf] insulation blanket heat transf] by radiation %utt] 7op57 sol> cells electronic *assis heat transf] by circulation !rmal control me*anism nylon lac+ micr[ave ant5nas frame ,9 design+ ! ,tel/> satellite1 bo? its int]nal & ext]nal temp]atures _h to be controll$4 ,! electronics cani/] inside ! satellite op]ates be/ if x /ays at approximately room temp]ature ( #fe to #ge;,f4 ,?is mu* heat is suppli$ 9 ! cani/] by dissipation ( electrical en]gy f ! sol> cells4 ,! conta9] is well insulat$ to keep its temp]ature relatively /able1 & x has %utt]s t op5 automatically if x beg9s to get ov]heat$ 7see above74 ,! op]at+ *>act]i/ics ( ! sol> cells on ,tel/>'s surface also _h to be consid]$2 !y "w bett] at r cool temp]atures4 ,s we decid$ to keep ! satellite's sk9 at an av]age temp]ature ( ab\t #j;,f1 al?\gh temp]atures actually w range q a bit above & bel[ ! av]age z ! satellite moves f sun to %ad[4 ,n[1 us+ ?is av]age temp]ature ( #j;,f 7conv]t$ to #dfj,r7 z ,t 9 our =mula1 we c solve = _/4 ,we f9d t ?is gives u a ratio ( approximately #j4g = ! satellite's surface4 ,h[ev]1 ?is pres5ts a problem4 ,almo/ #dj p] c5t ( ,tel/>'s surface is tak5 up by its p[] plant ( #cfjj sapphire-cov]$ sol> cells4 ,^! cells1 un=tunately1 h a relatively high _/ ratio--_! is #j4h & _! is #j4ed1 = an _/ ( #a4e4 ,?is means t ! portion ( ! surface n us$ by ei!r sol> cells or ant5na op5+s mu/1 9 ord] to give u an ov]-all av]age ( ab\t #j4g1 h a v l[ _/ ratio--less ?an #j4c4 ,to get ?is sort ( ratio1 we _h to select c>efully ! mat]ial = ! out] surface ( ! ,tel/> satellite4 ,!re 7 _m k9ds ( surfaces t might h be5 us$2 !y c\ld h be5 metal or non-metal1 r\gh or smoo?1 %9y or dull4 ,& !y c\ld h be5 any color f black to :ite4 ,h[ev]1 to get a #j4c ratio we ne$$ some?+ ) a relatively high emissivity = ! l[-frequ5cy electromagnetic radiation t ! satellite emits & a r l[ absorptivity = ! high-frequ5cy radiation com+ f ! sun4 ,high emissivity meant t we %\ld use a nonmetal surface r ?an poli%$ metal1 s9ce ! emissivity ( nonmetals is q high at ! temp]atures 9 :i* we 7 int]e/$1 :ile t ( poli%$ metals is relatively l[4 ,&1 to get l[ absorptivity1 we decid$ t ! color ( ^! surface areas %\ld be v close to a pure :ite4 ,illu/ration3 ,p>tially molt5 alum9um oxide p>ticles be+ spray$ onto alum9um out] surface panels4 ,!re 7 sev]al sub/ances t met our requirem5ts4 ,aft] te/+ a numb] ( !m1 we decid$ to use alum9um panels coat$ ) a ?9 lay] ( alum9um oxide 7,al,o74 ,?is coat+ is v pure1 h>d1 & /able1 & we left x r\gh to m9imize *anges due to meteoroid abrasion4 ,its _/ ratio is #j4bd4 ,! alum9um oxide coat+ c be appli$ by means ( ! plasma jet process--p>ticles ( alum9um oxide are heat$ to a p>tially molt5 /ate1 mix$ ) gases1 & !n spray$ onto ! clean$1 pre-coat$ alum9um panels 7see illu/ration above74 ,us+ ?is c>efully select$ out] surface has help$ solve ! temp]ature-control problem4 ,s9ce ,tel/> has be5 9 orbit its int]nal & sk9 temp]atures h kept well )9 ! ranges we want$ !m to4 ,?us y c see h[ "s basic =mulas f classical physics help$ u *oose ! "r mat]ial = ! satellite's surface--& ev5 :at color x %\ld be4 ,! blue-&-:ite *eck]$ appe>ance t ,tel/> ,i f9ally took on 0 no accid5t--x 0 ! result ( c>efully comb9+ v>i\s colors & mat]ials 9 j ! "r am\nts to obta9 ! temp]ature balance we ne$$4 ,pet] ,hrycak 0 born 9 ,przemysl1 ,we/]n ,ukra9e1 & receiv$ a ,b4,s4 9 #aied1 an ,m4,s4 9 #aiee1 & a ,ph4,d4 9 #aifj f ! ,univ]sity ( ,m9nesota4 ,he jo9$ ,bell ,telephone ,laboratories 9 #aifj1 & has work$ on l[ temp]ature refrig]ation problems & !rmal design & !rmal te/+ ( ! ,tel/> satellite4 ,,case ,,hi/ory ,,no4 #c ,h[ ,c ,we ,make ,optical ,measurem5ts on a ,satellite8 ,je(ry ,s4 ,c\rtney-,pratt ,physici/--,head1 ,me*anics ,rese>* ,dep>tm5t ,,! ,,problem ,s9ce ! fir/ ,tel/> satellite w5t into orbit1 we h tri$ to trace its pa? ?r\gh space precisely4 ,b we also h _h to keep a con/ant *eck on ! position1 or attitude1 t ! satellite takes z x travels4 ,we are p>ticul>ly int]e/$ 9 ! direction ( ! sp9 axis ab\t :i* x revolves1 & we also want to "k its sp9 rate1 :i* is ! numb] revolutions ! satellite makes ea* m9ute4 ,al?\gh ^! might seem relatively simple jobs1 !y actually turn$ out to be r complicat$4 ,& only at virtually ! la/ m9ute1 j be=e ! satellite's design 0 f9ally set1 did we ?9k ( a new way ( us+ reflect$ fla%es ( sunlight to report on its sp9 axis & sp9 rate4 ,:y ,we ,want to ,"k ,ab\t ! ,sp9 ,axis ,:5 ! satellite 0 inject$ into its orbit1 x 0 sp9-/abiliz$ to keep x f tumbl+ ov] & ov]1 mu* z a rifle bullet is /abiliz$ by be+ spun ab\t its longitud9al axis4 ,! ,tel/> satellite is r\ghly sph]ical1 & x 0 design$ to sp9 ) ! helical ant5na end z its nor? pole & ! ant5na b&s z its equator4 ,on ,july #aj1 #aifb1 ! satellite 0 giv5 an initial sp9 ( #agg4g revolutions a m9ute4 ,z we expect$1 ?is rate is decreas+ gradually2 aft] two ye>s x w only be sp9n+ "o t5? z fa/4 ,! mo/ important reason = keep+ a close wat* on ! satellite's sp9 axis is to make sure t micr[ave signals are s5t & receiv$ /eadily4 ,x isn't possible to build an ant5na t radiates at exactly ! same p[] 9 all directions4 ,tel/>'s ant5nas "w v well1 b !y op]ate bett] 9 ! direction ( ! satellite's equator ?an !y d t[>ds its poles4 ,?is means t if ! sp9 axis is con/antly *ang+ transmission w fade 9 & out--ev5 at times pass+ ?r\gh 8null0 :]e no transmission at all is possible4 ,no s+le fix$ ori5tation is p]fect = ! sp9 axis1 b we decid$ t ! be/ av]age position w\ld be to keep x always p]p5dicul> to ! plane ( ! e>?'s orbit4 ,we tri$ to make sure t ! sp9 axis w\ld n v>y by m ?an five degrees f ?is direction at any "t--al?\gh x probably c\ld dep>t z mu* z #ae or #bj degrees )\t do+ s]i\s h>m4 ,a second reason = be+ c>eful ab\t ! satellite's sp9 axis is ! problem ( heat balance4 ,if "o end ( ! satellite po9ts con/antly at ! sun & ! o!r end does n1 ! end ne> ! sun w get mu* too hot & ! o!r w get mu* too cold4 ,!re=e1 we tri$ to fix ! sp9 axis s t x /ay$ p]p5dicul> to a l9e drawn f ! satellite to ! sun4 ,we also want$ to get a cont9u+ report on ! effects ( ! magnetic field ( ! e>? at high altitudes4 ,we knew ^! w\ld cause ! sp9 axis to *ange ) "t1 or precess1 b we c\ldn't be exactly sure :at ^! *anges w\ld be4 ,s9ce ! ori5tation ( ,tel/>'s sp9 axis 0 s important we in/all$ a torque coil 9 ! satellite4 ,?is is a coil ( wire 9 :i*1 ^u a signal f ! gr\nd1 an electric curr5t c be made to fl[4 ,! curr5t produces a magnetic field t int]acts ) ! e>?'s magnetic field to *ange ! position ( ! satellite's sp9 axis4 ,h[ev]1 we c\ld n be sure t ?is device w\ld "w prop]ly--& ?is is ano!r reason :y we want$ to keep track ( ! exact position ( ! sp9 axis4 ,ways ( ,measur+ ! ,sp9 ,axis ,"o ( ! devices built into ,tel/> is a set ( six sol> aspect cells spac$ at regul> int]vals ar\nd ! satellite4 ,^! give a fairly accurate indication ( ! angle betwe5 ! sp9 axis ( ! satellite & a l9e jo9+ ! satellite & ! sun4 ,:5 sunlight /rikes ^! sol> cells1 !y produce electric curr5ts1 & ! value ( ! curr5t f ea* cell is s5t back to ! gr\nd via telemetry4 ,?ree ( ! cells are 9 ! satellite's nor!rn hemisph]e2 ?ree are 9 ! s\!rn hemisph]e4 ,if ,tel/>'s nor? pole 7 po9t+ to ! sun1 = example1 ! ?ree nor!rn cells w\ld record l>ge1 equal curr5ts2 ^? 9 ! s\!rn hemisph]e w\ld %[ z]o curr5t4 ,b if ! sp9 axis 7 p]p5dicul> to ! satellite-sun l9e 7z we want x to be7 all six cells w\ld report equal1 av]age-siz$ curr5ts1 :i* w\ld fluctuate z ! satellite spun ar\nd4 ,! sol> cells 7 c>efully calibrat$ be=e ,tel/> 0 laun*$1 & we e/imate t !y c tell u ! angle betwe5 ! satellite's sp9 axis & ! satellite-sun l9e to )9 "o or two degrees4 ,h[ev]1 ?is "o angle is n en\gh to locate ! sp9 axis exactly4 ,z y c see 9 ,diagram #a1 !re are _m possible positions = ! sp9 axis ,,op t h ! same angle ) ! satellite-sun l9e ,,os4 ,^! positions all w\ld lie on ! surface ( an imag9>y cone ,,opp t has ,,os z its axis & #b z its v]tex angle4 ,we ne$ to h a second measurem5t to f9d a s+le position = ! sp9 axis4 ,z late z ,novemb] #aifa we _h n f\nd a satisfactory way to make su* a second measurem5t4 ,!n ,donald ,gibble ( ,bell ,telephone ,laboratories sugge/$ t we obs]ve ! reflections ( sunlight f mirrors fitt$ onto ! satellite#b4 ,only :5 a satellite is 9 ! "r position c y see ! reflection ( sunlight f a plane surface on its body4 ,diagram #b %[s h[ fla%es ( reflect$ light are obs]v$4 ,! light ( ! sun1 ,s1 is reflect$ f a plane surface1 ,r1 on ! satellite to our obs]v+ /ation1 ,t1 on ! e>?4 ,if we imag9e ! l9e ,,orb drawn p]p5dicul> to ,r1 we "k1 f ! law ( reflection1 t ! angle ( incid5ce1 i1 made by ! sunlight to ?is l9e w be equal to ! angle ( reflection1 i1 betwe5 ! reflect$ light & ! same l9e4 ,! law ( reflection also tells u t ! sun1 ! l9e ,,orb1 & ! obs]v+ /ation all mu/ n[ lie 9 ! same plane4 ,&1 s9ce we c calculate :]e ! satellite is 9 its orbit at ?is exact mom5t1 we c locate l9e ,,orb4 ,b :at ab\t ! sp9 axis8 ,we "k :]e on ! satellite our reflector ,r is locat$1 s we "k ahead ( "t :at ! angle betwe5 ,,orb & ! sp9 axis1 ,,op1 w be4 ,we call x ! fla% angle4 ,?us we c tell t ! sp9 axis w be some:]e on ! surface ( an imag9>y cone ,,opp t has ,,orb z its axis & #b z its v]tex angle#c4 ,illu/ration3 #a4 ,sol> aspect cells on ! satellite report via telemetry ! am\nt ( sunlight !y receive2 f ^! data we c calculate ! angle betwe5 ! satellite's sp9 axis1 ,,op1 & ! satellite-sun l9e1 ,,os4 ,?is means t ,,op c be any:]e on ! surface ( cone ,,opp4 ,illu/ration3 #b4 ,:5 sunlight is reflect$ to obs]v+ /ation ,t on ! e>?1 we "k t ! angle ( incid5ce i mu/ be equal to ! angle ( reflection i1 &1 if ,,orb is a l9e p]p5dicul> to ! reflector ,r1 we "k t ! sun1 ! obs]v]1 & l9e ,,orb mu/ all lie 9 "o plane4 ,s9ce we also "k ! position ( ! satellite 9 its orbit & ! di/ance f x to ! e>?1 we c locate l9e ,,orb precisely4 ,! reflector ,r is set at an angle ( #fh f ! sp9 axis ,,op4 ,?is tells u t ! sp9 axis mu/ lie on ! cone ,,opp1 :i* is n[ precisely det]m9$ by its axis ,,orb & its v]tex angle #b1 equal to #acf4 ,illu/ration3 #c4 ,cones ,,opp & ,,opp int]sect along ! two l9es ,,op & ,,oq1 s ^! are ! only possible sp9 axis locations4 ,f our g5]al k ( ! situation 7or f any ?ird measurem5t ( gl9t "t71 ,,oq c be rul$ out1 & we conclude t only ,,op c be ! true sp9 axis4 ,9 ,diagram #c we h comb9$ our two measurem5ts ( ! satellite's sp9 axis4 ,y c see t ! two cones w int]sect along two /raight l9es1 ,,op & ,,oq2 ^! are ?us ! only possible positions t w satisfy bo? our measurem5ts4 ,actually1 ( c\rse1 only "o ( ^! l9es is ! true location ( ! sp9 axis4 ,& x is usually obvi\s :i* "o x is1 :5 we consid] all our o!r data ab\t ! satellite's position4 ,us+ ?is te*nique1 if we measure ! exact times :5 we see fla%es ( reflect$ sunlight f ,tel/>1 we c comb9e t in=mation ) data f our six sol> aspect cells & get a good plot ( ! position ( ! satellite's sp9 axis4 ,9 !ory1 ?is look$ l a v promis+ idea4 ,b f9d+ a satisfactory way to put x into practice 0 some?+ else aga94 ,our fir/ ?\ght 0 simply to make use ( ! light reflect$ f ! sapphire cov]s on ! satellite's sol> cells4 ,h[ev]1 ^! cov]s h a l[ coeffici5t ( reflection & d n =m a completely flat surface4 ,?is means t ! light reflect$ f !m is v mu* r$uc$ 9 int5sity & spreads out too mu* to give u ! precise read+s we want4 ,on ! o!r h&1 if we atta*$ a plane mirror ) a high reflection coeffici5t to ! satellite1 we ?\ght we c\ld pick up ! m9ute fla%es ( reflect$ light f a di/ance ( z mu* z a few ?\s& miles4 ,s we decid$ to press ahead ) ?is s*eme & in/all "o or m reflectors on ! satellite4 ,by ! "t we />t$ "w on ! mirrors1 ! f9al design ( ,tel/> ,i 0 almo/ complete2 ?is meant t we _h to squeeze our mirrors abo>d x z be/ we c\ld4 ,! mo/ /r+5t physical requirem5t 9 design+ !m 0 weight2 !y c\ld n add m ?an half a p\nd to ,tel/>'s total load4 ,nor c\ld !y project m ?an "o-eigh? in* f ! satellite's surface1 or !y might int]f]e ) ! radiation patt]n = ! ma9 ant5na4 ,we also decid$ to make ! mirrors out ( highly poli%$ metal1 s9ce any o!r possible mat]ial might break too easily4 ,& ! mirrors _h to be z flat z possible1 s ! beam ( reflect$ sunlight w\ld n div]ge by m ?an "o degree4 ,?us we _h to design mirrors t w\ld be v ?91 v %9y1 v flat1 v light1 & almo/ unbreakable4 ,aft] mu* exp]im5t+1 we solv$ ?is r tricky problem4 ,! mirrors we add$ onto ,tel/> ,i1 z y c see 9 ! illu/ration bel[1 7 ma*9$ f alum9um alloy %eet1 c>efully poli%$ by h& ) abrasive pap]s1 & buff$ on a clo? :eel4 ,f9ally1 we evaporat$ a ?9 lay] ( pure alum9um onto _! surfaces to improve _! reflection coeffici5ts & make !m resi/ant to corrosion4 ,! ?ree mirrors 7 fa/5$ to ! surface ( ! satellite ) small screws1 :i* _h to be tight5$ & %imm$ v c>efully s t ! mirrors /ay$ z flat z possible4 ,locat+ ! ,mirrors on ! ,satellite ,z we m5tion$ above1 ! fla% angle betwe5 ! satellite's sp9 axis & a l9e p]p5dicul> to ! mirror is v important 9 our calculations4 ,we made detail$ /udies ( ! v>i\s fla% angles t w\ld be possible dur+ ! fir/ #fj days aft] laun*4 ,we plott$ ! times :5 ! satellite w\ld be above ! horizon :ile our ,craw=d's ,hill1 ,new ,j]sey1 obs]v+ /ation 0 9 d>kness1 & we made all[ance = satellite orbits t might deviate slightly f ! plann$ "o4 ,^! calculations told u t ! be/ fla% angle = ! mirror w\ld be #fh degrees--:i* is ! angle made by ! fir/ facets above ,tel/>'s equatorial ant5na b&4 ,s we locat$ a flat mirror on "o ( ^! facets4 ,because "o ( ! sol> aspect cells 0 already in/all$ 9 ! c5t] ( ?is facet1 we 7 =c$ to cut a circul> hole out ( ! c5t] ( ! mirror4 ,b we knew t "o mirror c\ld n d ! :ole job4 ,aft] ,tel/> ,i _h be5 9 orbit m ?an #cj days1 ! #fh-;degree mirror w\ld only be 9 position to give infrequ5t fla%es1 & "o at ab\t #ie degrees w\ld be m useful4 ,?is pres5t$ two problems4 ,fir/1 no facet on ! satellite makes a #ie-;degree angle ) ! sp9 axis4 ,h[ev]1 we c\ld use "o ( ! facets j bel[ ! equatorial ant5na1 :i* makes a #aab-;degree angle1 & groove or facet ! mirror s t its reflect+ faces became n>r[ /rips slant$ #ag degrees away f ! base at ! angle ( #ie degrees 7#aab - #ag #ie74 ,our second problem 0 space--s9ce !re 0 n en\gh room left on any ( ! #aab-;degree facets to m\nt a second l>ge mirror1 we sub/itut$ two small] mirrors & m\nt$ !m #abj degrees ap>t4 ,?is arrangem5t lets u "k f :i* mirror we see fla%es--! plane mirror gives "o fla% = ea* revolution ( ! satellite2 ! facet$ mirrors give two fla%es = ea* revolution ( ! satellite4 ,illu/ration3 ,sket*es ( ?ree reflect+ mirrors & _! locations on ! ,tel/> satellite4 ,! upp] plane mirror is set at #fh to ! sp9 axis2 ! l[] ones are facet$ to give reflect+ surfaces at #ie4 ,two ( ! satellite's six sol> aspect cells c be se5 )9 ! circul> cut-outs 9 ! mirrors4 ,h[ ,we ,record ,fla%es f ! ,mirrors ,n[ we _h f9ally f\nd a satisfactory way to reflect a tra9 ( t9y fla%es--mu* too fa9t to be se5 by ! nak$ eye--f ,tel/> z x pass$ across ! sky dur+ ! night4 ,b our ma9 aim 0 to record ! exact times :5 ^! fla% bur/s occurr$4 ,) ?is in=mation1 we c\ld1 us+ ! me?od we describ$ above1 tell v accurately bo? ! satellite's sp9 axis & its rate ( sp94 ,we d n h space to describe ! _m problems t _h to be solv$ 9 sett+ up ! equipm5t to record ! fla%es4 ,let u m]ely outl9e ! proc$ure t we f9ally devis$3 #a4 ,to pick up ! satellite's fla%es we use a #ab-;in*-ap]ture photoelectric telescope m\nt$ on a rad> trail] 7%[n 9 illu/ration bel[74 ,x is po9t$ by means ( pr$iction drive tapes produc$ by an electronic comput]2 ^! are bas$ on data f previ\s passes4 #b4 ,on cle>1 d>k nights :5 ! satellite is at relatively %ort range1 we c see x ) an auxili>y f9d] telescope1 & !n adju/ ! l>ge telescope precisely4 ,or1 if ! satellite's high-frequ5cy beacon has be5 turn$ on1 ! ,holmdel micr[ave ant5na c automatically po9t our l>ge telescope4 #c4 ,:5 fla%es ( light are pick$ up by ! telescope1 !y fall directly onto ! ca?ode ( a photomultipli] tube4 ,!y are !n filt]$ out f ! r&om light 9 ! night sky & amplifi$4 ,illu/ration3 ,twelve-in* telescope & electronics box m\nt$ on a rad> ant5na p$e/al at ,craw=d's ,hill4 ,?ree-in* sight+ telescope m\nt$ on top has s9ce be5 replac$ by six-in* telescope4 #d4 ,r ?an make a cont9u\s record+ ( ! output--"o night ?is w\ld h produc$ a record twelve miles long = u to pore ov]--we use an electronic trigg]4 ,?is is ! "t base ( an oscilloscope1 ^: sawtoo? output is set 9 op]ation only if a signal ( f\r volts or m is receiv$ 7photo bel[74 #e4 ,a p5 record] makes a cont9u\s l9e on a revolv+ drum1 ) a heat$ /ylus connect$ to a galvanomet] m>k+ a p]man5t record on heat-s5sitive pap]4 ,any signal output f ! oscilloscope is pick$ up by ! galvanomet] & causes ! p5 to make a sawtoo!d m>k2 :5 ! pap] is unroll$ f ! drum1 ^! m>ks are cle>ly visible z not*es 9 a s]ies ( o!rwise /raight l9es4 #f4 ,a syn*ron\s tim] m>ks ! *>t e t5 seconds1 & we are able to "t individual pulses ) a precision ( "o t5? ( a second4 ,because ! beg9n+ & end ( a tra9 ( pulses are n always di/9ct1 we c only det]m9e ! c5t] ( a bur/ ( fla%es--:i* we use z our mo/ important "t indication--to )9 two seconds4 ,h[ev]1 ?is is accurate en\gh1 = a *ange ( only "o degree 9 ! ori5tation ( ! satellite's sp9 axis w\ld *ange ! "t ( ! fla% bur/ c5t] by ab\t half a m9ute 7see bel[74 #g4 ,we use a second oscilloscope to *eck on :e!r ! signals we receive are g5u9e fla%es or j accid5tal /ray light4 ,?is oscilloscope has a long-p]si/5ce scre51 :i* we use z a tempor>y memory4 ,! pulses trac$ on its ca?ode ray tube are automatically photograph$ by a #ce-mm cam]a :ile !y p]si/ on ! scre54 ,we c !n exam9e ! photograph to see if ! pulses are g5u9e1 :i* we asc]ta9 f 7a7 _! %ape & size & 7b7 ! int]vals betwe5 successive pulses4 ,look+ at ! photographic record also confirms :e!r we are obs]v+ fla%es f ! #fh plane mirror or ! #ie facet$ mirrors4 ,we c calculate ! satellite's sp9 rate by measur+ ! int]vals betwe5 individual fla%es4 ,illu/ration3 ,g5]al view ( amplify+1 monitor+1 & record+ ge> t picks up gl9ts ( sunlight at ! ,craw=d's ,hill obs]vation /ation4 ,illu/ration3 ,enl>g$ portion ( a typical p5 record ( fla%es ( sunlight f ,tel/> mirrors1 %[+ a bur/ ( #ba gl9ts f ! #fh mirror record$ at #jc3dj3eh ,gre5wi* ,mean ,"t on ,augu/ #i1 #aifb4 ,syn*roniz+ vibration m>k sev5 l9es above ! record$ bur/ indicates ! "t #jb3ei3jj4 ,measur+ ! horizontal di/ance betwe5 consecutive sawtoo? m>ks tells u t ! sp9 rate is betwe5 #afc & #afd revolutions p] m9ute4 7,precise measurem5ts ( ! oscilloscope traces fix$ ! exact sp9 rate at ! "t ( ?is bur/ at #afc4fd revolutions p] m9ute47 ,results ,tel/> ,i 0 laun*$ on ,july #aj1 #aifb4 ,t ev5+1 beg9n+ on ! satellite's sev5? pass1 we 7 able to detect tra9s ( fla%es f ! mirrors4 ,we assum$ t1 s9ce ,tel/> _h be5 laun*$ almo/ exactly accord+ to plan1 its sp9 axis w\ld be p]p5dicul> to ! plane ( ! e>?'s orbit1 & we calculat$ :5 we %\ld see ! fla%es4 ,&1 ea* "t1 we actually saw !m )9 two m9utes ( ! times we _h pr$ict$--s we knew t ! sp9 axis 0 almo/ exactly :]e x %\ld be4 ,our measurem5ts h cont9u$ :5ev] ! wea!r & o!r conditions p]mitt$4 ,comb9+ read+s f ! bur/s ( fla%es & telemetry data f ! sol> aspect cells1 we h accurately plott$ ,tel/>'s sp9 axis2 x has cont9u$ to precess v mu* z we pr$ict$ x w\ld4 ,we h also se5 :at happ5s to ! sp9 axis :5 ! satellite's torque coil is turn$ on4 ,&1 by measur+ ! int]vals betwe5 fla%es1 we h made v precise measurem5ts ( ! sp9 rate1 :i* is gradually decreas+ mo/ly accord+ to s*$ule4 ,h[ev]1 ! plot is %[+ "s small unexpla9$ v>iations ( sp9 decay rate1 & a /udy ( !m w1 we hope1 ?r[ light on "s ( ! v>iations ( ! e>?'s magnetic field4 ,= future communications "w1 p>ticul>ly ) satellites at long] ranges1 x w\ld seem to be pref]able to use /iff]1 flatt] mirrors & to make !m f b]yllium r ?an alum9um alloy4 ,m accurate track+ means1 m obs]vatory sites1 & m p[]ful telescopes w also be ne$$4 ,b = ?is fir/ exp]im5tal use our little mirrors h work$ v well4 ,je(ry ,s4 ,c\rtney-,pratt 0 born 9 ,hob>t1 ,tasmania1 ,au/ralia1 & receiv$ a ,ba*elor ( ,eng9e]+ degree f ! ,univ]sity ( ,tasmania 9 #aidb & a ,ph4,d4 f ,cambridge ,univ]sity 9 #aidi4 ,he 0 also aw>d$ an ,sc4,d4 by ,cambridge 9 #aieh4 ,he jo9$ ,bell ,telephone ,laboratories 9 #aieh1 & has done rese>* 9 high-spe$ photography1 optics1 optical mas]s1 ! prop]ties ( mat]ials1 & ! physics ( ! contact ( solids4 ,,case ,,hi/ory ,,no4 #d ,h[ ,d ,we ,keep ,sol> ,cell ,p[] ,plants ,work+ 9 ,space8 ,k5ne? ,d4 ,smi? ,electronics ,eng9e]--,memb] ( ,/aff1 ,semiconductor ,device ,laboratory ,,! ,,problem ,be=e we le>n$ ab\t ! ,van ,all5 belts1 we expect$ t ! sol> cells us$ to p[] satellites w\ld la/ = _m ye>s 9 space4 ,we ?\ght !y w\ld be damag$ only by cosmic rays1 micrometeorites1 & occasional bur/s ( p>ticles f ! sun4 ,b :5 ! sol> plants ( "s ,am]ican satellites w5t out ( action aft] only a few weeks 9 orbit1 we realiz$ t 9 ! future sol> cell p[] units w\ld ne$ bett] protection f radiation damage4 ,we _h le>n$ t satellites--& p>ticul>ly m$ium altitude communications satellites--mu/ sp5d a lot ( "t 9 regions :]e !y w be /ruck by ?\s&s or ev5 millions ( high-spe$ radiation p>ticles ea* second4 ,?is fact =c$ u to *ange almo/ all our ?9k+ ab\t sol> p[] plants = satellites4 ,to make sure !y w\ld la/ = sev]al ye>s1 we _h to design new types ( sol> cells & devise new ways ( m\nt+ !m4 ,we also _h to revise our e/imates ( h[ mu* p[] we c\ld expect to get f our cells4 ,if a communications satellite is to g into regul> comm]cial s]vice1 x mu/ cont9ue work+ = sev]al ye>s 9 space4 ,! ,tel/> satellite1 h[ev]1 0 design$ z an exp]im5tal project1 & we decid$ t two ye>s w\ld be a reasonable lifetime to plan =4 ,:5 ,project ,tel/> began1 our problem 0 to develop sol> cells t w\ld op]ate 9 an environm5t subject to /rong radiation effects--& keep on op]at+ !re = two ye>s4 ,organiz+ ! ,"w ,our "w on ! sol> cells = ,tel/> ,i began 9 ,octob]1 #aifj4 ,) j a little m ?an a ye> to g be=e ! satellite _h to be ready1 !re 0 no "t to lose4 ,s we decid$ to break d[n ! ov]-all problem into ?ree p>ts3 --,f9d+ out h[ radiation w\ld affect v>i\s k9ds ( sol> cells2 --,mak+ exp]im5tal cells &1 :5 ! be/ _h be5 pick$1 det]m9+ ! be/ ways to make !m 9 ! l>ge quantities we w\ld ne$2 & --,develop+ ways to m\nt ! cells on ! ,tel/> satellite s t !y w\ld )/& ! /resses ( be+ laun*$1 ! effects ( radiation p>ticles1 & extreme *anges 9 temp]ature4 ,a diff]5t gr\p ( p began "w simultane\sly on ea* ( ^! ?ree p>ts ( ! problem1 ) ea* ( !m go+ ahead "u ! assumption t ! o!rs w\ld be successful4 ,ea* gr\p _h to f9d ! answ]s to _m v int]e/+ que/ions1 b s9ce our space is limit$ we c only discuss "s ( !m "h4 ,be=e do+ s1 h[ev]1 we mu/ say some?+ ab\t :at a sol> cell is & h[ x works4 ,te*nical ,backgr\nd on ,sol> ,cells ,!re are two ways ( mak+ a silicon sol> cell4 ,9 "o1 ! body ( ! cell is :at we call n-type silicon--t is1 pure silicon t has be5 dop$ ) a small numb] ( impurity atoms ( an elem5t su* z phosphorus or ars5ic 7f gr\p ,v ( ! p]iodic table74 ,?is k9d ( semiconductor#d conducts electricity by means ( a supply ( free-to-move electrons 7negative *>ges7 caus$ by ! pres5ce ( ^! impurity atoms4 ,to make a workable sol> cell f n-type silicon1 a ?9 surface lay] ( p-type silicon is =m$ by diffus+ atoms ( a mat]ial f gr\p ,,iii ( ! p]iodic table--usually boron--into ! silicon4 ,metallic contacts !n are made to ^! two regions4 ,?is k9d ( cell is kn[n z a p-on-n cell4 ,! second type ( sol> cell is j ! rev]se4 ,x beg9s ) a body ( p-type silicon 7) impurity atoms f a gr\p ,,iii elem5t7 & conducts electricity by means ( 8holes0--vacant sites :]e electrons might be b are n4 ,^! holes act z free-to-move positive *>ges4 ,we c make a sol> cell f ?is mat]ial by diffus+ a lay] ( n-type impurity1 su* z phosphorus1 into x4 ,we call ?is an n-on-p cell 7see ! figure bel[74 ,illu/ration3 ,con/ruction ( a silicon sol> cell ( ! n-on-p type 7?ickness ( n-lay] greatly exagg]at$74 titanium-silv] evaporat$ contact ) sold] dip f9i% antireflection coat+ contact gridd+ = l[] s]ies resi/ance #ae mil waf]1 p-type #j4d micron front lay]1 n-type ,! key to ! op]ation ( ei!r type ( sol> cell is ! junction betwe5 ! regions ( n-type & p-type mat]ial--:at we call ! p-n junction4 ,9 an actual n-on-p cell ?is junction is only ab\t tw5ty million?s ( an in* bel[ ! surface1 s9ce t is ! ?ickness ( ! n-lay]4 ,at ?is po9t1 :]e ! hole-ri* p-region meets ! electron-ri* n-region1 !re is a p]man5t1 built-9 electric field4 ,z %[n 9 ! figure bel[1 ! n-lay] has _m free electrons 7indicat$ by m9us signs7 & a few holes 7circl$ pluses71 :ile ! p-region has _m holes & a few electrons4 ,:5 ! cell is 9 equilibrium1 !rmal agitation causes "s holes to diffuse into ! p-region4 ,we call ^! /ray holes & electrons m9ority c>ri]s 7! circl$ pluses & m9uses 9 ! figure74 ,?us1 ! n-lay] has a slight positive *>ge & ! p-body has a slight negative *>ge2 ?is results 9 a diff]5ce 9 pot5tial across ! junction1 :i* 9 silicon am\nts to ab\t sev5-t5?s ( a volt4 ,illu/ration3 ,s*ematic diagram ( an n-on-p sol> cell4 ,9 ! n-lay]1 m9uses repres5t free electrons1 circl$ pluses are m9ority-c>ri] holes2 9 ! p-type body1 pluses repres5t holes1 circl$ m9uses are m9ority-c>ri] electrons4 ,sunlight is made up ( individual corpuscles ( en]gy call$ photons4 ,:5 ^! photons are absorb$ 9 or ne> a cell's p-n junction1 !y lib]ate bo? a free-to-move negative *>ge & a free-to-move positive *>ge--?is is call$ g5]at+ a hole-electron pair4 ,! electric field across ! p-n junction causes ! holes to fl[ to ! p-side & ! electrons to ! n-side ( ! b>ri]4 ,?is fl[ t5ds to make ! p-side positive & ! n-side negative1 s t1 :5 a load is connect$ betwe5 !m1 a useful ext]nal voltage 7am\nt+ to ab\t six-t5?s ( a volt7 is produc$1 & electric curr5t w fl[4 ,?us1 we h conv]t$ light en]gy into electrical en]gy4 ,only "p ( ! en]gy 9 light c be us$ to g5]ate an electrical output1 s9ce a good deal ( ! light /rik+ a cell is absorb$ z heat or is reflect$ f its surface4 ,! p]c5tage ( sol> en]gy t c be conv]t$ into usable electric p[] is call$ ! cell's conv]sion factor or effici5cy4 ,al?\gh ?is c !oretically be z high z #bb1 ! be/ cells we h made 9 ! laboratory h conv]sion factors ( only ab\t #ae1 & ! bett] comm]cial cells h effici5cies ( #ab or m4 ,al?\gh bo? p-on-n & n-on-p cells 7 made 9 e>ly laboratory /udies1 ! p-on-n cells gave a some:at high] output4 ,z a result1 all ! ,am]ican comm]cial sol> cells up to #aifj 7 ( ?is type1 & !y 7 us$ on all satellites be=e ,tel/> ,i4 7,russian satellites1 we believe1 h us$ n-on-p cells f ! beg9n+47 ,! ,u4,s4 ,army ,signal ,corps ,rese>* & ,developm5t ,laboratory1 h[ev]1 decid$ to make bo? p-on-n & n-on-p cells & comp>e _! p]=mance4 ,?is laboratory "w l$ to a surpris+ discov]y3 ,! n-on-p cells 7 sev]al times z resi/ant to en]getic p>ticle radiation z 7 comp>able p-on-n cells4 ,^! results 7 ann\nc$ 9 #aifj1 & confirm$ by our measurem5ts & ^? ( o!r laboratories4 ,! tim+ 0 v =tunate1 s9ce we _h j le>n$ ( ! greatly increas$ radiation haz>ds pres5t$ by ! ,van ,all5 belts4 ,f9d+ ,out ,ab\t ,radiation ,damage ,n[1 hav+ giv5 y a v brief acc\nt ( h[ a sol> cell works1 let u return to our ?ree-"p problem4 ,! fir/ objective 0 to /udy all ! aspects ( radiation damage4 ,to d ?is1 we _h to f9d out h[ mu* radiation ! ,tel/> satellite w\ld enc\nt]2 we ne$$ to e/imate ! conc5tration ( high-en]gy p>ticles--bo? electrons & protons--at v>i\s altitudes & locations4 ,sev]al gov]nm5t ag5cies are n[ c>ry+ on rese>* 9 ?is important area1 b at ! "t ( ! ,tel/> ,i laun* we did n "k exactly h[ mu* radiation ! satellite w\ld run into4 ,& ! high-altitude nucle> explosion ( ,july #i1 #aifb 7! day be=e ,tel/> ,i w5t into orbit7 may h increas$ ! quantity ( high-en]gy electrons inject$ into its pa?4 ,we also want$ to f9d out :e!r electrons & protons w\ld d ! same damage to sol> cells4 ,sev]al k9ds ( cells 7 expos$ at ,bell ,laboratories & at v>i\s univ]sity rese>* laboratories to a wide range ( radiation dosages4 ,! exp]im5ts %[$1 g5]ally1 t ! damage effects ( electrons & protons %\ld be ab\t ! same4 ,al?\gh protons are #ahdj times z massive z electrons1 !re are a great _m m electrons 9 ! ,van ,all5 belts1 s t an unprotect$ sol> cell w\ld be mu* m likely to be injur$ by electrons ?an by protons4 ,9 fact1 we f\nd t ! ,van ,all5 belt protons h s mu* en]gy t !y c g ?r\gh transp>5t %ield+ mat]ial z mu* z sev]al c5timet]s ?ick & /ill damage a sol> cell4 ,?us1 to scre5 our cells f protons we w\ld ne$ v ?ick transp>5t cov] plates1 & ?is add$ weight w\ld be intol]able4 ,s we decid$ to use no proton %ield+ at all4 ,) electrons1 ! situation is diff]5t2 !y are mu* light] & h mu* less en]gy4 ,also1 if _! en]gy is r$uc$ bel[ a c]ta9 level 7ab\t #ahj ?\s& electron volts7 electrons w n be able to knock silicon atoms out ( position1 & ?us _c h>m a sol> cell4 ,we exp]im5t$ ) a numb] ( diff]5t k9ds & ?icknesses ( cov] plates1 & f\nd t transp>5t mat]ial ) a mass ( #j4c gram p] squ>e c5timet] w\ld sl[ d[n electrons en\gh to make !m no problem4 ,ano!r radiation /udy help$ u take advantage ( ! fact t sol> cells respond diff]5tly to light ( diff]5t wave l5g?s4 ,if ! surface lay] ( a cell is extremely ?91 x w absorb blue1 gre51 & yell[ light well1 b may be mu* less s5sitive to ! deeply p5etrat+ r$ & infr>$ waves4 ,we exp]im5t$ ) n-on-p cells hav+ v %all[ p-n junctions1 expos+ !m to an extremely /rong radiation dosage4 ,! cells /ill respond$ v well to blue & gre5 light1 ev5 ?\gh mo/ ( _! response to infr>$ & r$ light 0 lo/4 ,^! f9d+s conv9c$ u t we %\ld "w to make our new cells z blue-gre5 s5sitive z possible1 s9ce !y 7 go+ to be expos$ to heavy radiation4 ,design+ & ,mak+ ! ,be/ ,sol> ,cells ,aft] x 0 discov]$ t ! n-on-p cell 0 m resi/ant to radiation1 we decid$ to make an all-out ef=t to develop an n-on-p cell t c\ld be manufactur$ 9 quantity = our new satellite4 ,s9ce we didn't "k :e!r we c\ld solve ?is problem 9 "t to meet ! ,tel/> ,i laun* date1 we 8h$g$0 by design+ ! new n-on-p cells to be ! same physical size 7"o by two c5timet]s7 z conv5tional p-on-n cells4 ,?us1 if ! n-on-p project hit a snag1 we probably c\ld use regul> p-on-n cells4 ,z y c imag9e1 mak+ a sol> cell to fit ! v high requirem5ts we _h set = ! ,tel/> satellite is n an easy job--& mak+ ^! cells by ! ?\s&s is ev5 m ( a task4 ,dur+ ,octob]1 ,novemb]1 & ,decemb] ( #aifj we c>ri$ on a cra% program 9 :i* we made hundr$s ( exp]im5tal cells 9 our laboratories1 us+ a v>iety ( mat]ials & _m diff]5t manufactur+ te*niques4 ,we p]fect$ a phosphorus diffusion process to develop ! v ?9 n-lay] 7ab\t "o =ty-?\s&? ( an in* ?ick7 t we ne$$ = our special blue-s5sitive n-on-p cells4 ,we also _h to devise an entirely new way to atta* ! metallic contacts to ! highly poli%$ surfaces ( our cells1 us+ a comb9ation ( titanium & silv]4 ,"s tricky manufactur+ problems also _h to be solv$ once ! ,we/]n ,electric ,company began to make ! l>ge quantity ( cells ne$$ = ! ,tel/> program4 ,= example1 dur+ ! diffusion ( ! n-lay] ( ! cell1 ! silicon slice is surr\nd$ by phosphorus p5toxide vapor1 :i* cov]s ! entire slice ) an 8n-sk940 ,?is sk9 mu/ be remov$ f ! bottom ( ! cell by et*+ or grit bla/+ be=e ! p-contact is appli$4 ,ano!r difficult problem occurr$ :5 we decid$ to give our cells an anti-reflection coat+4 ,because poli%$ silicon has a refractive index ne> #d & space has an index ( #a1 silicon w reflect ab\t #cd ( visible light f ! sun4 ,h[ev]1 if we apply an anti-reflection lay] onto ! silicon ?is p]c5tage ( reflection c be consid]ably decreas$4 ,we f\nd t ! be/ sub/ance = ?is purpose 0 a lay] ( silicon monoxide only ?ree-million?s ( an in* ?ick4 ,b x 0 only aft] q a bit ( tr\ble--& scrapp+ sev]al ?\s& cells--t we 7 able to get ?is coat+ to adh]e prop]ly 9 ! "r ?ickness4 ,m\nt+ ! ,cells on ! ,satellite ,! ?ird "p ( our problem _h to d ) f9d+ ! be/ ways to m\nt & protect ! cells on ! ,tel/> satellite itself4 ,s9ce a satellite's sol> p[] plant usually has sev]al ?\s& cells1 we f9d x be/ to m\nt ! cells 9 gr\ps1 or modules4 ,^! c be prete/$ z a unit aft] individual int]connections h be5 made4 ,= ,tel/> ,i1 we decid$ to m\nt ! #cfjj sol> cells 9 #ab-;cell modules l ^? %[n 9 ! figure bel[4 ,illu/ration3 ,! satellite uses #cjj modules ( twelve sol> cells1 9 gr\ps ( six or ?ree modules p] facet4 ,illu/ration3 ,l5g?wise diagram ( a sol> cell module1 %[+ h[ individual cells 7 fix$ 9 place4 ,ea* ( ! cells has a top contact along "o edge & a bottom contact all ov] its base1 s we 7 able to assemble ! #ab-;cell gr\ps l %+les1 ) ! bottom edge ( "o cell cov]+ ! top edge ( ! next1 leav+ only ! active area ( ea* cell expos$4 ,b ?is meant t ea* module w\ld be ov] f\r in*es long & only #ad ?\s&?s ( an in* ?ick--f> too weak to )/& /ress & vibration4 ,to support ! cells1 we decid$ to m\nt !m on a metalliz$ c]amic base4 ,b ?is pres5t$ a problem3 ,if ! cells 7 sold]$ directly to ! base1 ! diff]5t !rmal expansion rates ( ! silicon & ! c]amic w\ld cause ! /ructure to break dur+ ! cycles ( extreme *anges 9 temp]ature t ,tel/> w\ld pass ?r\gh4 ,we rem$i$ ?is by connect+ ea* cell to ! c]amic support by a ?9 ,u-%ap$ /rip ( silv] 7see above74 ,s9ce silv] has a mu* high] !rmal expansion coeffici5t ?an silicon1 we add$ t9y s&wi*es ( ,nilv> or ,inv> 7#cf nickel1 #fd iron7 :]e ! cells 7 atta*$4 ,) ?is m\nt+ me?od1 ! cell modules )/ood !rmal & me*anical %ocks mu* m sev]e ?an ^? !y w\ld und]go 9 actual use4 ,9 "o te/1 = in/ance1 an entire cell module ) its cov] plates 0 fir/ dipp$ 9 hot wat]1 !n plung$ into liquid nitrog5 at a temp]ature ( -#aie ,c5tigrade4 ,9 orbit1 ! temp]ature range = ! satellite 0 n expect$ to be m ?an f #hj to -#ajj;,c1 ) a rate ( *ange ( no m ?an ?ree degrees a m9ute4 ,f9ally1 we ne$$ to f9d ! "r k9d ( transp>5t protective cov] = ! ,tel/> sol> cells1 bo? to keep micrometeorites f damag+ ! s5sitive & v ?9 diffus$ lay] & to sl[ d[n ! incom+ electrons to nonde/ructive en]gy levels4 ,= micrometeorite protection1 only a ?9 lay] ( h>d transp>5t sub/ance 0 ne$$2 = electron protection1 ! cov] plates %\ld h a mass ( no less ?an #j4c gram p] squ>e c5timet] 7z we expla9$ above74 ,& !re 7 two o!r important consid]ations3 ,! mat]ial we us$ %\ld n be d>k5$ or discolor$ by prolong$ exposure to ultraviolet radiation1 & x %\ld h good !rmal conductance1 s t "s ( ! heat absorb$ by ! sol> cells c\ld be conduct$ out to ! cov] plates & re-radiat$4 ,all ^! requirem5ts l$ u to ! *oice ( cle>1 man-made sapphire4 ,al?\gh sapphire is m exp5sive & difficult to make ?an ! equival5t qu>tz or glass1 x only has to be #cj mils 7?ree hundr$s ( an in*7 ?ick4 ,twice ?is ?ickness w\ld be requir$ if qu>tz or glass 7 us$4 ,we h _h space to describe only a few ( ! ?+s involv$ 9 design+ a sol> cell p[] plant t w\ld "w unatt5d$ out 9 space4 ,we h n m5tion$ a good _m ( ! t\gh problems t _h to be work$ on4 ,b we are glad to report t we c\ld f9d answ]s to almo/ all our que/ions4 ,& ! mo/ significant answ] is %[n 9 ! figure bel[1 :]e y c see h[ ! ,tel/> ,i sol> p[] plant sl[ly dim9i%$ 9 p[] almo/ exactly z we pr$ict$ x w\ld4 ,illu/ration3 ,v gradual decay due to radiation effects ( ! ,tel/> ,i sol> cell plant 9 ! fir/ mon?s aft] ! satellite w5t into orbit2 x 0 extremely close to ! pr$ict$ rate 7solid l9e74 ,k5ne? ,d4 ,smi? 0 born 9 ,galesburg1 ,ill9ois1 & receiv$ a ,b4,a4 f ,pomona ,college 9 #aibh & an ,m4,a4 f ,d>tm\? ,college 9 #aicj4 ,he jo9$ ,bell ,telephone ,laboratories 9 #aicj1 & has work$ on ! developm5t ( proximity fuzes1 rad> bomb+ sy/ems1 broadb& micr[ave radio sy/ems1 & v>i\s semiconductor devices1 includ+ radiation-resi/ant sol> cells = ! ,tel/> satellite4 ,,case ,,hi/ory ,,no4 #e ,w\ld ,"t ,delay ,be a ,problem 9 ,us+ a ,syn*ron\s ,satellite8 ,pet] ,d4 ,brick] ,psy*ologi/--,memb] ( ,/aff1 ,behavioral ,rese>* ,laboratory ,,! ,,problem ,"o ( ! satellite communications sy/ems t has be5 propos$ w\ld make use ( /ation>y syn*ron\s satellites4 ,^! w\ld be precisely locat$ above ! e>?'s equator 9 orbits #bb1cjj miles high1 :]e !y w\ld circle ! e>? once e #bd h\rs1 & ?us appe> to rema9 /ation>y ov] a po9t on ! e>?4 ,!re are sev]al advantages to ?is type ( sy/em--! mo/ important be+ t we w\ld ne$ only ?ree satellites = communications betwe5 almo/ all ! inhabit$ regions ( ! e>?4 ,on ! o!r h&1 !re are sev]al problems 9 e/abli%+ a syn*ron\s sy/em4 ,j gett+ ! satellites into exactly ! "r places & keep+ !m 9 position is a =midable "o4 ,we also h some?+ ( a my/]y to cont5d )1 because ( ! trem5d\s di/ances t w\ld be involv$4 ,al?\gh we c communicate at spe$s close to t ( light--#ahf1jjj miles p] second--we _c g any fa/] ?an t4 ,y might ?9k t #ahf1jjj miles a second 0 fa/ en\gh = u1 & mo/ ( ! "t x is4 ,h[ev]1 if y s5d signals #bb1cjj miles up into ! sky1 transmit !m back to e>?1 p]haps s5d !m up aga9 to a second satellite1 & f9ally br+ !m #bb1cjj miles back d[n to e>?1 ev5 ! spe$ ( light may n be fa/ en\gh4 ,! delay w be only ab\t a second or s1 b x may--= "s k9ds ( communications--be long en\gh to cause tr\ble4 ,h[ mu* tr\ble1 we don't yet "k4 ,= "o-way signals su* z television1 a transmission delay ( ab\t "o second obvi\sly makes little or no diff]5ce4 ,b = two-way conv]sations on ! telephone1 :]e !re is rapid back-&-=? talk+1 ev5 ?is t9y am\nt ( "t delay may be a problem4 ,& !n aga91 x may n be4 ,!re h be5 a lot ( exp]im5ts to f9d out some?+ ab\t ?is delay problem1 & ^! h giv5 u a lot ( diff]5t answ]s4 ,"w is /ill go+ on1 & !re is /ill mu* to f9d out4 ,9 ?is *apt]1 we tell y ab\t "o small1 e>ly exp]im5t4 ,its results 7 n conclusive1 b !y %\ld give y "o example ( h[ to set up & c>ry out a typical exp]im5tal /udy on human behavior4 ,illu/ration3 ,typical circul> satellite orbit3 r is di/ance f c5t] ( e>? to satellite2 ,r is radius ( e>?4 ,h[ a ,syn*ron\s ,satellite ,w\ld ,"w ,= our purposes1 we w n be conc]n$ ) all ! problems ( laun*+ a syn*ron\s satellite into its prop] orbit4 ,b y may be curi\s :y we "k t ?is orbit mu/ be #bb1cjj miles high4 ,x c be calculat$ by us+ two basic =mulas f elem5t>y physics4 ,f ,newton's ,law ( ,gravitation we "k t ! velocity1 v1 ( a satellite mov+ 9 a circul> orbit#e w be v 77g,r7_/7r771 :]e ,r is ! radius ( ! e>?1 r is ! di/ance f ! c5t] ( ! e>? to ! satellite1 & g is ! accel]ation due to gravity 7see diagram above74 ,we also "k t ?is velocity mu/ be v 7#br7_/7,t71 s9ce ! di/ance ! satellite travels to complete an orbit is #br1 & ,t is ! "t ( "o complete revolution4 ,?us we h ! equality 77g,r7_/7r77 7#br7_/7,t71 &1 solv+ = r1 we get r 7g,r,t7_/7#d777 ,s9ce we are int]e/$ 9 a syn*ron\s satellite1 ,t 9 ?is case w be #bd h\rs4 ,we c n[ f9d r 7us+ g #cb feet p] second p] second & ,r #cifj miles71 & !n obta9 ! di/ance r - ,r1 :i* w be #bb1cjj miles4 ,by us+ our previ\s =mulas1 we also c f9d ! velocity ( a satellite mov+ 9 ?is orbit1 :i* w turn out to be v #fhgj miles p] h\r4 ,illu/ration3 ,"o possible me?od ( us+ syn*ron\s satellites4 ,signals f ,new ,york 7,n7 to ,p>is 7,p7 w\ld g via satellite ,s2 signals f ,new ,york to ,calcutta 7,c7 w\ld g via satellites ,s & ,s4 ,! illu/ration above gives a r\gh idea ( h[ a syn*ron\s satellite sy/em might be set up4 ,?ree communications satellites1 ,s1 ,s1 & ,s1 are above ! equator 9 fix$ positions equal di/ances ap>t & #bb1cjj miles up4 ,locat$ 9 ?is mann]1 !y w\ld cov] ! major "p ( ! e>?'s surface4 ,f a po9t directly b5ea? x1 ! di/ance w\ld be #bb1cjj miles to a satellite2 f o!r po9ts ! slant range w\ld be great]4 ,signals s5t f1 say1 ,new ,york 7po9t ,n7 to ,p>is 7po9t ,p7 w\ld be reflect$ via satellite ,s4 ,9 do+ ?is1 !y w\ld travel a total di/ance ( ab\t #df1jjj miles4 ,because we c't s5d signals any fa/] ?an ! spe$ ( light 7#ahf1jjj miles p] second71 x w\ld take at lea/ a qu>t] ( a second = a signal to g ?is f>4 ,= communicat+ a mu* great] di/ance1 say f ,new ,york to ,calcutta 7po9t ,c71 ! signal pa? w\ld use two satellites1 ,s & ,s4 ,9 ?is case1 ! total di/ance travel$ by a signal w\ld be m ?an #ij1jjj miles1 & ! "o-way "t delay w\ld be ab\t half a second4 ,! ,effects ( ,"t ,delay ,delays ( a qu>t]- or half-second h diff]5t effects on v>i\s k9ds ( communications4 ,h[ev]1 we are conc]n$ "h only ) :at !y might d to telephone conv]sations4 ,"t delay w affect conv]sations 9 two ways4 ,"o ( ^!--pure delay--dep5ds on ! nature ( spee* & ! way p use x to conv]se2 ! o!r--e*o--has to d ) ! nature ( ! _w's telephone sy/ems4 ,! fir/ effect c be illu/rat$ by an example4 ,suppose t ,george 9 ,p>is is talk+ to me 9 ,new ,york4 ,he says1 8,d y want to g80 & ,i answ] 8,yes0 imm$iately ^u he>+ ! ^w 8g40 ,b t ^w didn't arrive 9 ,new ,york until a qu>t] ( a second aft] ,george said x1 & my reply 0 delay$ ano!r qu>t]-second1 s ,george he>s my in/antane\s reply a half-second late4 ,"u "s circum/ances1 he might int]pret ?is delay to mean t ,i 0 less ?an en?usia/ic ab\t go+4 ,we don't "k exactly :at response times p expect 9 conv]sation1 or h[ mu* v>iation 9 su* int]vals !y c tol]ate4 ,b x has be5 assum$ t delays ( a half-second or m w\ld make a noticeable & p]haps di/urb+ diff]5ce4 ,a little lat] on1 ,i w describe an exp]im5t deal+ ) ?is fir/ effect4 ,b fir/ we mu/ briefly discuss ! second effect ( delay on telephone conv]sation1 to %[ :y we decid$ to try to isolate ! fir/ effect & /udy x sep>ately4 ,! ,e*o ,problem ,all ! _w's telephones are individually connect$ to ! re/ ( ! sy/em by :at we call two-wire local loops4 ,spee* travels 9 bo? directions on ! same wires ov] ^! local p>ts ( ! circuit4 ,9 o!r p>ts ( ! sy/em1 :]e spee* travels f>!r & mu/ be amplifi$1 x is c>ri$ ov] f\r-wire circuits4 ,^! consi/ ( two pairs ( wires1 "o = transmission 9 ea* direction4 ,at ! junctions :]e ! two-wire & f\r-wire p>ts ( ! telephone sy/em meet1 specially design$ trans=m]s1 call$ hybrid coils1 are us$4 ,x is impossible to h ^! junctions betwe5 two-wire & f\r-wire circuits always 9 p]fect balance1 s "p ( ! spee* t rea*es a local loop w be reflect$ back along ! pa? on :i* x arriv$4 ,unless a circuit has be5 specially treat$1 ?is reflect$ spee* w get all ! way back to :]e x />t$1 & ! talk] w he> an e*o ( 8 own voice4 ,:5 ! circuit is %ort en\gh1 ! e*o is he>d almo/ in/antane\sly1 & is n bo!rsome4 ,b :5 ! e*o is delay$ by a tw5tie? ( a second or m1 x c become extremely annoy+1 & ev5 tempor>ily de/roy "o's ability to speak coh]5tly4 ,telephone eng9e]s h long be5 aw>e t ?is e*o effect 0 pres5t on _! long-di/ance circuits1 & !y h n let x g un*eck$4 ,devices kn[n z e*o suppressors are in/all$ on circuits t h m ?an a critical am\nt ( delay4 ,!y are plac$ 9 a f\r-wire "p ( ! circuit1 :]e !re is "o-way transmission ov] ea* pair4 ,s9ce incom+ & outgo+ s\nds are us+ sep>ate pa?s1 an e*o suppressor c att5uate or %ut (f ! return pa? :5 spee* is com+ 9 on ! o!r pa?4 ,un=tunately1 e*o suppressors h effects ( _! own on transmission4 ,!y may1 = example1 cut (f "s spee* t %\ld be gett+ ?r\gh1 because !y c't di/+ui% x f e*o4 ,e*o suppressors c be made m sophi/icat$1 b :e!r !y c be made to op]ate m successfully ?an pres5t ones is n cle>4 ,& ! problem ( adapt+ !m to ! long delays ( syn*ron\s satellite circuits w require a great deal ( rese>* & developm5t ef=t4 ,exp]im5t+ ,) ,pure ,delay ,al?\gh we don't "k h[ good e*o suppressors c get1 we d "k t a long circuit ) ! be/ possible suppressors c\ld nev] be bett] ?an a circuit ( ! same l5g? t _h no e*os4 ,?is br+s u back to ! problem ( h[ s]i\s ! effect ( delay alone is on conv]sations4 ,if ! delay 9 a syn*ron\s satellite sy/em1 ev5 )\t any e*o1 made conv]sation all b impossible1 !re w\ld be little po9t 9 develop+ e*o suppressors = su* satellites4 ,?is "q look$ l "o t we c\ld answ]1 at lea/ 9 "p1 by exp]im5t+ ) special f\r-wire circuits t _h delay b no e*o4 ,! /rategy we adopt$1 !n1 0 to d "s exp]im5ts on pure delay :ile o!r p at ,bell ,telephone ,laboratories began to attack ! problem ( te/+ & improv+ e*o suppressors4 ,9 ! pages t foll[1 ,i w describe "o ( our exp]im5ts on ! pure delay problem4 ,m elaborate ones h be5 p]=m$ s9ce1 & !re w be m to come4 ,x %\ld n[ be cle> h[ ?is sort ( exp]im5t might be helpful to ! developm5t ( a syn*ron\s satellite communications sy/em4 ,if x %[$ pretty conv9c+ly t conv]sation 0 extremely difficult ) a pure e*o-free delay ( ab\t a second1 syn*ron\s satellites = two-way conv]sations w\ld be less practical4 ,on ! o!r h&1 if ! exp]im5t 7 to %[ t "s conv]sation1 at lea/1 c\ld be c>ri$ on )\t too mu* difficulty1 our results w\ld be less decisive4 ,we w\ld "k only t e*o-free delay$ circuits might sometimes be all "r4 ,b we w\ld n "k h[ bad !y 7 "u a v>iety ( conditions or h[ closely !y resembl$ a real circuit ) e*oes & e*o suppressors4 ,9 ei!r case1 ! exp]im5t w\ld h no be>+ on ! use ( syn*ron\s satellites = "o-way purposes1 su* z television4 ,design+ ! ,exp]im5t ,illu/ration3 ,record+ equipm5t us$ 9 ! exp]im5t4 delay 77_/7#cfj7 1 :]e is ! p]iod ( rotation 9 seconds 8,c p conv]se ov] an e*o-free1 f\r-wire circuit t has delay l t ( a syn*ron\s satellite80--t is "o way ( putt+ ! "q we isolat$ to /udy4 ,! next problem 0 to f9d a way ( sett+ up ?is "q 9 ! =m ( an exp]im5t ^: results might be int]pret$ z a mean+ful answ]4 ,! problem ( app>atus1 =tunately1 0 fairly simple4 ,two telephone sets 9 sep>ate rooms 7 connect$ by f\r wires1 ) "o pair go+ directly f ea* transmitt] to ! o!r receiv]1 s t no e*o w\ld g back ! way x came4 ,?is gave u ! 8e*o-free1 f\r-wire circuit0 we want$4 ,to simulate ! satellite1 ,i ins]t$ a magnetic delay device 7see sket*7 betwe5 "o ( ! transmitt]s & ! o!r receiv]4 ,?is _h a revolv+ drum on :i* spee* c\ld be record$ & !n play$ back a %ort int]val lat]4 ,by mov+ ! playback head1 ,i c\ld produce any am\nt ( delay up to two satellite b\nces' wor?4 ,at ?is po9t1 ! equipm5t 0 ready1 b !re 7 /ill two major problems3 7#a7 h[ to get p to conv]se ov] ! circuit 9 a natural way1 & 7#b7 :at to obs]ve & measure t w\ld give u an answ] to our "q4 ,:5 y ?9k ab\t ! fir/ problem1 y soon realize t x is h>d to say exactly :at a 8natural0 conv]sation is4 ,b ev5 if we c't describe x1 we c try to f9d examples ( x4 ,i exp]im5t$ ) sev]al ways ( mak+ p talk t c\ld be recogniz$ z unnatural3 ^w games1 li/-*eck+1 %ape description & recognition1 & a sy/em ( rew>ds = spurts ( talk4 ,none ( ^! s*emes seem$ to g5]ate ! real conv]sational int]play we want$4 ,f9ally1 ,i notic$ t my c[ork]s (t5 got involv$ 9 vigor\s conv]sations on political & social issues at ! lun* table4 ,s ,i circulat$ a que/ionnaire to help me pick pairs ( p :o might ent] into lively discussions on "o or m topics4 ,i arrang$ sev5 conv]sations ( ?is sort1 & !y became ! basic mat]ial ( my /udy4 ,only "o ( ^! lack$ suffici5t _s to yield good data1 & six out ( sev5 is a pretty good p]c5tage :5 y try to /udy human behavior 9 su* a free situation4 ,note t ! conv]s]s express$ ideas t came f )9 !m at ! "t--n f any ext]nal mat]ials--& t !y usually felt r /rongly ab\t :at !y 7 say+ to ! o!r fell[1 :o disagre$ & !re=e ne$$ "s conv9c+4 ,( c\rse1 ^! conv]sations d n repres5t ! :ole range ( possible conv]sations2 !y are only a small sample ( "o type4 ,?is doesn't limit ! tru? ( ! p>ticul> result we got1 b x does limit h[ f> we may g5]alize f ^! results4 ,:at ,%\ld ,we ,obs]ve8 ,y might ?9k we c\ld solve ?is problem simply by ask+ ! conv]s]s _! op9ions4 ,we f\nd out long ago1 h[ev]1 t ! op9ions y get are affect$ by a lot ( ?+s3 h[ y ask ! "q1 ! attitude ( ! respond5t1 & 8 unrelat$ exp]i5ces outside ! exp]im5t4 ,s we usually try a m subtle approa*4 ,9 ?is case1 my basic obs]vation 0 ( :at psy*ologi/s call escape behavior4 ,! conv]s]s 7 told t !y w\ld />t talk+ ov] a normal circuit1 & t delay w\ld be introduc$ at "s po9t4 7,! delay 0 ins]t$ 9 su* a way t an abrupt *ange c\ld n be notic$47 ,all ! conv]s]s _h pu%buttons = signal+ ! exp]im5t]4 ,if !y ?\ght !y notic$ a delay1 !y 7 told t x w\ld be remov$ if !y pu%$ ! button4 ,?us !y c\ld always escape f ?is possibly unpleasant condition4 ,my reason+ 0 ?is3 ,if ! conv]s]s f\nd x v difficult to talk ) delay 9 ! circuit1 !y w\ld surely pu% ! button soon aft] ! delay 0 introduc$4 ,on ! o!r h&1 any "t :5 !y cont9u$ to conv]se )\t pu%+ ! button--:ile delay 0 9 ! circuit--0 obvi\sly also a "t :5 ! delay did n make conv]sation impossible4 ,s we _h at lea/ "o measurable quantity--! "t tak5 to detect delay--:i* we c\ld int]pret z an answ] to our "q4 ,note t we c\ld tell if p pu%$ ! button 8j to be on ! safe side0 by see+ h[ (t5 !y did ?is :5 !re actually 0 no delay 9 ! circuit4 ,!re are j a few m necess>y details be=e we discuss ! results3 --,i record$ ! conv]sations = lat] analysis1 b ! conv]s]s knew t ! record+s w\ld be held 9 confid5ce4 --,! am\nt ( delay us$ 0 #a4b seconds1 :i* repres5ts ! total r\nd-trip delay = a circuit us+ two satellites1 includ+ ! delay 9 typical end connections on ! gr\nd4 ,we us$ ?is mu* delay because our prelim9>y te/s indicat$ t x w\ld be m likely to produce an effect ?an w\ld ! #j4f second delay 9 a "o-satellite l9k4 --,! entire #a4b seconds ( delay 0 put into "o ( ! l9es1 s9ce we _h discov]$ t1 :]e !re is no e*o1 conv]s]s _c tell ! diff]5ce betwe5 a delay ( #bt seconds 9 "o l9e & a delay ( t seconds 9 ea* ( two l9es4 ,i did ?is = ! sake ( conv5i5ce1 s t ,i c\ld introduce delay 9 ! quiet l9e :ile ! o!r "o 0 active4 --,aft] someone detect$ delay1 ,i remov$ x imm$iately & !n wait$ at lea/ a m9ute be=e putt+ x back 94 --,altoge!r1 ,i collect$ ab\t two h\rs ( conv]sation & introduc$ delay #bb times4 ,! ,results & ,:at ,!y ,mean ,n[ we c\ld answ] ! "q1 8,h[ long does x take p to detect #a4b seconds ( delay80 ,z y c see f ! table opposite1 ! times rang$ all ! way f #bj seconds to ov] #aj m9utes1 &1 9 two cases delay 0 n detect$ at all4 ,! results 9 ! table are also %[n 9 ! hi/ogram on ! next page1 :i* depicts h[ broadly ! detection times 7 di/ribut$4 ,to me1 "o ( ! mo/ int]e/+ ?+s is t ev5 p :o 7 able to detect delay quickly sometimes did n detect x = a c\ple ( m9utes4 ,= example1 ! pair ,k_/,g _h two times "u a m9ute1 "o ( #adc seconds1 & "o ( #dba seconds4 ,i int]pret _! two %ort times to mean t !y knew :at to look =1 s9ce !y made no incorrect responses :ile delay 0 n pres5t4 ,h[ev]1 _! long times seem to mean t !y sometimes didn't notice delay = q a :ile4 ,incid5tally1 only two responses 7 made dur+ ! total ( ab\t #dj m9utes :5 ,i did n introduce delay1 & ^! 8false al>ms0 7 by two ( ! fa/e/ pairs at true detection--,f_/,k & ,s_/,h4 ,l5g? ( ,"t ,be=e ,sev5 ,pairs ( ,talk]s ,c\ld ,detect #a4b ,seconds ( ,delay ,,pairs ,,( ,,talk]s ,,numb] ,,( ,,seconds ,,be=e ,,talk]s ,,detect$ ,,delay ,g_/,h #afa #bbd #ajg ,f_/,k #hg #fe #dc #bbj false al>m ,a_/,l #fah #ie #cfg ,f_/,t no detection aft] #ied seconds ,s_/,h #bbg false al>m #ij #ge #hc ,k_/,g #ch #dba #bj #adc ,s_/,w #beg #bbi no detection aft] #bfj seconds ,illu/ration3 ,data f table h be5 arrang$ 9 ?is hi/ogram to %[ wide range ( delay detection times t 7 record$ 9 ! exp]im5t4 ,ea* block repres5ts a s+le delay detection1 id5tifi$ by initials ( conv]s]s4 numb] ( cases #f ,s_/,h #e ,s_/,h #d ,s_/,h ,s_/,w #c ,k_/,g ,a_/,l ,s_/,h #b ,k_/,g ,f_/,k ,k_/,g ,f_/,k #a ,f_/,k ,f_/,k ,g_/,h ,g_/,h ,s_/,w ,a_/,l ,k_/,g ,a_/,l #j #j #ej #ajj #aej #bjj #bej #cjj #cej #djj #dej #ejj #eej #fjj #fej detection "t 7seconds7 ,n[1 to answ] our "q ab\t :e!r p c conv]se ov] our circuit1 we c say some?+ l ?is3 ,we h f\nd "s cases 7( a c]ta9 type ( conv]sation7 :]e p c use a circuit ) #a4b seconds ( e*o-free delay = ! am\nts ( "t li/$ 9 our table4 ,b !re are two important ?+s to rememb] ab\t our results3 --,! f9d+s are a non-negative answ] to ! orig9al "q1 8,c p conv]se ov] a f\r-wire1 e*o-free circuit t has delay l t ( a syn*ron\s satellite80 --,! exp]im5t applies only to f\r-wire1 e*o-free circuits1 & does n help ) ! problem ( improv+ e*o suppressors or ) t ( f9d+ out h[ good syn*ron\s satellite circuits ) ! be/ possible e*o suppressors w\ld be if !y 7 us$ to int]connect ! _w's telephones4 ,s9ce we didn't get a 8no0 answ] to our "q1 we h be5 enc\rag$ to d m exp]im5ts ) o!r subjects & o!r types ( conv]sations4 ,we also h begun to look = m ?an a yes-or-no answ]2 we n[ want to f9d out h[ s]i\s v>i\s am\nts ( pure delay w\ld be4 ,"s ( my colleagues h be5 work+ on ?is problem by furni%+ special f\r-wire telephones to a gr\p ( p1 s t e*o-free delay c be ins]t$ 9 ! l9e :5 "o memb] ( ?is te/ gr\p calls ano!r memb]4 ,_! exp]im5t has confirm$ our f9d+ t conv]sation ) a r\nd-trip pure delay ( #a4b seconds is n impossible1 b x has also %[n t ! degradation ( conv]sation t results is n trivial4 ,rec5tly an int]national committee on comm]cial telephone /&>ds set ! maximum p]missible e*o-free delay 7r\nd-trip7 at #j4g seconds4 ,h[ev]1 ! se>* = a m precise evaluation is /ill go+ on4 ,pet] ,d4 ,brick] 0 born 9 ,scranton1 ,p5nsylvania1 & receiv$ an ,a4,b4 f ,bucknell ,univ]sity 9 #aiej & an ,m4,a4 9 #aieb & a ,ph4,d4 9 #aied f ! ,johns ,hopk9s ,univ]sity4 ,he jo9$ ,bell ,telephone ,laboratories 9 #aied1 & has be5 engag$ 9 psy*ological /udies ( telephone color pref]5ces1 pu%button set designs1 voice id5tification1 & transmission quality evaluation4 ,,case ,,hi/ory ,,no4 #f ,h[ ,c ,we ,repair an ,orbit+ ,satellite8 ,e4 ,j>$ ,reid ,electrical ,eng9e]--,memb] ( ,/aff1 ,satellite ,design ,dep>tm5t ,,! ,,problem ,x is h>d en\gh to fix a new piece ( sci5tific equipm5t :5 x goes out ( ord] 9 ! laboratory4 ,& :5 ! equipm5t is sail+ ar\nd ! e>? a c\ple ( ?\s& miles up 9 ! sky a repair job ought to be impossible4 ,b dur+ ! la/ two mon?s ( #aifb we f\nd ?is n to be true at all4 ,t 0 :5 ! ,tel/> ,i satellite began to misbehave & ev5tually w\ld n obey ! comm&s we s5t x f ! gr\nd4 ,?is pres5t$ u ) a nice little problem3 ,we _h to f9d out exactly :at 0 wrong ) ! satellite & !n--! really t\gh job--devise a way to cure ! tr\ble4 ,we 7 able1 f9ally1 to d bo? ^! ?+s1 aft] a comb9ation ( logical d$uction1 trial-&-error exp]im5tation1 & laboratory te/+--plus a c]ta9 am\nt ( pla9 good luck4 ,our 8cure10 un=tunately1 turn$ out to be only a tempor>y "o1 = our pati5t _h a relapse "s weeks lat]4 ,h[ev]1 ! /ory ( h[ we w5t ab\t do+ our nev]-be=e-attempt$ task %\ld give y an idea ( ! ?+s y h to improvise 9 ! laboratory :5 an exp]im5t doesn't "w out exactly z y _h plann$4 ,! ,tel/> ,comm& ,circuit ,z %[n on pages #cb & #cc1 ! op]ation ( ! ,tel/> ,i satellite 0 controll$ by ord]s s5t f ! gr\nd on a frequ5cy ( #abc megacycles4 ,fifte5 diff]5t comm&s c\ld be giv5 to ! satellite1 ea* a cod$ signal made up ( a s]ies ( ones & z]os4 ,! signals1 z y c see 9 ! table bel[1 turn on or (f ! radiation exp]im5ts1 ! telemetry1 ! communications equipm5t1 & ! ori5tation coil4 ,^! are important functions1 & we want$ !m to be go+ on :5 !y 7 ne$$4 ,b we did n want !m to be op]at+ cont9u\sly4 ,comm& 0 ! only ,tel/> ,i function t we felt _h to be 8r$undant10 s two duplicate *a9s ( compon5ts 7 provid$4 ,z y c see 9 ! block diagram on ! next page1 ! satellite has two radio receiv]s 9 p>allel1 s t "o c op]ate if ! o!r fails4 ,!re are also two comm& decod]s1 :i* take ! pulse-cod$ signals f ! receiv]s & translate _! z]os & ones into usable in/ructions4 ,9 ! comm& swit*+ control1 ^! in/ructions op]ate n9e relays t turn on or (f ! p[] to all ! electronic circuits except ! comm& receiv+ *a91 :i* op]ates cont9u\sly4 ,tel/> ,i's telemetry unit report$ back #aab measurem5ts e m9ute ov] ! #acf-megacycle frequ5cy4 ,^! told bo? :at ! satellite enc\nt]$ 9 space & ! condition ( ! satellite's own compon5ts--z indicat$ by a v>iety ( diff]5t s5sors4 ,! telemetry also gave a *eck on :e!r ! comm&s s5t to ! satellite 7 actually obey$4 ,! ,fifte5 ,tel/> ,comm&s ,,comm& ,,function ,a ,turns on travel+-wave tube filam5t voltage ,b ,turns on travel+-wave tube helix & collector voltages2 en]gizes all transi/or circuits associat$ ) communications exp]im5ts ,,aa ,turns (f travel+-wave tube helix1 collector1 & filam5t voltages2 de-en]gizes transi/or circuits ,c ,turns on travel+-wave tube by apply+ anode voltage ,,cc ,turns (f travel+-wave tube anode voltage ,d ,turns on telemetry & en]gizes radiation exp]im5t circuits ,,dd ,turns (f telemetry & de-en]gizes radiation exp]im5t circuits ,e ,turns on curr5t 9 ori5tation torque coil ,,ee ,turns (f curr5t 9 ori5tation torque coil ,f ,connects telemetry encod] ,no4 #a to circuit ,,ff ,connects telemetry encod] ,no4 #b to circuit ,,ss ,p]=ms duties ( ,,aa1 ,,cc1 ,,dd1 ,,ee1 & ,,ff2 de-en]gizes #acf-mc beacon transmitt] & removes all load f /orage batt]y ,s ,connects /orage batt]y back into ! circuit & en]gizes ! #acf-mc beacon transmitt] ,t#a ,turns (f comm& receiv] & decod] ,no4 #b = #ae seconds1 s t comm& receiv] & decod] ,no4 #a c be te/$ ,t#b ,turns (f comm& receiv] & decod] ,no4 #a s t ,no4 #b c be te/$ ,illu/ration3 ,?is block diagram ( ,tel/> ,i's comm& circuit %[s ! r$undant receiv] & decod] *a9s1 ,no4 #a & ,no4 #b1 :i* are f$ ! comm& signals f ! gr\nd t are pick$ up by ! ,,vhf ant5na4 ,decod$ in/ructions g to ! comm& swit*+ control1 :i* op]ates relays to turn equipm5t on or (f4 ,reports on ! op]ation ( ?is control are s5t back by telemetry to ! gr\nd /ation along ) in=mation f ! satellite's s5sors4 ,,vhf ant5na diplex] comm& receiv] ,no4 #a comm& decod] ,no4 #a ,t#a comm& comm& receiv] ,no4 #b comm& decod] ,no4 #b ,t#b comm& comm& swit*+ control 7op]ates relays7 ,s-,,ss relay ,d-,,dd relay o!r relays #acf-mc beacon transmitt] ,,ss op5 ,s close telemetry ,,dd op5 ,,ss op5 ,d close s5sors 7radiation detectors1 p>ticle c\nt]s1 sol> aspect cells1 !rmi/ors1 etc47 p[] supply sol> cell p[] plant /orage batt]y p[] plant ,,ss op5 ,s close ?r\gh o!r relays to communications circuits & ori5tation torque coil ,:at ,w5t ,wrong ,) ,tel/> ,i ,dur+ ,tel/> ,i's fir/ two mon?s 9 orbit1 ! only indication ( tr\ble cropp$ up 9 "o ( ! comm& op]ations4 ,telemetry told u t ! satellite 0 no long] execut+ ! ,t#b comm&4 ,?is meant t we c\ld n tempor>ily disconnect comm& *a9 ,no4 #a to *eck ! p]=mance ( *a9 ,no4 #b4 ,!n1 a %ort :ile lat]1 ,no4 #b began to give int]mitt5t op]ation4 ,f9ally x fail$ completely4 ,at ! "t1 we didn't "k :y ?is _h happ5$1 b1 s9ce ! satellite's o!r comm& *a9 /ill seem$ to be op]at+ normally1 we 7 n v worri$4 ,h[ev]1 9 ! middle ( ,novemb] #aifb comm& *a9 ,no4 #a also began to be int]mitt5t4 ,we w\ld s5d a comm& b get no response f ! satellite2 only aft] we repeat$ x a few times w\ld ! satellite f9ally d :at x _h be5 told to d4 ,n[ !re 0 some?+ to be conc]n$ ab\t4 ,&1 if *a9 ,no4 #a %\ld fail1 we _h to make sure t ,tel/> w\ld be left 9 a favorable op]at+ condition4 ,we didn't want ! satellite's communications equipm5t to be left on )\t our be+ able to turn x (f--?is w\ld keep a cont9u\s dra9 on ! p[] supply4 ,z we fe>$ x w\ld1 ! o!r comm& circuit w5t out ( commission on ,novemb] #bcrd4 ,h[ev]1 :5 ?is happ5$1 ! communications circuits _h be5 turn$ (f1 al?\gh ! comm& *a9s !mselves & ! telemetry rema9$ on4 ,?is meant t we c\ld /ill try to s5d comm&s1 ! condition ( ! satellite c\ld /ill be monitor$ by telemetry1 & ! sol> cells c\ld /ill supply useful p[]4 ,b1 s9ce we c\ld n turn ! communications equipm5t on1 ,tel/> ,i c\ld no long] be us$ = transatlantic television or any ( ! exp]im5ts we _h be5 c>ry+ on successfully s9ce ,july4 ,look+ = ! ,tr\ble ,spot ,at ?is po9t a numb] ( ,bell ,telephone ,laboratories eng9e]s began to analyze ,tel/>'s tr\bles4 ,z y c imag9e1 we _h a r difficult problem4 ,we obvi\sly c\ld nei!r g up & look at ,tel/> nor br+ x d[n = an ov]haul on ! gr\nd4 ,we c\ld only s5d diff]5t comm&s to ! satellite & wat* ! telemetry data to see :at1 if any?+1 happ5$4 ,aft] *eck+ ! satellite's o!r equipm5t1 we 7 happy to f9d t ev]y?+ except ! comm& *a9s 0 9 good condition4 ,s we decid$ ! tr\ble _h to be "o ( five possibilities3 --excessive electronic 8noise0 9 ! satellite1 :i* _h block$ ! comm& receiv]s2 --extreme temp]ature v>iations1 :i* _h caus$ a jo9t to exp&1 contract1 & f9ally break2 --a loose connection2 --sl[ ag+ ( an electronic compon5t2 --det]ioration ( a compon5t f excessive radiation bomb>dm5t4 ,we c\ld quickly n>r[ ?is li/ d[n4 ,telemetry indicat$ t ! receiv] 0 n be+ block$ by noise4 ,reports f ! temp]ature-measur+ !rmi/ors told u t inside ! satellite ! temp]ature 0 #ge degrees ,fahr5heit1 j z x %\ld be4 ,a loose connection 0 v unlikely1 because e "o _h be5 made by exp]t wirem51 exam9$ by tra9$ inspectors1 & !n completely encapsulat$ 9 polyure?ane foam4 ,ag+ also seem$ v improbable1 s9ce all ! compon5ts _h be5 individually te/$ & select$ = ! highe/ reliability & longe/ life4 ,! ,villa93 ,radiation ,?is left only radiation damage4 ,we _h o!r good reasons to suspect ?is1 too4 ,z f> back z ,octob] #aifa1 sci5ti/s at ,bell ,labs & ,brookhav5 ,national ,laboratories _h made an important discov]y ab\t ! effect ( radiation on a transi/or4 ,!y f\nd t1 :5 radiation p5etrates ! out] %ell ( a transi/or & ionizes ! gases inside1 electrically *>g$ p>ticles 7ions7 t5d to collect on ! surface & *ange ! transi/or's electric prop]ties4 ,?is effect is p>ticul>ly noticeable :5 a transi/or is op]at+ "u rev]se bias voltage4 ,we knew t "s ( ! #cg transi/ors us$ 9 ea* ,tel/> ,i decod] circuit 7 op]at+ "u cont9u\s rev]se bias & t !y also _h less metal %ield+ ?an did ^? semiconductors 9 ! telemetry & receiv] circuits4 ,tel/>'s radiation detectors _h be5 tell+ u t ! conc5tration ( high-en]gy electrons ne> ! inn] edge ( ! ,van ,all5 belt 0 great] ?an we _h expect$4 ,we n[ "k ?is may h come z a result ( man-made high-altitude nucle> explosions1 "o ( :i* took place ! day be=e ,tel/> ,i 0 laun*$4 ,b we _h _h no reason to anticipate ?is extra radiation--x 0 m ?an "o hundr$ times ! pr$ict$ level--:5 we te/$ ! transi/ors to be us$ 9 ,tel/> ,i4 ,s we 7 n too surpris$ t !y 7 m susceptible to radiation damage ?an we _h ?\ght !y w\ld be4 ,all ?is seem$ to give u a !oretical explanation = ! tr\ble4 ,s1 aft] ,novemb] #bcrd1 we began look+ = laboratory evid5ce to confirm our radiation !ory4 ,fir/1 two eng9e]s travel$ d[n to ,johannesburg1 ,s\? ,africa4 ,at ?is "t ! highe/ po9t ( ,tel/>'s orbit--:5 x passes ?r\gh ! lea/ ,van ,all5 belt radiation--0 ov] ! s\!rn hemisph]e1 & x seem$ a good idea to comm& ! satellite :5 x 0 "u ! condition ( l[e/ radiation & see if any?+ w\ld happ54 ,h[ev]1 ev]y?+ ! eng9e]s tri$ prov$ fruitless4 ,illu/ration3 ,a duplicate ( "o ( ,tel/> ,i's comm& decod]s1 conta9+ #cg transi/ors & #aia diodes1 be+ plac$ 9 a small elevator t w l[] x into a gamma radiation *amb]4 ,at our ,murray ,hill1 ,new ,j]sey1 laboratories we work$ on a diff]5t approa*4 ,we expos$ transi/ors l ^? us$ 9 ! decod]s to l>ge doses ( radiation4 ,we also expos$ entire sp>e decod] units to accel]at$ radiation to f9d out :]e _! weake/ po9ts 7 7see illu/ration74 ,& !n we built & te/$ decod]s us+ radiation-resi/ant transi/ors to see if !y work$ bett]4 ,aft] a week ( int5sive laboratory "w1 we _h "s pretty good evid5ce4 ,! te/s ( individual transi/ors def9itely %[$ t heavy radiation w\ld cause !m to det]iorate4 ,te/+ ( ! complete decod]s also l$ to "s failures1 &1 :5 we analyz$ !m1 !y turn$ out to be ! k9d t w\ld be caus$ by faulty transi/ors4 ,we also discov]$ t ! mo/ s5sitive "p ( a decod] circuit 0 ! z]o gate1 :i* recognizes ! z]os 9 ! "o-&-z]o code t comm&s ! satellite4 ,illu/ration3 ,a typical comm& signal s5t to ,tel/> ,i4 ,x consi/s ( sev5 pulses3 a ?ree-unit 8/>t0 pulse & a b9>y code made up ( ?ree two-unit 8"o0 pulses & ?ree "o-unit 8z]o0 pulses4 ,fool+ ! ,decod] ,n[ we ?\ght we knew ! guilty compon5t1 b ! h>de/ job /ill lay ahead ( u4 ,we _h to d some?+ to ! comm&s s t !y w\ld bypass ?is tr\blesome z]o gate4 ,ea* ( ! fifte5 satellite comm&s is a b9>y code ( sev5 pulses1 z illu/rat$ 9 ! diagram above4 ,! fir/--! />t pulse--is ?ree units wide4 ,!n foll[ six m pulses ( :i* ?ree are two units wide 7"o pulses7 & ?ree are "o unit wide 7z]o pulses74 ,! arrangem5t ( ?is gr\p ( six ones & z]os det]m9es ! p>ticul> comm&4 ,ea* "t a "o pulse arrives at ! decod]1 a "o gate c\nts ! pulse & /ores a "o 9 its memory4 ,a z]o gate c\nts ! z]o pulses1 b does n /ore any?+4 ,s1 if ! z]o gate is block$1 ! decod] w n c\nt ! z]os 9 any ( ! cod$ comm&s & ?us _c decode !m prop]ly4 ,illu/ration3 ,! special 8not*$ "o0 pulse t 0 inv5t$ to fool ,tel/> ,i comm& decod]4 ,:at c\ld be done ab\t ?is8 ,! answ] seem$ to be to devise a new type ( pulse--a pulse t w\ld be en\gh l a "o s t x w\ld pass ?r\gh ! "o gate & advance ! c\nt]1 b1 at ! same "t1 be en\gh unlike a "o s t ! "o gate w\ld n /ore x 9 its memory4 ,?is l$ to ! inv5tion ( ! special long pulse ) a dip or not* 9 x t is %[n 9 ! diagram above4 ,:5 we te/$ x 9 ! laboratory on "o ( ! duplicate decod]s we _h expos$ to radiation1 ?is new not*$ pulse work$ z we hop$ x w\ld4 ,x pass$ ?r\gh ! "o gate & advanc$ ! c\nt]1 b 0 n /or$ z a "o 9 ! "o gate's memory4 ,?us x fool$ ! decod] by do+ j :at a z]o is suppos$ to d1 ev5 ?\gh x _h gone ?r\gh ! "o gate r ?an ! z]o gate4 ,illu/ration3 ,magnetic tapes ( special codes us+ not*$ ones 9 place ( z]os be+ prep>$ = use4 ,b ! real te/ 0 yet to come4 ,special modifi$ signals = two ( ! fifte5 ,tel/> comm&s1 us+ our new not*$ ones 9 place ( ! usual z]os1 7 put on magnetic tape 7see photograph74 ,!n1 on ,decemb] #bj?1 :5 ,tel/> made its #adibnd pass ov] ,&ov]1 ,ma9e1 a gr\p ( tir$ eng9e]s huddl$ ab\t ! mass ( equipm5t !y _h assembl$4 ,f9ally1 on ! ?ird try1 ! not*$ pulses 7 successful2 ,tel/>'s telemetry fla%$ back ! ^w t ! prop] relay _h op]at$ ^u comm&4 ,remov+ ! ,ionization ,we n[ want$ to get ,tel/> to d some?+ t _h seem$ to "w 9 ! laboratory4 ,! transi/ors mo/ affect$ by radiation 7 ^? op]at+ "u cont9u\s rev]se bias1 to ^: surfaces unwant$ ions 7 attract$4 ,if we remov$ ! voltage f ^! transi/ors1 we felt t ! ionization lay] w\ld be dissipat$1 & !y w\ld act normally aga94 ,our plan 0 to prep>e a complete tap$ program ( all fifte5 comm&s1 & c>efully disconnect ,tel/>'s /orage batt]y 7us+ comm& ,,ss74 ,!n1 :5 ! satellite w5t into eclipse1 !re w\ld be no p[] available f ! sol> cells ei!r1 &--if our calculation 0 "r--! complete lack ( voltage ought to re/ore ! transi/ors to work+ ord]4 ,?is 0 a haz>d\s proc$ure1 = if some?+ w5t wrong we might h a completely sil5t satellite on our h&s4 ,z x turn$ out1 an accid5t did happ5--b "o ( a diff]5t & mu* m =tunate k9d4 ,on ,decemb] #bg? ,tel/> mis9t]pret$ our 8trick0 comm&s & disconnect$ its own batt]y be=e we ask$ x to4 ,!n1 z ! satellite w5t into ! e>?'s %ad[1 we held our brea? :ile all its p[] /opp$ & ! telemetry w5t sil5t4 ,b1 z we _h hop$1 a re/ p]iod ) all p[] remov$ f ! det]iorat$ transi/ors app>5tly made !m "w almo/ normally once aga94 ,on ,janu>y #a1 #aifc1 we 7 able to disconnect ! batt]y 9 regul> fa%ion--t is1 us+ ! "o-&-z]o code4 ,aft] ?is 0 done1 & all p[] _h be5 remov$1 bo? decod]s aga9 w\ld op]ate :5 giv5 normal comm&s 7actually1 ! fir/ "o re/or$ to duty 0 decod] ,no4 #b1 :i* _h gone out ( ord] fir/1 back 9 ,augu/74 ,back to ,normal--,= a ,"t ,= m ?an a mon? ,tel/> ,i behav$ z x %\ld1 & our communications exp]im5ts1 includ+ television broadca/s1 7 resum$ on ,janu>y #crd4 ,dur+ ?is "t we us$ bo? normal comm&s & our special not*$-pulse modifi$ comm&s4 ,:5ev] normal comm&s became int]mitt5t we us$ ! modifi$ comm&s to disconnect ! batt]y = sev]al eclipses4 ,our good =tune1 h[ev]1 did n la/4 ,cont9u$ exposure to radiation app>5tly l$ to fur!r damage to ,tel/> ,i's transi/ors4 ,by ,febru>y #ad?1 disconnect+ ! /orage batt]y no long] return$ ! decod] to normal1 & we c\ld op]ate only ) our modifi$ comm&s4 ,&1 on ! #ba/1 ! satellite app>5tly mis9t]pret$ a comm&1 disconnect$ its /orage batt]y1 & w5t sil5t4 ,s9ce !n1 none ( our modifi$ comm&s has be5 able to br+ back its voice4 ,!re is /ill a possibility t ,tel/> ,i may recov] if x rema9s out ( ! high-radiation "p ( space = a long en\gh p]iod--b z "t goes by ?is appe>s less likely4 ,h[ev]1 our "w 0 n 9 va94 ,because we p9po9t$ ! effects ( radiation on ! transi/ors 9 ,tel/> ,i1 ?is problem 0 c\nt]act$ on ! ,tel/> ,,ii satellite laun*$ on ,may #g1 #aifc 7see page #ca74 ,to avoid ! wor/ ( ! radiation effects1 ! second ,tel/> is 9 a consid]ably l>g] orbit1 :i* causes x to sp5d less "t 9 ! heavie/ high-en]gy ,van ,all5 belt regions4 ,x c>ries new radiation detectors ) mu* great] measur+ capacity4 ,& 9 "o ( ,tel/> ,,ii's comm& decod]s we are us+ a new type ( transi/or1 :i* we hope w n be affect$ ne>ly z mu* by radiation z 7 ! ones 9 ,tel/> ,i's ill-fat$ decod]s4 ,e4 ,j>$ ,reid 0 born 9 ,h>t=d1 ,connecticut1 & receiv$ a ,b4,s4 f ,tr9ity ,college 9 #aief1 a ,b4,e4,e4 f ,r5ssela] ,polyte*nic ,in/itute 9 #aieg1 & an ,m4,e4,e4 f ,new ,york ,univ]sity 9 #aiei4 ,he jo9$ ,bell ,telephone ,laboratories 9 #aieg1 & has work$ on ! design & te/+ ( ! ,"t ,assignm5t ,spee* ,int]polation 7,,tasi7 sy/em = ! transatlantic cable1 z well z on transi/or circuits = ! ,tel/> satellite4 ,a ,f9al ,note to ! ,read] ,n[1 hav+ read ,"p ,,ii ( ,satellite ,communications ,physics1 y %\ld h an idea h[ we pr$ict ! orbit ( an artificial satellite & h[ we f9d out :]e x po9ts :ile pass+ a ?\s& miles above our heads4 ,y c see h[ we pick ! be/ mat]ial to cov] its surface ) & h[ we protect its sol> cells f ! haz>ds ( space4 ,& y h wat*$ ! /eps we w\ld take :5 our satellite /ops work+ prop]ly4 ,x w\ld1 we admit1 take a little m exp]i5ce to solve problems l ^! on y\r own--& to deal ) all ! o!r complications ( satellite communications4 ,b we hope our brief glimpses into ! laboratory h %[n :at ?is exp]i5ce might be l4 ,our six case hi/ories h only scrat*$ ! surface1 b !y %\ld give y a good idea ( ! fasc9at+ "w t goes into practical sci5ce & eng9e]+4 ,!y %\ld %[ t some?+ l ,project ,tel/> doesn't succe$ only because ( f>-sight$1 imag9ative ?9k+--nor only because ( +5i\s eng9e]+4 ,x draws ^u ! be/ ( bo? ( ^!4 ,along ! way1 we hope y h notic$ "s important guidepo/s--?+s l ,newton's law ( gravitation1 ! law ( reflection ( light1 ! ,/efan-,boltzmann law4 ,!y typify ! basic pr9ciples ( physics t eng9e]s & sci5ti/s1 :atev] !y d1 mu/ always keep 9 m9d4 ,no matt] h[ exotic or up-to-!-m9ute ! application1 ! gr\nd rules ( physics mu/ be foll[$4 ,if we h conv9c$ y ( ?is1 we h done :at we set out to d6 ,sugge/$ ,read+ ,if y w\ld l to read fur!r ab\t satellite communications 9 g5]al or get "s in=mation ab\t ! case hi/ories 9 ,"p ,,ii1 y may be int]e/$ 9 us+ ! foll[+ read+ li/4 ,! ref]5ces "u ea* ( ! subhead+s are li/$ *ronologically2 !y include books1 reports1 te*nical pap]s1 & magaz9e articles4 ,z y c see1 "s ( ^! ought to be und]/&able by almo/ anyone1 b o!rs are q te*nical 9 nature4 ,= fur!r backgr\nd 9 ! basic physical pr9ciples t are discuss$ 9 ,"p ,,ii1 y may ref] to _m good high s*ool & college physics texts4 ,an increas+ numb] ( useful physics books--bo? orig9als & repr9ts--are n[ be+ publi%$ 9 pap]back =m4 ,satellite ,communications ,ar?ur ,c4 ,cl>ke1 8,extra-,t]re/rial ,relays--,c ,rocket ,/ations ,give ,_w-,wide ,radio ,cov]age810 ,wireless ,_w1 ,octob] #aide1 page #cje4 ,john ,r4 ,pi]ce1 8,orbital ,radio ,relays10 ,jet ,propulsion1 ,april #aiee1 page #aec4 ,john ,r4 ,pi]ce & ,rudolf ,kompfn]1 8,transoceanic ,communication by ,means ( ,satellites10 ,proce$+s ( ! ,i4,r4,e41 ,m>* #aiei1 page #cgb4 ,john ,r4 ,pi]ce1 8,exotic ,radio ,communications10 ,bell ,laboratories ,record1 ,septemb] #aiei1 page #cbc4 ,/ev5 ,m4 ,sp5c]1 8,dial #8,s' = ,satellite10 ,! ,saturday ,ev5+ ,po/1 ,janu>y #ad1 #aifj1 page #ac4 ,space ,electronics ,issue1 ,proce$+s ( ! ,i4,r4,e41 ,april #aifj4 ,william ,meckl+1 8,economic ,pot5tial ( ,communication ,satellites10 ,sci5ce1 ,june #af1 #aifa1 page #ahhe4 ,special ,issue on ,project ,e*o1 ,bell ,sy/em ,te*nical ,j\rnal1 ,july #aifa4 ,c4 ,c4 ,cutl]1 8,radio ,communication by ,means ( ,satellites10 ,planet>y & ,space ,sci5ce ,j\rnal1 ,july #aifa1 page #bed4 ,w4 ,c4 ,jakes1 ,jr41 8,project ,e*o10 ,bell ,laboratories ,record1 ,septemb] #aifa1 page #cjf4 ,john ,r4 ,pi]ce1 8,communication ,satellites10 ,sci5tific ,am]ican1 ,octob] #aifa1 page #ij4 ,unit$ ,/ates ,s5ate1 ,committee on ,a]onautical & ,space ,sci5ces1 ,communication ,satellites3 ,te*nical1 ,economic1 & ,int]national ,developm5ts 7/aff report71 ,u4 ,s4 ,gov]nm5t ,pr9t+ ,(fice1 ,wa%+ton1 #aifb4 ,l4 ,j4 ,c>t]1 editor1 ,communications ,satellites1 ,academic ,press1 ,new ,york & ,london1 #aifb4 8,situation ,report on ,communications ,satellites10 ,int]avia1 ,june #aifb1 page #gdi4 ,leon>d ,jaffe1 8,communications by ,satellite10 ,int]national ,sci5ce & ,te*nology1 ,augu/ #aifb1 page #dd4 8,communicat+ by ,satellite10 ,bus9ess ,week1 ,octob] #bg1 #aifb1 page #hf4 ,project ,tel/> ,r[e ,f9dley1 8,telephone a ,/>10 ,national ,geographic1 ,may #aifb1 page #fch4 ,l\is ,solomon1 ,tel/>1 ,mc,graw-,hill ,book ,company1 ,new ,york1 #aifb4 ,special ,tel/> ,issue1 ,bell ,laboratories ,record1 ,april #aifc4 ,special ,tel/> ,issue1 ,bell ,sy/em ,te*nical ,j\rnal1 ,july #aifc4 ,satellite ,communications ,case ,hi/ories #a4 ,h[ ,d ,we ,calculate a ,satellite's ,orbit8 ,m>io ,iona1 8,satellite ,orbits10 ,! ,physics ,tea*]1 ,may #aifc1 page #ee4 ,a4 ,j4 ,claus et al41 8,orbit ,det]m9ation & ,pr$iction & ,comput] ,programs10 ,bell ,sy/em ,te*nical ,j\rnal1 ,july #aifc1 page #aceg4 #b4 ,:at ,color ,%\ld a ,satellite ,be8 ,p4 ,t4 ,haury1 8,!rmal ,design ( ! ,electronics ,cani/]10 ,bell ,laboratories ,record1 ,april #aifc1 page #afa4 ,j4 ,w4 ,we/1 8,space ,h>dw>e ,aspects ( ! ,satellite10 ,bell ,laboratories ,record1 ,april #aifc1 page #afg4 ,pet] ,hrycak1 et al41 8,! ,spacecraft ,/ructure & ,!rmal ,design ,consid]ations10 ,bell ,sy/em ,te*nical ,j\rnal1 ,july #aifc1 page #igc4 #c4 ,h[ ,d ,we ,make ,optical ,measurem5ts on a ,satellite8 ,w4 ,c4 ,jakes1 ,jr41 8,p>ticipation ( ! ,holmdel ,/ation 9 ,project ,tel/>10 ,bell ,sy/em ,te*nical ,j\rnal1 ,july #aifc1 page #adba4 #d4 ,h[ ,d ,we ,keep ,sol> ,cell ,p[] ,plants ,work+ 9 ,space8 ,d4 ,m4 ,*ap9 et al41 8,! ,bell ,sol> ,batt]y10 ,bell ,laboratories ,record1 ,july #aiee1 page #bda4 ,g4 ,r4 ,fro/1 ,f ,sun to ,s\nd1 ,bell ,telephone ,laboratories1 ,new ,york1 #aifa4f ,f4 ,m4 ,smits1 ,k4 ,d4 ,smi?1 & ,w4 ,l4 ,br[n1 8,sol> ,cells = ,communications ,satellites 9 ! ,van ,all5 ,belt10 ,j\rnal ( ! ,briti% ,i4,r4,e41 ,augu/ #aifa1 page #afa4 ,d4 ,m4 ,*ap91 ,en]gy f ! ,sun1 ,bell ,telephone ,laboratories1 ,new ,york1 #aifb4f ,r4 ,e4 ,d4 ,&]son et al41 8,! ,satellite ,p[] ,sy/em10 ,bell ,laboratories ,record1 ,april #aifc1 page #adb4 ,k4 ,d4 ,smi? et al41 8,! ,sol> ,cells & ,_! ,m\nt+10 ,bell ,sy/em ,te*nical ,j\rnal1 ,july #aifc1 page #agfe4 #e4 ,w\ld ,"t ,delay ,be a ,problem 9 ,us+ a ,syn*ron\s ,satellite8 ,g4 ,m4 ,phillips1 8,e*o & ,its ,effect on ! ,telephone ,us]10 ,bell ,laboratories ,record1 ,augu/ #aied1 page #bha4 ,w4 ,a4 van ,b]geijk1 ,j4 ,r4 ,pi]ce1 & ,e4 ,e4 ,david1 ,jr41 ,waves & ! ,e>1 ,an*or ,books 7,sci5ce ,/udy ,s]ies pap]back71 ,d\bl$ay ,company1 ,new ,york1 #aifj4 ,r4 ,p4 ,havil&1 8,! ,syn*ron\s ,satellite10 9 ,communications ,satellites1 ,l4 ,j4 ,c>t]1 editor1 ,academic ,press1 ,new ,york & ,london1 #aifb1 page #aac4 #f4 ,h[ ,d ,we ,repair an ,orbit+ ,satellite8 ,d4 ,s4 ,peck et al41 8,surface ,effects ( ,radiation on ,transi/ors10 ,bell ,sy/em ,te*nical ,j\rnal1 ,janu>y #aifc1 page #ie4 8,fix+ ,up ,tel/>10 ,"t1 ,janu>y #ah1 #aifc1 page #dh4 ,e4 ,p4 ,moore & ,w4 ,j4 ,mayba*1 8,satellite ,comm& & ,telemetry ,sy/ems10 ,bell ,laboratories ,record1 ,april #aifc1 page #aef4 ,j4 ,s4 ,mayo et al41 8,! ,comm& ,sy/em ,malfunction ( ! ,tel/> ,satellite10 ,bell ,sy/em ,te*nical ,j\rnal1 ,july #aifc1 page #afca4 ,note3 ,! ,bell ,laboratories ,record is publi%$ by ,bell ,telephone ,laboratories1 ,incorporat$1 #dfc ,we/ ,/reet1 ,new ,york #ad1 ,new ,york4 ,! ,bell ,sy/em ,te*nical ,j\rnal is publi%$ by ! ,am]ican ,telephone & ,telegraph ,company1 #aie ,broadway1 ,new ,york #g1 ,new ,york4 ,! ,editor ,ronald ,m4 ,fo/]1 ,jr41 0 born 9 ,pla9field1 ,new ,j]sey1 & receiv$ an ,a4,b4 degree f ,h>v>d ,college 9 #aidh4 ,he jo9$ ,bell ,telephone ,laboratories 9 #aief1 & is a memb] ( ! ,educational ,aids ,dep>tm5t ( ! ,public ,relations & ,publication ,division4 ,he is engag$ 9 developm5t ( mat]ial = ! ,bell ,sy/em ,aid to ,high ,s*ool ,sci5ce ,program4 ,footnotes #a,?is is obta9$ f k g,r1 :]e g is ! accel]ation due to gravity & ,r is ! radius ( ! e>?4 7,"h1 we c use k #if1ejj miles p] second47 #b;,donald ,r4 ,h]riott ( ,bell ,labs _h sugge/$ us+ plane reflectors on satellites z long ago z #aieg--;al?\gh 8 idea 0 t ?is w\ld increase _! visibility1 r ?an aid 9 det]m9+ _! attitude4 #c,?is me?od 0 develop$ by ,d4 ,w4 ,hill ( ,bell ,telephone ,laboratories4 #d,we w n attempt to g into all ! details ( semiconductor physics "h4 ,if y w\ld l to "k m ab\t h[ sol> cells "w1 ref] to ! ,sugge/$ ,read+ on page #hh4 #e,see pages #db & #dc4 #f,publi%$ z "p ( ! ,bell ,sy/em ,aid to ,high ,s*ool ,sci5ce ,program4 ,illu/ration3 ,wrap>\nd cov] image ,transcrib]'s ,notes --,sil5tly correct$ a few typos4 --,modifi$ "s image ref]5ces to reflect ! pageless fl[able e,book =mat4 --,reta9$ publication in=mation f ! pr9t$ edition3 ?is e,book is public-doma9 9 ! c\ntry ( publication4 --,9 ! text v]sions only1 text 9 italics is delimit$ by und]scores4