voyagers 1 and 2 press kit

8/8/2019 Voyagers 1 and 2 Press Kit

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N K A NewsNational Aeronautics andSpace AdministrationWashington. D C 20546AC 202 755-8370

PressKitFor Release 1 2 : 0 NOON, EDTTHURSDAY,August 4, 1977

Project VOYAGERS 1 and 2RELEASE N O : 77-136


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iii

RELEASE NO: 7 7 - 1 3 6

CONTENTS

GENERAL RELEASE............................... 1 - 1 3THE VOYAGER SPACECRAFT ....................... 1 5 - 3 8Structure and Configuration................. 1 6Communications ............................. 2 2Power ...................................... 8Computer Command Subsystem ................. 3 1Attitude Control and Propulsion ............ 3 2Temperature Control ........................ 3 7

MISSION PROFILE .............................. 3 9 - 4 7JUPITER....................................... 4 8 - 5 5SATURN........................................ 5 6 - 6 1PLANETARY ATMOSPHERIC AND SURFACE DATA ....... 6 2 - 6 3COMPARISON TABLE (Chart) ..................... 6 4THE SATELLITES OF SATURN (Chart) ............. 6 6VOYAGER SCIENCE .............................. 6 8 - 8 5Voyager Science Investigations ............. 6 9Cosmic-Ray Investigation ................... 7 1Magnetic Fields Investigation............... 7 2Low-Energy Charged-Particle Investigation... 7 1Infrared Spectroscopy and RadiometryInvestigation ............................. 7 3IRIS Instruments ........................... 7 4Photopolarimetry Investigation.............. 7 5Planetary Radio Astronomy Investigation..... 7 5Plasma Investigation ....................... 6Plasma Wave Investigation .................. 7 8

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R a d i o S c i e n c e I n v e s t i g a t i o n.................. 7 9I m a g in g S c i en ce I n v e s t i g a t i o n ................ 79U l t r a v i o l e t Spec t roscopy I n v e s t i g a t i o n....... 8 2V O Y A G E R S C I E N C E T E A M S .......................... 86-90VOYAGER M I S S I O N H IG H L IG H T S ( C h a r t ) ............. 9 1V O Y A G E R L A U N C H P R E P A R A T I O N S.................... 9 2 - 9 5T Y P I C A L V OY A GE R L AU NC H S E Q U E N C E ................ 9 6 - 1 0 2T R A C K I N G A ND D AT A A C Q U I S I T I O N .................. 103-105M I S S I O N C O N T R O L A N D C O M P U T I N G C E N T E R ........... 106-107VOYAGER TEAM ................................... 108- 111VOYAGER S UBCONTRACTORS......................... 1 1 1 - 1 1 4C O N V E R S I O N T A B L E............................... 11 5


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N/\sANewsN?tionalAeronautics andSpace AdministrationWashington D C 20546AC 202 755-8370

N ic h o la s P a n a g a k o sH e a d q u a r t e r s , W a s h i n g t o n , D. C.(Phone: 2 0 2 / 7 5 5 - 3 6 8 0 )

Fc jr Release1 2 : O O Noon, E D TT H U R S D A Y ,Augus t 4 , 1 9 7 7

Frank B r i s t o wNASA J e t P r o p u l s i o n L a b o r a t o r y , P a s ad e na , C a l i f .(Phone: 2 1 2 / 3 5 4 - 5 0 1 1 )

RELEASE N O : 77-136

TWO VOYAGERS SET F O R LAUNCH

NASA w i l l l a u n c h t w o V oyager s p a c e c r a f t t h i s summer f o ra n e x t e n s i v e r e c o n n a i s s a n c e of t h e o u t e r p l a n e t s .

R i d i n g a t o p a T i t a n C e nt a ur r o c k e t , t h e V oy ag er s w i l lbe launche d f rom Kennedy Space Ce nt e r , F l a . , on a decade-l o ng o dy ss ey t h a t c o u ld t a k e them t o a s many a s 1 5 m a jo rh e a v e n l y b o d i e s .

T he se i n c l u d e g i a n t J u p i t e r an d r i n ge d S a t u r n , s e v e r a lmoons of b o t h p l a n e t s a nd p o s s i b l y U ra nu s.

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M aking me as u re m en ts an d t a k i n g c l o s e u p p i c t u r e s , t h eVoyagers w i l l r e t u r n i n fo r m at i on t h a t c o ul d s he d new l i g h ton t h e o r i g i n a nd e a r l y h i s t o r y o f t h e s o l a r s y s t e m a nd o u rown p l a n e t E a r th .

The f i r s t Vo yag er w i l l be l aunched abou t A ug . 2 0 . Thesecond i s s c h ed u l ed f o r l a u n c h 1 2 d a y s l a t e r , a b o u t S e p t . 1.

Voyager 2 w i l l be l aunched f i r s t and Voyager 1 s e c o n d ,a s Voyager 1 w i l l f l y a f a s t e r t r a j e c t o r y t h a n i t s companionand reach J u p i t e r i n March, 1 9 7 9 , fo u r m onths ahead o fVoyager 2 . A t S a t u r n e n c o u n t e r V oy ag er 1 w i l l be a b o u t n i n emonths ahead of i t s s i s t e r c r a f t .

A t J u p i t e r t h e g r a v i t y - a s s i s t t ec h ni qu e -- u s i n g ap l a n e t ' s g r a v i t a t i o n a l f i e l d t o s p e ed up a s p a c e c r a f t an dchange i t s t r a j e c t o r y -- w i l l be used t o send t h e V oyagerson t o S a t u r n . W it h t h i s " s l i n g s h o t " t e c h n i q u e V oy ag er 1w i l l a r r i v e a t S a t ur n i n l a t e summer of 1 9 8 0 , 3.2 y e a r s a f t e rl au nc h. W it ho ut u s i n g J u p i t e r ' s m as si ve g r a v i t y , t h e f l i g h tf ro m E a r t h wo uld r e q u i r e 6 . 1 years. When it r e a c h e s S a t u r n ,Voyager w i l l h a v e t r a v e l e d 2.2 b i l l i o n k i l o m et e rs ( 1 . 4b i l l i o n m i l e s ) t h r o u g h s p a c e .

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A f t e r co m pl et in g t h e i r p l a n e t a r y m i s s io n s , t h e t w os p a c e c r a f t w i l l c o n t i n u e o u tw a r d fr o m t h e s o l a r sys tem anda c r o s s t h e bo un da ry o f t h e win d o f c h a rg e d p a r t i c l e s ( s o l a rw i n d ) t h a t streams o ut wa rd f ro m t h e S u n, t h u s p e n e t r a t i n gi n t o i n t e r s t e l l a r s p a c e .

T h e V o y a g e r s p a c e c r a f t a r e a d v a n c e d v e r s i o n s of p l a n e -t a r y e x p l o r e r s t h a t ha ve s t u d i e d M e rc ur y, V enus a nd M a r s .The new c r a f t w eigh 825 k i l o g r a m s ( 1 , 8 2 0 pou nds ) . The space -c r a f t d i f f e r f rom t h e i r M ar in er and Vik in g p r e d e ce s s o rs i nmany r e s p e c t s , d ue p r i m a r i l y t o t h e e n vi ro n me n t i n t o w hic ht h e y w i l l v e n t u re a nd t h e g r e a t d i s t a n c e s a c ross w h i c h t h e ym u s t c om m un ic at e w i t h E a r t h . S i n c e t h e a mo un t o f s u n l i g h twhich s t r i k e s t h e o u t e r p l a n e t s i s o n l y a s m a l l f r a c t i o n oft h a t w hi ch r e a c h e s E a r t h , t h e Vo y ag e rs c a n n o t d ep en d ons o l a r e n e rg y b u t m us t u s e n u c l e a r power -- r a d i o i s o t o p et h e r m o e l e c t r i c g e n e r a t o r s . The V o ya g er s a r e dominated byt h e l a r g e s t c om mu ni ca ti on s a n t e n n as y e t f lo wn on p l a n e t a r ym i s s i o n s : 3 . 7 m e t e r s ( 1 2 f e e t ) i n d i am e t er .

The Voyagers a re m o r e a u t o m a t i c a n d i n d e p e n d e n t o fE a rt h- ba se d c o n t r o l t h a n e a r l i e r p l a n e t a r y s p a c e c r a f t . Theg r e a t d i s t a n c e s ac ros s w hic h r a d i o s i g n a l s b et we en E a r t ha nd V oy ag er s m us t t r a v e l an d t h e l o n g l i f e t i m e of t h e m i s s io nr e q u i r e t h a t t h e V oy ag ers be a b l e t o c a r e f o r th e m se l ve s a n dp e rf or m l o n g, d e t a i l e d a nd complex s c i e n t i f i c s u rv e y s w i t h o utco n t in ua l com manding from t h e g round .

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They a r e t h e f i r s t p l a n e t a r y s p a c e c r a f t t o c a r r y ane x p e nd a b le s o l i d - f u e l e d p r o p u l s i o n m odule f o r u s e d u r i n gl au n ch . A f t e r l a u n c h , a 68,000-newton- thrus t (15 ,300-1b. -t h r u s t ) s o l i d - p r o p e l l a n t r o c k e t mo to rs on t h e p r o p u l s io nmodules w i l l p l a c e t h e s p a c e c r a f t on t h e i r f l i g h t p a t h s t oJ u p i t e r .

They w i l l u se s t e e r i n g t h r u s t e r s f o r t r a j e c t o r y correc-t i o n s . Some t r a j e c t o r y c o r r e c t i o n m aneuvers w i l l r e q u i r ee n g i n e b u r n s o f m o r e t h a n a n h o u r -- i n some c a s e s s p r e a do v e r s e v e r a l d ay s.

Each Voyager w i l l u s e 11 i n s t ru m e n t s i n c l u d i n g t h es p a c e c r a f t r a d i o t o s t u d y t h e p l a n e t s , t h e i r s a t e l l i t e s , t h er i n g s o f S a t u r n , t h e m a gn e ti c r e g i o n s s u r r o u nd i n g t h e p l a n e t sa nd i n t e r p l a n e t a r y sp a ce . The i n s t r u m e n t p a y lo a d w ei gh s1 0 5 k g ( 2 3 1 l b . ) .

The Voyagers w i l l c a r r y w i d e -a n g le a n d n a r ro w - a ng l et e l e v i s i o n cameras, cosmic r a y d e t e c t o r s , i n f r a r e d sp e ct ro -meters a nd r a d i o m e t e r s , l ow -e ne rg y c h a r g e d - p a r t i c l e d e t e c t o r s ,m ag ne to m et er s, p h o t o p o l a r i m e t e r s , p l a n e t a r y r a d i o as tr on om yrece ive rs , p la sm a a n d p la sm a wave i n s t r u m e n t s a n d u l t r a v i o l e ts p e c t r o m e t e r s .

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The t e l e v i s i o n cameras w i l l p r ov i de p i c t u r e s of J u p i t e ra nd S a t u r n o f g r e a t e r r e s o l u t i o n t h a n a ny ta k e n f ro m E a r t ho r b y t h e e a r l i e r P i o n e e r 1 0 and 11 q a c e c r a f t . They w i l ls tu d y J u p i t e r f o r e i g h t m o nt hs . The cameras s ho ul d a l s o t a k et h e f i r s t h i gh r e s o l u t i o n , c l os e up p ho to s of t h e G a l i l e a ns a t e l l i t e s of J u p i t e r , t h e m ajo r s a t e l l i t e s o f S a t u r n a ndS a t u r n ' s r in gs .. ( P i o n e e r 11 i s now o n a t r a j e c t o r y w h ic hw i l l t a k e it t hr ou gh S a t u r n ' s r i n g s i n 1 9 7 9 , b u t t h e p i c t u r e st a k e n -- i f any -- w i l l have l e s s r e s o l u t i o n t h a n t h e V oyagerimages by a f a c t o r o f 100.)

The o t h e r V oy ag er i n s t r u m e n t s w i l l s t u d y t h e a t m o s p h e r eof t h e p l a n e t s and t h e i r s a t e l l i t e s , t h e i r m a gn et os ph er e a ndt h e r e l a t i o n s h i p s b e tw ee n t h e s e r e g i o n s a nd t h e s o l a r windt h a t s t reams t h ro u gh i n t e r p l a n e t a r y s p a ce and t h e r a d i o s i g -n a l s f ro m J u p i t e r (w hich e m i t s t h e s t r o n g e s t r a d i o n o i s e i no u r sk y e x c e p t t h e S u n ). O th er o b j e c t i v e s i n c l u d e a l l - s k ys u r v e y s of i n t e r p l a n e t a r y s pa ce a nd g r a v i t a t i o n a l f i e l d s .

An o p t i o n i s b e i n g m a i n t a i n e d t o send Voyager 2 on t ot h e p l a n e t U ra nu s, 2 0 t i m e s f a r t h e r fr om t h e Sun t h a n E a r t h .E n c o u n t e r , w h ic h w ou ld o c c u r i n J a n u a r y 1 9 8 6 , w o u ld p e r m i tt h e f i r s t c l o se u p ex am in at io n of i t s r e c e n t l y d i sc o v e re dr i n g s . The U r an u s o p t i o n w i l l b e e x e r c i s e d o n ly i f p ri m ar yg o a l s of S a t u r n h av e b e e n m e t b y t h e f i r s t V oyag er a nd t h eo p e r a t i n g c o n d i t i o n of t h e s e c o n d V oy ag er w a r r a n t s t h e a d de df o ur -y e ar t r i p . - m o r e -


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The V oy ag er s p a c e c r a f t r e c e i v e a l a r g e i n c r e a s e i nv e l o c i t y a5 a r e s u l t o f t h e i r c l o s e f l y b y o f t h e p l a n e tJ u p i t e r . T h is g r a v i t y - a s s i s t v e l o c i t y i n c r e a s e a l l o w s t h es p a c e c r a f t t o reach S a t u r n i n t h e r e l a t i v e l y s h o r t t i m e o f3.2 t o 4 y e a r s w i t h a l a u n c h v e h i c l e t h a t i s o n l y s l i g h t l yl a r g e r t h a n r e q u i r ed f o r J u p i t e r m i ss io n s.t o s en d a s p a c e c r a f t t o S a t u r n f o l l o w i n g a c lose f l y b y o fJ u p i t e r o c c u r s a pp ro x im a te ly e v e r y 2 0 y e a r s . The o p p o r t u n i t yf o r t h e Ur an us o p t i o n i s t h e r e s u l t o f t h e a li gn m en t o fJ u p i t e r , S a t u r n a nd U ra nu s w hi ch h a pp e ns o n l y o n ce e v e r y4 5 y e a r s .

T h i s o p p o r t u n i t y

P r o j e c t Voyager r e p r e s e n t s t h e n e x t s t e p i n t h e U n it edS t a t e s ' prog ram o f s y s t e m a t i c p l a n e t a r y e x p l o r a t i o n i n wh ic ht h e s o l a r s y s t e m i s used a s a n a t u r a l l a b o r a t o r y . By b e i n ga b l e t o com pare the s i m i l a r i t i e s an d d i f f e r e n c e s o f t h ev a r i o u s p la n e t s , s c i e n t i s t s e xp ec t t o l e a r n more a b o u t t h ep r o ce s se s t h a t a f f e c t t h e E a r th and b e t t e r u n de rs ta nd t h eh i s t o r y of t h e s o l a r sys tem.

U n t i l r e c e n t l y o u r kn owled ge o f J u p i t e r a nd S a t u r n w a so n l y r u d im e n ta r y. G rou nd-b ased s t u d i e s by o p t i c a l i n f r a r e d

a nd r a d i o a st ro no my d e f i n e d t h e m o s t b a s i c p r o p e r t i e s o fJ u p i t e r a nd S a tu r n and t h e i r s a t e l l i t e s a n d h i n t e d a t t h eu ni qu e s c i e n t i f i c p o t e n t i a l of t h e s e s ys te ms .

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I n 1 9 73 an d 1 9 7 4 a f i r s t c lo s e - u pi t s sys tem w a s p r o v i d e d b y t w o P i o n e e r

lo o k a t J u p i t e r ands p a c e c r a f t . A s

P i o n e e r s 1 0 and 11 sp ed p a s t J u p i t e r , t h e i r i n s t r um e n t sbegan t o r e v e a l t h e c o m p le x it y o f i t s a t m o s p h e r e a n d t h ee x t e n t an d s t r e n g t h o f t h e J o v i a n m ag ne to sp he re . V oy ag eri s t h e n e x t l o g i c a l s t e p i n t h e e x p l o r a t io n o f t h e J ov i ansys tem . A l s o , by c a r r y i n g o u t d e t a i l e d e x p l o r a t i o n o fS a t u r n , t h e s e s p a c e c r a f t w i l l p r o v i d e a f a s c i n a t i n g p e rs pe c-t i v e f o r d e t a i l e d c om pa ri so ns o f a h o s t o f u n f a m i l i a r w o r ld s .

J u p i t e r and S a t u rn a re t h e l a r g e s t p l a n e t s . T og et he rw i t h t h e i r many s a t e l l i t e s t h e y d om i na te t h e s o l a r s y s -t e m . The d ia m e t e r o f J u p i t e r i s 1 0 t i m e s t h a t o f E a r t h , a ndit c o n t a i n s more m a t t e r t h a n a l l o f t h e o t h e r p l a n e t s p u tt o g e t h e r . W i t h i t s r e t i n u e o f 1 3 moons, f o u r o f th em a sl a r g e a s p l a n e t s , J u p i t e r i s a c t u a l l y t h e c e n t e r o f a m inia -t u r e s o l a r s y st em l i k e t h e Sun a nd p l a n e t s .

S a t u r n a l s o h a s a sys tem of many s a t e l l i t e s a n d i n c l u d e s ,i n a d d i t i on , t w o u n iq ue f e a t u r e s , a s p e c t a c u l a r r i n g s ys te mw h i c h a p p e a r s t o b e c om posed m a i n l y o f t i n y p i e c e s o f i c eand snow and one l a rge s a t e l l i t e , T i t a n , w i t h a n a tm o sp h er ea s m a s s i v e a s t h a t of t h e E a r t h . I n a ny p ro gr am o f p l a n e t a r ye x p l o r a t i o n s t u d y of t h e J o v i a n an d S a t u r n i a n s y s te m s i s o fp aram ou nt i n t e r e s t f o r u n de rs ta n di ng th e o r i g i n a nd e v o l u t i o no f t h e s o l a r sys tem .

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- 8 -I n s p i t e of t h e i r g r e a t s i z e , J u p i t e r a nd S a t u r n a r e

m y s t e r i o u s worlds . Both a re g i a n t b a l l s o f g a s w i t h n oa p p ar e n t s o l i d s u r f ac e . B o t h a re composed l a r g e l y of hydro-g e n a n d h e l iu m . T h e se p l a n e t s b e s t r e p r e s e n t t h e o r i g i n a lmater ia l s f rom w hich t h e Sun and a l l t h e p l a n e t s -- i n c l u d i n gE a r t h -- w e r e form ed . B oth J u p i t e r a nd S a t u r n c o n s t i t u t em i n a t u r e b u t u n i q u e l y a c c e s s i b l e l a b o r a t o r i e s f o r s t u d y ofphenomenon of w id e- ra ng in g a s t r o p h y s i c a l i n t e r e s t .

L i k e t h e s t a r s , J u p i t e r an d S a t u r n each have t h e i r owni n t e r n a l en er gy s o u rc e s , r a d i a t i n g n e a r ly t w i c e a s muche n e r g y as t h e y receive f r o m t h e Sun. A s P i o n e e r 1 0 and 11m ea su re me nt s r e v e a l e d , J u p i t e r h a s a s t r o n g m a g n e t i c f i e l dand i s s ur ro un de d by r a d i a t i o n b e l t s s i m i l a r t o t h e Van A l l e nb e l t s around t h e Ear th . The v a s t , r a p i d l y s p i n n i n g mag neto -s p he re and r a d i a t i o n b e l t s of J u p i t e r make it a major s o u r c eof severa l t y p e s o f r a d i o r a d i a t i o n .

The atmospheres of these g i a n t p l a n e t s a re d r i v e n byt h e s a m e f o r c e s t h a t a c t o n E a r t h ' s a tm o sp h er e, b u t o n am u c h l a r g e r s ca l e . Major c y c l o n e s , l i k e t h e Gr e a t Red Spotof J u p i t e r , a re t h o u s a n d s of m i l e s ac ros s and p e r s i s t f o rc e n t u r i e s . T h e i r a tm o sp h er es c o n t a i n m u l t i p l e c l ou d l a y e r se ac h w i th t h e i r own t e m p e r a t u r e a n d c h e m i c a l c o m p o s i t i on .

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The f o u r l a r g e s t s a t e l l i t e s o f J u p i t e r , I o , Europa,Ganymede and C a l l i s t o , p r o v i d e a v a r y in g and f a s c i n a t i n gmicrocosm o f u n i q u e w o r l d s .r o c k , some of i c e , s o m e of w a t e r . T h e i r s u r f a c e s p ro b a bl yr a n g e f r o m l u n a r - l i k e c r a t e r e d p l a i n s , t o s a l t -c o v er e d b ed so f e x t i n c t seas , t o e x o t i c l a n d f o r m s c r e a t e d o u t o f i c ean d mud. I n i c e and w a te r -dom ina ted regimes , f a m i l i a r geo-l o g i c p r o c e s s es w i l l t a k e p l a c e t h o u s a n d s o f times f a s t e rt h a n on a r oc k y p l a n e t . T o t a l l y u n f a m i l i a r g e o l o g i c f o r m sa r e e xp e c te d a s w e l l . M o s t s a t e l l i t e s of S a t u r n a r ea p p a r e n t l y a l s o c o m p o s e d p r i m a r i l y of i c e . But T i t a n , t h el a r g e s t s a t e l l i t e i n t h e s o l a r sy ste m, h a s i n a d d i t i o n anatmosphere s i m i l a r i n s i z e t o t h a t o f t h e E a r t h ' s b u t v e ryd i f f e r e n t i n c o m po si ti on .

Some a re co mp osed l a r g e l y o f

S c i e n t i s t s e x p e c t t h a t o r g a n i c m o l e c u l e s a re b e i n gc r e a t e d t o da y i n t h e atmosphere o f T i t a n a nd t h a t t h i ss t r a n g e , c o l d s a t e l l i t e may ev e n p r o v i d e c l u e s t o t h eo r i g i n of l i f e on E a r t h .

T h e t h r e e s p e c t a c u l a r r i n g s t h a t s u r r o u n d S a t u r n may bet h e r e m a i n s of a s a t e l l i t e t h a t came to o c l o s e a nd w a s brokenup by t h e s t r o n g t i d a l f o r c e s of t h e p l a n e t o r th e y may beremnants of m a t e r i a l from t h e b i r t h of t h e s o l a r sys temt h a t n ev e r c o a le s c e d t o f orm a l a r g e moon.

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J u p i t e r o r b i t s t h e S u n a t a d i s t a n c e of 7 78 m i l l i o nkm (483 m i l l i o n m i . ) . One J u p i t e r y e a r e q u a l s 1 1 .8 6 E a r t hy e ar s . J u p i t e r ' s day i s l e s s t h a n 1 0 h o u r s l o n g .

S a tu r n o r b i t s t h e Sun a t a d i s t a n c e of 1 . 4 2 b i l l i o n km( 88 3 m i l l i o n m i . ) . I t c o mp le te s o ne o r b i t e v e r y 2 9 . 4 6 E a r t hy e a r s . A d a y o n S a t u r n i s 1 0 h o u r s a n d 14 m inutes long .The w i de s t v i s i b l e r i n g of S a t u r n h a s a r a d i u s o f 1 3 6 ,0 0 0km (84 ,500 m i . ) .

C l o s e s t a p p r o a c h t o J u p i t e r -- March 5 , 1979 -- w i l lbe abou t 278 , 000 k m (173,000 m i . ) from t h e v i s i b l e c lo u ds u r f a c e o f t h e p l a n e t . B oth E a r t h a nd Sun w i l l d i s a p p e a rb eh in d J u p i t e r , a s s e e n f r o m t h e s p a c e c r a f t ( o c c u l t a t i o n ) ,a l l o w i n g s c i e n t i s t s t o make new measurements of t h e s t r u c t u r ea nd c o m po s i t io n o f t h e p l a n e t ' s u p p er a t m os p h er e fr om atmos-p h e r i c e f f e c t s on V oy ag er ' s r a d i o s i g n a l s a s t h e y p a s st h r o u g h t h e J o v i a n a t mo s ph e re e n r o u t e t o E a r t h .

A f t e r p a s s i n g J u p i t e r , Voyager 1 w i l l e xa min e a l l f o u rof t h e l a r g e G a l i l e an s a t e l l i t e s . O b s er v at io n s o f J u p i t e rw i l l c o n ti n ue f o r a m o n t h a f t e r c l o s e s t a pp ro ac h, u n t i l e a r l yA p r i l 1979 .

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Voyager 2 w i l l b e g i n i t s o b s e r v a t o r y p h a s e of J u p i t e rabout two weeks l a t e r , 8 0 d a y s b e f o r e c l o s e s t a p pr oa ch a sd i d V o y a g e r 1. I t w i l l o bs er ve f o ur s a t e l l i t e s d u r i n g t h ei n b o u n d l e g : C a l l i s t o , Ganymede, Eu rop a and Ama lthea .

T h e s p a c e c r a f t w i l l make i t s c l o s e s t a p p r o a c h t o J u p i t e ro n J u l y 1 0 , 1 9 7 9. F o l l o w i n g a more d i s t a n t c ou r se t ha n i t sp r e d e c e s s o r , t h e s e co n d V oy ag er w i l l p a s s more t h a n t w i c e asf a r f ro m t h e p l a n e t , 6 43 ,0 00 km ( 4 0 0 , 0 0 0 m i . ) away. The secondJ u p i t e r en c ou n te r w i l l c o n t i n u e i n t o A ug ust .

The f i r s t S a tu r n e n c o un t e r w i l l b e g i n i n August 1980and w i l l c o n t i n u e t h r o u g h December. On th e inbound l e g ,Voyager 1 w i l l p a s s w i t h i n 4 , 0 0 0 km (2 ,500 m i . ) o f t h e ma jo rs a t e l l i t e T i t a n . C l o s e s t a p p r o a c h to S a t u r n -- 13 8, 00 0 km(85,800 m i . ) -- w i l l occur Nov. 1 2 , 1 98 0. T i t a n , S a t u r n a ndt h e r i n g s w i l l a l l b l o c k o u t t h e Sun an d E a r t h a s s e e n b yi n s t r u m e nt s on t h e s p a c e c r a f t t o p r ov id e o c c u l t a t i o nm easurem ent s .

S ec on d S a t u r n e n c o u n t e r w i l l b e g in i n J u ne 1 9 8 1 .C l o s e s t a p p r o a c h w i l l occur Aug. 2 7 , 1 9 8 1 . Voyager 2 w i l lo bs er v e t h e s a t e l l i t e s T i t a n , Rhea and Te thys on i t s i nboundj o u r n e y a n d E n c e l a d u s a t c l o se s t approach . Encoun te r w i l lc o n t i n u e t h r o u g h S e p t e m b e r .

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Tracking and data acquisition will be performed bythe Deep Space Network (DSN) with stations in California,Australia and Spain. At planet encounter, high-rate data

will be received through the DSN's 64-m (210-ft.) antennasubnet. Maximum data rate at Jupiter will be 115,000 bitsper second, at Saturn 44,800.

NASA's Office of Space Science has assigned Voyagerproject management to the Jet Propulsion Laboratory (JPL),Pasadena, Calif., which is managed for NASA by the CaliforniaInstitute of Technology. NASA program manager is RodneyMills and the JPL project manager is John Casani. Dr. MiltonA. Mitz is NASA program scientist and Dr. Edward C. Stone ofCaltech is project scientist.

JPL designed, assembled and tested the Voyager spacecraft.

Voyager's solid rocket motor is provided by the NASAGoddard Space Flight Center's Delta Office. Prime contractoris Thiokol Chemical Corp.

Launch vehicle responsibility has been assigned toNASA's Lewis Research Center, Cleveland, Ohio. Prime con-tractors to Lewis are Martin Marietta Corp., Denver, Colo.,(the Titan) and General Dynamics/Convair, San Diego, Calif.,(the Centaur)

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-13-Tracking, communications and mission operations are

conducted by JPL, which operates the Deep Space Network forNASA's Office of Tracking and Data Acquisition.

The spacecraft's radioisotope thermoelectric qeneratorsare provided to NASA by the U.S. Energy Research and Develop-ment Administration (ERDA). Prime contractor to ERDA isGeneral Electric Co., Valley Forge, Pa.

Estimated cost of the Voyager project, exclusive oflaunch vehicles, tracking and data acquisition and flightsupport activities is $320 million.

(END OF GENERAL RELEASE. BACKGROUND INFORMATION FOLLOWS.

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THE VOYAGER SPACECRAFT

The two Voyager spacecraft are designed tooperate at distances from Earth and the Sun greaterthan those of any previous mission. Communicationscapability, hardware reliability, navigation and tem-perature control are among the major challenges. Thespacecraft are identical. Each can meet the objectivesof either mission and their various options.

Each Voyager consists of a mission module -- theplanetary vehicle -- and a propulsion module, whichprovides the final energy increment necessary to injectthe mission module into the Jupiter transfer trajec-tory. The propulsion module is jettisoned withinminutes after the required volocity is attained. (Forpurposes of mission description, "spacecraft" and"mission module'' will be used interchangeably. Indescribing the prelaunch configuration and launchphase, "spacecraft" will refer to the combined "mis-sion module'' and "propulsion module. )

The mission module after injection weighs 8 2 5 kg( 1 , 8 2 0 lbs.), including a 105 kg (231 lb.) science in-strument payload. The propulsion module, with itslarge solid propellant rocket motor, weighs 1,220 kSr(2,690 lbs.). The spacecraft adaptor joins the space-craft with the Centaur stage of the launch vehicle.It weighs 47.2 kg (104 lbs.) Total launch weightof the spacecraft is 2,100 kg (4,630 lbs.).

To assure proper operation for the four-yearflight to Saturn, and perhaps well beyond, missionmodule subsystems have been designed with high re-liability and extensive redundancy.

and the Viking Mars Orbiters, the Voyagers are sta-bilized on three axes using the Sun and a star (Canopus)as celestial reference points.

Three engineering subsystems are programmable foron-board control of spacecraft functions. (only tra-jectory correction maneuvers must be enabled by groundcommand.)subsystems (CCS), the flight data subsystem ( F D S ) andthe attitude and articulation control subsystem (AACS).

Like the Mariners that explored the inner planets

These subsystems are the computer command

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The memories of these units can be updated ormodified by ground command at any time.Hot gas jets provide thrust for attitude sta-

bilization as well as for trajectory correction man-euver .A nuclear power source -- three radioisotopethermoelectric generators -- provides the spacecraftelectrical power.The science instruments required to view the planetsand their moons are mounted on a two-axis scan platformat the end of the science boom for precise pointing.Other body-fixed and boom-mounted instruments arealigned for proper interpretation of their measure-ments.Data storage capacity on the spacecraft is about5 3 6 million bits of information -- the equivalent ofabout 100 full-resolution photos.Dual frequency communication links -- S-band andX-band -- provide accurate navigation data and largeamounts of science information during planetary en-counter periods (up to 115,200 bits per second at

Jupiter and 44,800 bps at Saturn).Dominant feature of the spacecraft is the 3.66-

meter (12-foot) diameter high-gain antenna which willpoint toward Earth continually after the initial 80days of flight.

While the high-gair, antenna dish is white, mostvisible parts of the spacecraft are black -- blanketedor wrapped for thermal control and micrometeoroid pro-tection. A few small areas are finished in gold foilor have polished aluminum surfaces.Structure and Configuration

The basic mission module structure is a 29.5 kg(65 1b.I 10-sided aluminum framework with 10 elec-tronics packaging compartments. The structure is4 7 centimeters (18.5 inches) high and 1.78m (5.8 ft.)across from side to side. The electronics assembliesare structural elements of the 10-sided box.- more -


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The spherical propellant tank, which suppliesfuel to hydrazine thrusters for attitude control andtrajectory correction maneuvers (TCM), occupies the centercavity of the decagon.drazine to 12 small attitude control and four TCMthrusters on the mission module and to larger thrustvector control engines on the propulsion module.The 3.66 m (12 ft.) diameter high-gain parabolicreflector is supported above the basic structure by atubular trusswork. The antenna reflector has an alu-minum honeycomb core and is surfaced on both sides bygraphite epoxy laminate skins. Attachment to thetrusses is along a 1.78 m (70 inch) diameter supportring. The Sun sensor protrudes through a cutout inthe antenna dish. An X-band feed horn is at thecenter of the reflector. Two S-band feed horns are

mounted back-to-back with the X-band sub-reflector,transparent at S-band, to the high-gain dish. Theother functions as the low-gain antenna.

Propellant lines carry hy-

Louver assemblies for temperature control arefastened to the outer faces of four of the electronicscompartments. Top and bottom of the 10-sided struc-ture are enclosed with multi-layer thermal blankets.Two Canopus star tracker units are mounted side-by-side and parallel atop the upper ring of the decagon.Three radioisoptope thermoelectric generators are

assembled in tandem on a deployable boom hinged on anoutrigger arrangement of struts attached to the basicstructure. The RTG boom is constructed of steel andtitanium. Each unit, contained in a beryllium outercase, 40.6 cm(16 in.) in diameter, 50.8 cm (20 in.)long and weighs 39 kg (86 lb.).The science boom, supporting the instruments mostsensitive to radiation, is located 180 degrees from theRTG boom and is hinged to a truss extending out fromthe decagon and behind the high-gain antenna. The

boom, 2.3 IT. ( 7 1/2 ft.) long, is a bridgework of gra-phite epoxy tubing. Attached on opposite sides of theboom at its mid-point are the cosmic ray and low-energy charged particle instruments. Farther out onthe boom is the plasma science instrument.

The two-axis scan platform is mounted at the endof the boom and provides precision pointing for fourremote-sensing instruments -- the ultraviolet spec-trometer, infrared spectrometer and radiometer,- more -


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VOYAGER RADIOISOTOPETHERMOELECTRIC GENERATOR

END ENCLOSURE

BERY LLlUMOUTER CASEGAS/MANAGEMENTASSEMBLYSi Ge/NICOUPLECOUPLE/TTACHMENTBOLT

BERYLLIUM END DOME

PRESSURE RELIEFDEVICE

RIB/FIN

-CONVERTER

LMO/ASTROQMULTI-FOIL INSULATION


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photopolarimeter and a two-camera im-aging science sub-system.(236 lb.).

Total platform gimballed weight is 107 kg

With both the RTG and science booms deployed, thenearest boom-mounted instrument to a radiation sourceis 4.9 m (16 ft.), with the bulk of the spacecraft be-tween the two. The closest platform-mounted instrument6 . 7 m (21 ft.) away.A polarimetric calibration target, called abrewster plate, is mounted atop the mission modulestructure and aligned so that the photopolarimeterviews the target during science maneuvers planned forthe planetary phases of the mission.A Pair of 1 0 m (3 3 ft.) whip antennas are depl?yedfrom a position external to the top ring of the basic

structure and looking "down" between the RTG boom out-rigger members. The antennas, which form a right angle,are part of the planetary radio astronomy (PRA) in-strument package and are shared with another instrument,the plasma wave science unit (PWS). The PRA and PWSassemblies are body-mounted adjacently. The antennas,beryllium copper tubing, are rolled flat in theirhousing prior to deployment by small electric motors.The magnetic fields investigation experiment con-sists of an electronics subassembly located in one ofthe mission module electronics bays and four magne-tometers -- two high-field sensors affixed to the

spacecraft and two low-field sensors mounted on a13m ( 4 3 ft.) deployable boom. The boom, constructedof epoxy glass, spirals from its stowed position withinan aluminum cylinder and forms a rigid triangular mastwith one magnetometer attached to its end plate andanother positioned 6 nl (20 ft.1 closer to the -space-craft. The mast itself weighs only 2 . 3 kg (5 lbs.),less than the cabling running its length and carryingpower to and data from the magnetometers. The boomhousing is a 23 cm ( 9 in-) diameter cylinder, 66 cm(26 in.) long, supported by the RTG outrigger. Themast uncoils in helix fashion along a line betweenthe rear face of the high-gain antenna and the RTGboom.

Basic structure of the propulsion module is a44 kg ( 9 7 lb.) aluminum semi-monocoque shell.

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The cylinder 1 m (39 in.) in diameter and 0.9 m(35 in.) long, is suspended below the mission modulestructure by an eight-member tubular truss adapter.The hollow of the structure contains the solid rocketmotor which delivers the final owered sta e of flight.The rocket, which weighs 1,220 ig (2,690 l%.) includinc;1,060 kg (2,340 lb.) of propellant, develops an average68,000 N (15,300 lb.) thrust during its 43-second burn.

Mounted on outriggers from the structure areeight hydrazine engines to provide attitude controlduring the solid motor burn and prior to propulsionmodule separation and jettison. Hydrazine fuel issupplied from the missionmodule.

A pair of batteries and a remote driver module f o rpowering the valve drivers to the thrust vector controlengines are positioned on the outer face of the cylin-drical propulsion module structure.

A 0 . 3 7 sq. m (4 Sq. ft.) shunt radiator-sciencecalibration target faces outward from the propulsionmodule truss adapter toward the scan platform. Thedual-purpose structure is a flat sandwich of twoaluminum radiating surfaces lining a honeycomb core.Through an arrangement of power collectors and emitterresistors between the plates, any portion of the elec-trical power from the RTGs c m e radiated to space asheat. The outer surface also serves as a photometriccalibration target for the remote sensing scienceinstruments on the scan platform.

The shunt radiator, as well as the propulsionmodule truss adapter, remain part of the mission modulewhen the propulsion module is jettisoned.Steel alloy-gold foil plume deflectors extendfrom the propulsion module structure to shield thestowed RTGs and scan platform from rocket exhaust duringengine firing.The spacecraft adapter, an aluminum truncated cone,joins the propulsion module with the Centaur stage ofthe launch vehicle. The adapter, 0.71 m (30 in.) tall,

1.6 m (63 in.) in diameter at the base (Centaur at-tachment), 1.0 m ( 3 9 in.) at the spacecraft separationjoint and weighs 4 7 . 2 kg (104 lb.). The adapter remainswith the Centaur rocket stage.

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Launch ConfigurationSome mechanical elements of the spacecraft must be

rigidly restrained during the severelaunch vibrationenvironment. Following the launch 2hase appendageswhich were latched securely within the Centaur stagenose fairing are deployed to their cruise positions.The spacecraft pyrotechnic subsystem providessimple and positive deployment with explosive squibs.Devices stowed securely during launch and released fordeployment by the pyrotechnic system are the scienceboom, RTG boom and magnetometer boom.The pyrotechnic subsystem also routes power todevices to separate the spacecraft from the launch

vehicle, activates the propulsion module batteries,ignites the solid propellant rocket motor, seals offthe propellant line carrying hydrazine from themission module to the propulsion module, jettisonsthe propulsion module and releases the Infrared Radi-ometer and ,Interfermeter pectrometer insrument-s dustcover.Communications

Communications with the Voyager spacecraft willbe by radio link between Earth tracking stations and adual frequency radio system aboard the spacecraft.

The "uplink" operates at S-band, carrying com-mands and ranging signals from ground stations to oneof a pair of redundant receivers. The "downlink" istransmitted from the spacecraft at S-band and X-bandfrequencies.

a programmable flight data subsystem ( F D S ) , modulationdemodulation subsystem (MDS), data storage sub-system (DsS) and high gain and low qain antennas.trols the science instruments and formats all scienceand engineering data for telemetering to Earth. Thetelemetry modulation unit (TMU) of the MDS feeds datato the downlink. The flight command unit of the MDSroutes ground commands received by the spacecraft.

The onboard communications system also includes

The FDS, one of the three onboard computers, con-

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Only one receiver will be powered at any onetime with the redundant receiver at standby. Thereceiver will operate continuously during themission at about 2113 MHz. Different frequencyranges have been assigned to the radio frequency sub-systems of each spacecraft. The receiver can be usedwith either the high gain or low gain antenna.

The S-band transmitter consists of two redundantexciters and two redundant RF power amplifiers ofwhich any combination is possible. Only one ex-citer-amplifier combination will operate at any onetime. Selection of the combanation will be by onboardfailure detection logic within the computer commandsubsytem ( C C S ) , with ground command backup. The samearrangement of exciter-amplifier combinations makesup the X-band transmitting unit.

One S-band and both X-band amplifiers employtraveling wave tubes (TWT). The second S-band unitis a solid-state amplifier. The S-band transmitteris capable of operating at 9.4 watts or at 28.3 wattswhen switched to high power and can radiate from bothantennas. X-band power output is 12 watts and 21.3watts. X-band uses only the high gain antenna. (S-band andX-band will never operate at high power simultaneously).

When no uplink signal is being received, thetransmitted S-band frequency of about 2 2 9 5 MHz andX-band frequency of 8418 M H z originate in the S-bandexciter's auxiliary oscillator or in a separate ultrastable oscillator (one-way tracking.) With thereceiver phase-locked to an uplink signal, the re-ceiver provides the frequency source for both trans-mitters (two-way tracking). The radio system can alsooperate with the receiver locked to an uplink signalwhile the downlink carrier frequencies are determinedby the onboard oscillators (two-way noncoherenttracking).

At present, only the 64-m (210-ft.) antennastations of the Deep Space Network can receive thedownlink X-band signal. Both the 64-m and the 26-m(85-ft.) antenna stations are capable of receiving atS-band.The X-band downlink will not be in use duringabout the first 80 days of the mission -- until theEarth is within the beam of the spacecraft's hiqh gainantenna.

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Communications during launch, near-Earth and earlycruise phase operations will be confined to S-band andthe low gain antenna. An exception occurs during thefirst week of flight when the spacecraft, on inertialcontrol, points the high gain antenna toward Earth tosupport instrument calibration and an optical navigationhigh-rate telecommunications link test.

The high gain antenna, with a 3.66-m-diameter(12 ft.) parabolic reflector, provides a highly direc-tional beam. The low gain antenna provides essentiallyuniform coverage in the direction of Earth.Under normal conditions after the first 80 daysof the mission, all communications -- both S-band andX-band -- are via the high gain antenna. X-band isturned off, however, and the S-band transmitter and re-ceiver are switched to the low gain antenna during

periodic science maneuvers and trajectory correctionmaneuvers.The S-band downlink is always on, operating at highpower during maneuvers or during the cruise phase only

when the 26 m ( 8 5 ft.) antenna DSN stations are trackinglow power whenever X-band is on. At Saturn, both S-bandand X-band transmitters will be at low power when gyrosand tape recorder are on simultaneously.Commanding the Spacecraft

Ground commands are used to put into execution se-lected flight sequences or to cope with unexpected events.Commands can be issued in either a predetermined timedsequence via onboard program control or directly as re-ceived from the ground. Most commands will be issued bythe spacecraft's computer command subsystem (CCS) in itsrole as "sequencer of events" and by the flight datasubsystem (FDS) as controller of the science instruments.All communications between spacecraft and Earth willbe in digital form. Command signals, transmitted at 16bits per second (bps) to the spacecraft, will be detectedin the flight command unit and routed to the CCS for fur-ther routing to their proper destination. Ground com-mands to the spacecraft fall into two major categories:

discrete comands and coded commands.

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A discrete command causes a single action on thespacecraft. For example, DC-2D switches the S-bandamplifier to high power: DC-2DR, S-band amplifier lowpower; DC-2E, S-band radiates from high gain antenna:DC-2ER, S-band transmits low gain. Coded commands arethe transfer of digital data from the computer commandsystem or from the ground via the C C S to user subsystems.Subsystems receiving coded commands are flight data, at-titude and articulation control, modulation-demodulation,data storage and power.Ground commands back up all critical spacecraftfunctions which, in a standard mission, are initiatedautomatically by onboard logic. Command modulation willbe off during science maneuvers and trajectory correctionmaneuvers unless a spacecraft emergency arises.

Downlink TelemetryData telemetered from the spacecraft will consistof engineering and science measurements prepared fortransmission by the flight data subsystem, telemetrymodulation unit and data storage subsystem. The encodedinformation will indicate voltages, pressures, tem-peratures, television pictures and other valuesmeasured by the spacecraft telemetry sensors and scienceinstruments.Two telemetry channels -- low rate and high rate --

are provided for the transmission of spacecraft data.The low rate channel functions only at S-band at a s i n o l e40 bits per second data rate and contains real time en-gineering data exclusively. It is on only duringplanetary encounters when the high rate channel isoperating at X-band.The high rate channel is on throughout the mission,operates at either S-band or X-band and contains thefollowing types of data:

Engineering only at 40 bps or1,200 bps (the rate usuallyoccurs only during launch andtrajectory correction maneuvers)transmitted at S-band only.

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0 R e a l - t i m e c r u i s e s c i e n c e ande n g i n e e r i n g a t 2 , 560 , 1 , 2 8 0 , 6 4 0 ,320, 160 and 80 b . p . s . ( 4 0 , 20and 1 0 bps may be used f o rp o s t- S a tu r n o p e r a t i o n s ) t r a n s -m i t t e d a t S-band only .

0 R e a l time e n c o u n t e r g e n e r a ls c i e n c e a nd e n g i n e e r i n g a t 7 . 2k i l o b i t s p e r second (a s p e c i a l115.2 kbps r a t e w i l l bea v a i l a b l e f o r b r i e f p e r i o d s a tJ u p i t e r f o r t h e p la n e t a ry r a d i oas t ronom y and p lasm a w ave ins t ru -m e n t s ) t r a n s m i t t e d a t X-band only,0 R e a l time e n c o u n t e r g e n e r a ls c i e n c e , e n g i n e e r i n g an d t e l e -v i s i o n a t 1 1 5 . 2 , 8 9 . 6 , 6 7 . 2 ,4 4 . 8 , 2 9 . 9 , and 1 9 . 2 kbpst r a n s m i t t e d a t X-band only.0 R e a l time e n c o u n t e r g e n e r a l s c i -e n ce and e n g i n e e r i n g , p l u s t a p er e c o r d e r pl a y ba c k , a t 6 7 . 2 , 4 4 . 8and 2 9 . 9 k b p s t r a n s m i t t e d a tX-band only.0 P l a y b ac k r e c o rd e d d a t a o n l y a t21.6 and 7 . 2 kbps t r a n s m i t t e da t X-band only.0 Memory d a t a s to red i n t h e t h r e eonboard com pute r s -- CCS, FDS andAACS -- r e a d o u t an d p la y e d b ac ka t 40 o r 1 , 2 0 0 b p s t r a n s m i t t e da t e i t h e r S -ba nd o r X-band

( t r e a t e d a s e n g i n e e r i n s d a t a ) .The numerous da ta r a t e s f o r e ac h t y p e of t e l e m e t e r e di n f o r m a t i o n a r e r e q u i r e d b y t h e c h an g in g l e n g t h of t h e

t e le c o mm u n ic a ti o n s l i n k w i t h E a r t h a nd t h e p o s s i b l e ad-v e r s e e f f e c t s of E a r t h w e a t h e r u po n r e c e p t i o n o f X-bandr a d i o s i g n a l s . The S-band c r u i s e s c i e n c e p r im a r y t e l e -m e t r y r a t e i s 2.560 bgS.i n s t r u m e n t s a m p li n g an d w i l l be used o n l y when t h e t e l e -c om m un ic at io ns l i n k c a n n o t s u p p o r t t h e h i g h e r r a t e .

Lesser r a t e s r e s u l t i n r ed u ce d

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I n o r d e r t o a l low r e a l t i m e t r a n s m i s s i o n of v i d e oi n f o r m a t i o n a t e ac h e nc o u n te r , t h e f l i g h t d a t a s u bs ys te mw i l l h a n d le t h e i m ag in g d a t a a t s i x dow nl ink r a t e s from1 1 5 .2 t o 1 9 . 2 kbps . The 115 . 2 -kbps r a t e r e D r e s e n t st h e s t a nd ar d f u l l f r a m e r e a d o u t a t 48 s e c o n d sp e r f r a m e ) o f t h e TV v i d i c o n . U nd er n or ma l c o n d i t i o n s ,t h i s r a t e w i l l b e u s e d a t J u p i t e r . F u l l f r a me , f u l lr e s o l u t i o n TV f ro m S a t u r n ca n be o b t a i n e d by i n c r e a s i n gt h e f ra me r e a d o u t time t o 144 s e c o n d s ( 3 : l s l o w s c a n )and t r a n s m i t t i n g t h e d a t a a t 44.8 kbps a numberof o t h e r s l o w s c a n and f ra me e d i t o p t i o n s a r e a v a i l a b l et o match t h e c a p a b i l i t y of t h e te l e co m m u n ic a ti o n s l i n k .

The d a t a s t o r a g e s u bs y st em c a n r e c o r d a t t w or a t e s : TV p i c t u r e s , g e n e r a l s c i e n c e and e n g i n e er i n g a t1 1 5 . 2 k bp s; g e n e r a l s c i e n c e a nd e n s i n e e r i n g o n l y a t7 . 2 k b p s ( e n g i n e e r i n g i s a c qu i r ed a t o n l y 1 , 2 0 0b . p . s . , b u t i s f or m at te d w i t h f i l l e r t o ma tc h t h e re -c o r d e r i n p u t r a t e ) . The t a p e t r a n s p o r t i s b e l t d r iv e n .I t s 1 / 2 - i n c h m a g n e t i c t a p e i s 328x11 ( 1,0 75 f t . )l o n g a n d i s d i v id e d i n t o e i g h t t r a c k s which a r e r e c o r d e ds e q u e n t i a l l y o ne t r a c k a t a t i m e . T o t a l r e c y c l e a b l es t o r a g e c a p a c i t y i s a b o u t 536 m i l l i o n b i t s -- t h e e-q u i v a l e n t o f 1 0 0 TV p i c t u r e s . P la yb ac k i s a t f o u rs p e e d s -- 57 . 6 , 3 3 . 6 , 2 1 . 6 a n d 7 . 2 k b p s .T r ac k in g t h e S p a c e c r a f t

To a c h i e v e t h e d e s i r e d ma neu ve r a nd f l y b y ac-c u r a c i e s f o r a m u l t i - p l a n e t / s a t e l l i t e e nc ou n t er m i s s i o n ,v e r y p r e c i s e n a v i g a t io n i s r e q u i r e d .T o p r o v i d e t h e s t a n d a r d D op pl er t r a c k i n g d a t a ,t h e S-band s i g n a l t r a n s m i t t e d f ro m E a r t h i s r e c e i v e d a tt h e s p a c e c r a f t , c ha ng ed i n f re q u en c y by a known r a t i oan d r e t r a n s m i t t e d t o E a r t h . It i s p o s s i b l e t o p r e -c i s e l y d e te r m in e t h e t r a n s m i t t e d d ow nli nk f r e q u en c yw h i l e m e as u ri ng t h e D op ple r s h i f t e d r e c e i v e d s i g n a l ,t h e r e b y m e as ur in g s p a c e c r a f t v e l o c i t y . T h i s i s c a l l e dco he re n t two-way t r a ck in g . One-way t r a c k i n g i s when nou p l in k s i g n a l i s r e c e i v e d a nd t h e d o wn li n k c a r r i e r f r e -

quency i s p r o v i d e d b y an onboard o s c i l l a t o r . N oncoheren ttwo-way t racking occurs w hen up l ink and dow nl ink c a r r i e r sa r e o p e r a t i n g i n d ep e n d en t ly .

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(When both S-band and X-band transmitters are on,X-band frequency will always be 11/3 times the S-bandfrequency regardless of the frequency source -- space-craft receiver, ultra stable oscillator or S-bandexciter auxiliary oscillator.)

Distance or range to the spacecraft is measuredin the coherent two-way configuration by transmittinga digital code (ranging modulation) on the uplink,turning this code around in the spacecraft and sendingit back to the ground. By measuring the total elapsedtime between transmitting and receiving the code at theground station and knowing such factors as the speedof light, turnaround delay and relative velocities ofthe spacecraft and tracking station, it is possible todetermine spacecraft range.

Dual frequency ranging (both $-band and X-bandranging on) will be conducted during planetary opera-tions phasrJs of the mission and during the cruisephases when the Deep Space Network's 64-m (21n-ft. antennas are trackinq. Special three-Waysdual-frequency ranging cycles will be conducted while twoor more ground stations on two continents aretracking the spacecraft.All ranging modulation is turned off during

science maneuvers, trajectory correction maneuversand planetary occultations.

Power

The Voyager power subsystem supplies all elec-trical power to the spacecraft by generating, converting,conditioning and switching the power.Power source for the mission module is an array

of three radioisotope thermoelectic generators (RTGs),developed by the U.S. Energy Research and DevelopmentAdministration (ERDA). The propulsion module, activeonly during the brief injection phase of the mission,uses a separate battery source.

The RTG units, mounted in tandem on a deployableboom and connected in parallel, convert to electricitythe heat released by the isotopic decay of Plutonium-238.

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Each isotope heat source has a capacity of 2 4 0 0thermal watts with a resultant maximum electricalpower output of 160 watts at the beginning of the mis-sion. There is a gradual decrease in power output.The minimum total power available from the threeRTGs ranges from about 423 watts within a few hoursafter launch to 384 watts after the spacecraft passesSaturn.

Spacecraft power requirements from launch to post-Saturn operations are characterized by this generalpower timeline: launch and post-launch, 235 to 265watts; interplanetary cruise, 3 2 0 to 365 watts; Ju-piter encounter, 384 to 401 watts; Saturn encounter,377 to 382 watts; and post-Saturn, less than 365watts.Telemetry measurements have been selected to pro-

vide the necessary information for power managementby ground command, if needed.The RTGs will reach full power about six toeight hours after launch. During prelaunch opera-tions and until about one minute after liftoff, thegenerator interiors are kept filled with an inertgas to prevent oxidation of its hot components.Venting the generators to space vacuum is achievedwith a pressure relief device actuated when the out-side ambient pressure drops below 10 psia.Power from the R T G s is held at a constant 30

volts d.c. by a shunt regulator. The 3 0 volts is sup-plied directly to some spacecraft users and isswitched to others in the power distributionsubassembly. The main power inverter also is suppliedthe 30 volts d.c. for conversion to 2.4 kHz square waveused by most spacecraft subsystems. Again, the a.c.power may be supplied directly to users or can beswitched on or off by power relays.Command actuated relays control the distributionof power in the spacecraft. Some relays function assimple on-off switches and others transfer powerfrom one module to another within a subsystem.Among the users of d.c. power, in addition tothe inverter, are the radio subsystem, gyros, pro-pulsion isolation valves, some science instruments,most temperature control heaters and the motors which

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Other elelnents of the Spacecraft use the 2 . 4kHz power.There are two identical 2.4 kHz power inverters --main and standby. The main inverter is on from launchand remains on throughout the mission. In case ofa malfunction or failure in the main inverter, thepower chain, after a 1.5-second delay is switchedautomatically to the standby inverter. Once the switch-over is made, it is irreversible.A 4.8 kHz sync and timing signal from the flightdata subsystem is used as a frequency reference in theinverter. The frequency is divided by two and theoutput is 2 . 4 kHz plus-or-minus 0.002 per cent. Thistiming signal is sent, in turn, to the computer commandsubsystem which contains the spacecraft's master clock.Because of the long mission lifetime, chargedcapacitor energy storage bank are used instead ofbatteries to supply the short term extra power de-manded by instantaneous overloads which would causethe main d.c. power voltage to dip below acceptablelimits. A typical heavy transient overload occursat turn-on of a radio power amplifier.Full output of the RTGs, a constant power source,must be used or dissipated in some way to preventoverheating of the generator units or d.c. voltagerising above allowed maximum. This is controlled bya shunt regulator which dumps excess RTG output powerabove that required to operate the spacecraft. Theexcess power is dissipated in resistors in a shuntradiator mounted outside the spacecraft and radiatedinto space as heat.Two batteries independently supply unrequlatedd.c. power to a remote driver module (RDM) for power-ing valve drivers to the thrust vector control engineson the propulsion module during the injection phaseof the mission. The batteries and the RDM are locatedin the propulsion module which is jettisoned a fewminutes after the mission module is injected onto a

Jupiter transfer trajectory. Each battery is composedof 22 silver oxide-zinc cells with a capacity of 1200ampere seconds at 2 8 to 4 0 volts, depending upon theload.

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B a s i c r e qu i re m e nt o n t h e b a t t e r i e s i s high powerW i t h a l i f e t i m e o f o n l yo r a s h o r t p er i o d -- 1 2 m i n u t e s .6 6 m in u te s t h e b a t t e r i e s a r e k e p t i n e r t u n t i l j u s t f o u rs e c o n ds b e f o r e C e n t au r s e p a r a t i o n a nd 20 s e c o n d s b e f o r es o l i d r o c k e t i g n i t i o n . A f t e r a c t i v a t i o n , i n which a ne l e c t r o l y t e i s i n j e c t e d i n t o t h e c e l l s , t h e b a t t e r i e sa r e a t f u l l v o l t a g e i n o ne -h al f s e c o n d a n d r e a d y f o ru s e i n t w o s e c o n d s .

Computer Command Subsysten

H e a r t of t h e on bo ar d c o n t r o l s y s t em i s t h e c o m -p u t e r command su bsy stem ( C C S ) w h i c h p r o v i d e s a s e m i -a u t om a ti c c a p a b i l i t y t o t h e s p a c e c r a f t .The C C S i n c l u d e s t w o i n d e p e n d e n t p l a t e d w i r em e m o r i e s, e a c h w i th a c a p a c i t y of 4 , 0 9 6 d a t a w o r d s .Half of ea ch memory s t o re s r e u s a b l e f i x e d r o u t i n e swhich w i l l n o t c h an g e d u r i n g t h e m i s s i o n . The s ec on dh a l f i s r e p r og r a m m a b le b y u p d a t e s f r o m t h e g r o u n d .M ost commands t o o t h e r s p a c e c r a f t s u b s y st e m s a r eis su e d f rom t h e CCS memory, which, a t a n y g i v e n t i m e ,i s l oa de d w i t h t h e s eq ue n ce s a p p r o p r i a t e t o t h e m i s s io nphase . The C C S a l s o ca n deco de commands from t h eg ro un d an d p a s s them a l o n g t o o t h e r s p a c e c r a f t s u b-s y s t e m s .U nder c o n t r o l o f a n a c c u r a t e o n bo ar d c l o c k , t h eCCS co un ts hou rs , min u tes o r s ec on ds u n t i l s o m e p r e -program med i n t e r v a l h a s e l a p s e d a nd t h e n b r a n c h e si n t o s u b r o u t i n e s s t o r e d i n t h e memory wh ic h r e s u l ti n commands t o o t h e r s u b s y st e m s .ca n be a s i n g l e command o r a r o u t i n e w hic h i n c l u d e smany commands ( e . g . m a n ip u l a t i n g t h e t a p e r e c o r d e rd u r i n g a p l a y b ac k s e q u e n c e ) .

A s e q u e n c i n g e v e n t

The CCS ca n i s s u e commands s i n g l y f r o m o n e o f i t st w o p r o c e s s o r s o r i n a p a r a l l e l o r tandem s t a t e f romb o th p r o c e s s o r s . An e x am p le o f CCS d u a l c o n t r o l i st h e e x e c ut i o n of t r a j e c t o r y c o r r e c t i o n ma ne uv er s.

TCM t h r u s t e r s a r e s t a r t e d w i t h a tandem command( b o t h p r o c e s s o r s must s e n d c o n s i s t e n t c ommands t o as i n g l e o u tp u t u n i t ) and s t op p ed w i th a p a r a l l e l c o m -mand ( e i t h e r p ro c e s so r w o rk in g t hr o ug h d i f f e r e n to u t p u t u n i t s w i l l s t o p t h e b u r n ) .- more -


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The C C S can survive any single internal fault.Each funtional unit has a duplicate elsewhere in thesubsystem.

Attitude Control and PropulsionStabilization and orientation of the spacecraftfrom launch vehicle separation until end of the missionis provided by two major engineering subsystems --attitude and articulation control (AACS) and propulsion.

Propulsion SubsystemThe propulsion subsystem consists of a large solid-

propellant rocket motor for final Jupiter transfertrajectory velocity and a hydrazine blowdown systemwhich fuels 16 thrusters on the mission module andeight reaction engines on the propulsion module.The single hydrazine (N3Hd) supply is contained

within a 0.71-rn (28-in.) diameter spherical titaniumtank separated from the helium pressurization gas by aTeflon filled rubber bladder. The tank, located inthe central cavity of the mission module's 10-sidedbasic structure, will contain 105 kg (231 lb.) of hy-drazine at lauqch and will be pressurized at 2 , 9 0 0 , 0 0 0newtons/meters (420 p s i ) . . As the propellant isconsumed, the helium pressure will decrease to a mini-mum of about 9OO,OC?O newtons/meters2 (130 psi).

All 24 hydrazine thrusters use a catalyst whichspontaneously initiates and sustains rapid decompo-sition of the hydrazine.

0.89 N (0.2-lb.) thrust. Four are used to executetrajectory correction maneuvers; the others in two re-dundant six-thruster branches, to stabilize thespacecraft on its three axes.titude control thrusters is needed at any time.

The 16 thrusters on the mission module each deliver

Only one branch of at-

Mounted on outriggers from the propulsion moduleare four 445 N - ( l O O - l b . ) thrust engineswhich, during solid-motor burn, yrovide thrust-vectorcontrol on the pitch and yaw axes. Four 22.2-N (5-lb-)thrust engines provide roll control.

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The s o l i d r o c k e t , w hi ch w e ig hs 1 , 2 2 0 k g ( 2 , 6 9 0 l b . )i n c l u d i n g 1 , 0 6 0 kg ( 2, 34 0 l b . ) o f p r o p e l l a n t , d e ve lo p sa n a v e r a g e 6 8 , 0 0 0 newton ( 1 5 , 3 0 0 l b . ) t h r u s t d u r in g i t s4 3- se co nd b u r n d u r a t i o n .A t t i t u d e and A r t i c u l a t i o n C o n t r o l S ub sy st em

The AACS i nc lu de s an onboard compute r c a l l e dH Y PA CE ( h y b ri d program mab le a t t i t u d e c o n t r o l e l e c t r o -n i c s ) , re d u n d a n t Sun s e n s o r s , r e d u n d a n t C an op us z t a rt r a c k e r s , t h r e e t wo -a xi s g y r o s an d s c a n a c t u a t o r s f o rp o s i t i o n i n g t h e s c i e n c e pl a t f o r m .The The H Y PA CE c o n t a i n s two re d u n d an t 4 , 0 9 6 ~ w o r dp l a t e dw i r e m e m o r i e s -- p a r t o f w hic h a r e f i x e d and p a r t re -

programmable -- r e d u nd a n t p r o c e s s o r s and i n p u t - o u t p u td r i v e r c i r c u i t s . F o r a n o mi na l m i s s i o n , t h e m e m o r i e sw i l l b e c h a n g e d o n ly t o m o d if y p r e d et e r m in e d c o n t r o li n s t r u c t i o n s .I n j e c t i o n P r o p u l s io n C o n t r ol

B ec au se o f t h e e n er g y r e q u i r e d t o a c h i e v e a J u -p i t e r b a l l i s t i c t r a j e c t o r y w it h an 8 0 0 kg ( 1 7 5 0 l b . )p a yl o ad , t h e s p a c e c r a f t l a u n ch e d by t h e T i t a n I11 E/C e n t a u r i n c l u d e s a f i n a l p r o p u l s iv e s t a g e which a d d sa v e l o c i t y i n c re m e nt o f a b o u t 7 , 2 0 0 kmps ( 4 , 5 0 0 m p h ) .

T h e s o l i d r o c k e t m o to r i n t h e p r o p u l s i o n m o du le i si g n i t e d 1 5 s ec on ds a f t e r t h e s p a c e c r a f t s e p a r a t e s f romt h e C e n ta u r and b u r n s f o r a b o u t 4 3 s e co n d s. F i r i n gc i r c u i t s t o t h e m oto r a r e arm ed d u r i n g t h e l a u n c h v e-h i c l e c o u n t d o w n .The four 100-lb. t h r u s t e n g i n e s p r o v i d e p i-t chand yaw a t t i t u d e c o n t r o l a nd t h e f o u r 5-lb.t h r u s t e n g i n e s p r o v id e r o l l c o n t r o l u n t i l b u rn ou t o ft h e s o l i d r o c k e t m o t or . The h y d r a z i n e e n g i n e s r e s p on dt o p u l s e s f r om t h e AACS's c o m p u te r . O n ly two p i t c h -

yaw and two r o l l e n g i n e s a t m o s t a r e t h r u s t i n g a t anyg i v e n t i m e .

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P r i o r to solid rocket ignition and following burn-out, only the smaller roll engines are required untilthe propulsion module is separated from the missionmodule. They are so oriented on the propulsion modulethat, by proper engine selection by the AACS, attitudecontrol is maintained on all three axes.Approximately 11 minutes after solid rocket burnout,the propulsion module is jettisoned. Several secondsearlier, the propellant line carrying hydrazine fromthe missionmodule to the propulsion module is sealedand separated.

Celestial Reference ControlThe Sun sensors, which look through a slot in thehigh gain antenna diah, are electro-optical devicesthat send attitude position error signals to HYPACE,which, in turn, signals the appropriate attitude con-trol thruster to fire and turn the spacecraft in theproper direction. Sun lock stabilizes the spacecrafton two axes (pitch and yaw).The star Canopus, one of the brightest in thegalaxy, is the second celestial reference for three-axis stabilization. Two Canopus trackers are mountedso that their lines of sight are parallel. Only oneis in use at any one time. The star tracker, throughHYPACE logic, causes the thrusters to roll the space-

craft about the already fixed Earth or Sun pointed rollaxis until the tracker is locked on Canopus. Bright-ness of the tracker's target star is telemetered tothe ground to verify the correct star has beenacquired.To enhance downlink communications capability, theSun sensor will be electrically biased (offset) by com-mands from the computer command subsystem to point theroll axis at or as near the Earth as possible. The Sunsensor can be biased plus and minus 20 degrees in both

pitch and yaw axes.

is the normal attitude control mode for crmise phasesbatween planets.Three axis stabilization with celestial reference

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I n e r t i a l R e f e r e n c e C o n t r o lThe s p a c e c r a f t ca n b e s t a b i l i z e d o n o ne ax i s ( r o l l )o r a l l t h r e e a x e s w i t h t h e AACS's i n e r t i a l r e f e r e n ce

u n i t , c o n s i s t i n g o f t h r e e gy ro s .A p pr o pr ia t e i n e r t i a l r e f e r en c e modes a r e usedw he nev er t h e s p a c e c r a f t i s n o t on Su n- st ar c e l e s t i a ll o c k . Such s i t u a t i o n s i n c l u d e : m a in t ai n i ng i n e r t i a lr e f e re n c e f rom C en ta ur s e p a r a t i o n u n t i l i n i t i a l ce l e s -t i a l a c q u i s i t i o n i s achieved: p u r p o s e l y t u r n i n g t h e

s p a c e c r a f t o f f S u n - st a r l o c k t o do d i r e c t e d t r a j e c t o r yc o r r e c t i o n s o r s c i e n c e i n s t r u m e n t m ap pi ng s o r c a l i b r a -t i o n s : p r o v id i n g a r e f e r e n c e w h e n t h e Sun i s o c c u l t e d ;an d p r o v i d i n g a r e f e r e n c e when co n c e rn e x i s t s t h a tt h e C anopus o r Sun sen so r w i l l d e t e c t s t r a y i n t e n -s i t y f r o m u n w a n t e d s o u r c e s -- p l a n e t s , r i n g s , s a t e l l i t e s .Each g y r o h a s a s s o c i a t e d e l e c t r o n i c s t o p r o v i d ep o s i t i o n i n fo r m at i on a b o u t t w o o r t h o g o n a l a x e s ( G y r o A :p i t c h and yaw, G yro B: r o l l and p i t c h , Gyro C : yawa nd r o l l ) . N o rm a ll y, two g y r o s w i l l be on f o r a n y i n -e r t i a l m ode. The gyros have two s e l e c t a b l e r a t e s , o n e

t h e o t h e r f o r m i s s i o n m odule c r u i s e and t r a j e c t o r yc o r r e c t i o n a nd s c i e n c e ma ne uv er s.-- h i g h r a t e -- f o r p r o p u l s i o n module i n j e c t i o n phase:

T r a j e c t o r y C o r r e c t i o n M an eu ve rsT h e Voyager t r a j e c t o r i e s a r e p lanned a round e i g h tt r a j e c t o r y c o r r e c t i o n m aneuvers ( T C M ) w i t h e a c h s p a c e -c r a f t b e tw e en l a u n c h a nd S a t u r n e n c o u n t e r . M i s s i o n re -q u i re m e n ts c a l l f o r e x t r em e l y a c c u r a t e m an eu ve rs t oreach t h e d e s i r e d z o n e s a t J u p i t e r , S a t u r n and t h et a r g e t s a t e l l i t e s . T o t a l v e l o c i t y in cr em en t c a p a b i l i t yf o r each s p a c e c r a f t i s a b o u t 724 h / h r ( 4 5 0 m p h ) .The f i r s t m aneu ver i s p la nn ed f o r t h e p e r i o d fro ml a u n c h p l u s f i v e d a ys t o l au n ch p l u s 1 5 days . Theburn may t a k e s e v e ra l h o u r s , d e p e n d i n g u po n l a u n c h ve-h i c l e and i n j e c t i o n p ha s e t r a j e c t o r y e r rors and maybe d o ne i n s e v e r a l p a r t s b e c a u s e of t h e r m a l c o n s t r a i n t sa t t h i s s u n - s p a c e c r a f t d i s t a n c e . Subsequen t T C M s w i l ln o t b e so c o n s t r a i n e d . T h r e e m or e m a n e u ve r s will b ee x ec u te d p r i o r t o c l o s e s t approach t o J u p i t e r a nd f o u rm ore b et w ee n J u p i t e r a nd S a t u r n .

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TCM sequencing is underecontrol of the computercommand subsystem (CCS) which sends the required turnangles to the AACS for positioning the spacecraft atthe correct orientation in space and, at the propertime, sends commands to the AACS to start and stopthe TCM burn. Attitude control is maintained by pulse-off sequencing of the TCM engines and pulse-on sequen-cing of two attitude control roll thrusters. Positionand rate signals are obtained from the gyros. Followingthe burn, reacquisition of the cruise celestial re-ferences is accomplished by unwinding the commandedturns -- repeating the turn sequence in reverse order.A l l TCMs are enabled by ground command.

Science Platform (Articulation Control)

Voyager's two television cameras, ultravioletspectrometer, photopolarimeter and infrared spectro-meter and radiometer are mounted on a scan platformwhich can be rotated about two axes for precise point-ing at Jupiter, Saturn and their satellites during theplanetary phases of the flight. The platform is lo-cated at the end of the science boom. Total gimballedweight is 107 kg (236 lb.)Controlled by the attitude and articulation con-trol subsystem (AACS), the platform allows multiplepointing directions of the instruments. Driver circuitsfor the scan actuators -- one for each axis -- are lo-

cated in the AACS computer. The platform's two axesof rotation are described as the azimuth angle motionabout an axis displaced 7 degrees from the spacecraftroll axis (perpendicular to the boom centerline)and elevation angle motion about an axis perpendi-cular to the azimuth axis and rotating with the azimuthaxis. Anglar range is 360 degrees in azimuth and 210degrees in elevation.The platform is slewed one axis at a time withselectable slew rates in response to computer commandsubsystem commands to the AACS. Slew rates are: highrater 1 degree per second; medium rate: . 3 3 degree

/s ; low rate; .083 degrees/s; and a special UVS lowrate: .0052 degree/s Camera line of sight will becontrolled to within 2 . 5 milliradians.

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T e m p e r a t u r e C o n t r o l

The two V oyager s p a c e c r a f t a re d e s i g n e d t o o p e r a t ef a r t h e r f r om E a r t h t h a n a n y p r e v i o u s man made o b j e c t .S u r v i v a l d e pe n ds g r e a t l y u pon k e e p i ng t e m p e r a t u r e sw i t h i n o p e r a t i n g l i m i t s w h il e t h e s p a c e c r a f t t r a v e r s e sa n en v ir on m en ta l r an g e of o ne s o l a r c o n s t a n t a t t h eE a r t h d i s t a n c e t o f o u r p e r c e n t of t h a t s o l a r i n t en -s i t y a t J u p i t e r and l e s s t h a n o ne p e r c e n t a t S a t u r n .

U n pr ot ec te d s u r f a c e s a t t h e S a t u r n r a n g e , n e a r l yo ne b i l l i o n m i l e s f ro m t h e S un c a n r e a c h 1 9 6 C( 3 2 1 F ) be low ze ro -- t h e t e m pe ra tu re o f l i q u i d n i t r o -gen .

B o th t o p a n d bo t to m o f t h e m i s s i o n m o d u l e ' s b a s i cd ec ag on s t r u c t u r e a r e e n c lo s e d w it h m u l t i - l a y e r t h er m a lb l a n k e t s t o p r ev e n t t h e r a p i d loss o f h e a t t o t h e c o l dof sx>ace . The b la nk e t s a r e sandw iches o f a lum in izedM y la r, s h e e t s o f T e d l a r f o r m i c ro m e te r oi d p r o t e c t i o na nd o u t e r b l a c k K apton c o v e r s w hich a r e e l e c t r i c a l l yc o n d u c t iv e t o p r e v e n t t h e a c c um u l at i on of e l e c t r o -s t a t i c c h a r g e s .

A ls o e x t e n s i v e l y b l a n k et e d a r e t h e i n s t r u m e n t s ont h e s c a n p l a t f o r m . S m a l l e r b l a n k e t s a nd t h e r m a l w ra pc o v e r e i g h t e l e c t r o n i c s b a y s , boom a nd b ody -m ou nted i n -s t ru m e n ts , c a b l i n g , p r o p e l l a n t l i n e s and s t r u c t u r a ls t r u t s . Only a few e x t e r i o r e l em e n ts o f t h e s p a c e c r a f ta r e n o t c l a d i n t h e b la ck f i l m -- t h e h i g h g a i n a n te n nar e f l e c t o r , p la sm a s e n s o r s , s u n s e n s o r s and a n t e n n af e e d c o n e s .

T e mp e ra tu re c o n t r o l o f f o u r o f t h e 1 0 e l e c t r o n i c scompar tments i s p r o vi d ed by t h e r m o s t a t i c a l l y - c o n t r o l l e dl o u v e r a s s e m b l i e s w hic h p r o v i d e a n i n t e r n a l o p e r a t i n gr a n g e n e a r room t e m p e r a t u r e . The l o u v e r s a r e r o t a t e do p en by b i m e t a l l i c s p r i n g s when l a r g e a mo un ts o f h e a ta r e d i s s i p a t e d . T he se b a ys c o n t a i n t h e power c on d i -t i o n i n g eq u ip m en t, t h e r a d i o power a m p l i f i e r s , t h eH Y P A C E a nd t h e t a p e r e c o r d e r . M i n i- l ou v e rs a r e l o -c a t e d o n t h e s c a n p l a t f o r m , c os mi c r a y i n s t r u m e n t a nda nd t h e Sun s e n s o r s .

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R a di o di s ot o pe h e a t i n g u n i t s ( R H U ) , smal l non-pow er -us ing hea te r e l e m e n t s which g e n e r a t e one w a t tof t h e r ma l e n e r g y , a r e l o c a t e d o n t h e magnetometer sen -s o r s an d t h e Sun s e n s o r s . N o RHUS a r e u se d n e a r i n -s t r u m e n t s w h i c h d e t e c t c h a r g e d p a r t i c l e s .E l e c t r i c h e a t e r s a r e l o c a t e d t h ro u gh o u t t h e space -c r a f t t o p ro v i de a d d i t i o n a l h e a t d u r i n g c e r t a i n p o r t i o n sof t h e m i ss i on . Many of t h e h e a t e r s a r e t u rn ed offwhen t h e i r r e s p e c t i v e v a l v e s , i n s t r u m e n t s o r s ub as -s e m b l i e s a r e o n a n d d i s s i p a t i n g p o w e r .

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MISSION PROFILE

T r a j e c t o r i e s f o r t h e Voyager f l i g h t s were chosenn o t o nl y t o g i v e s c i e n t i s t s c l o s e up looks a t t h e p l a n e t sb u t a t many impor tant s a t e l l i t e s .a m i s s i o n t o more t h a n 1 5 m a jo r b o d i e s i n t h e s o l a rsys t em .

I n f a c t , Voyager i s

A c c or d in g t o t h e m i s s i o n p l a n , V oy aq er 2 w i l l b el a un c h ed f i r s t . V oy ag er 1 w i l l f l y a f a s t e r t r a j e c t o r yand w i l l o v e r t a k e V oy ag er 2 b e f o r e t h e y re a c h J u p i t e r .Voyager 1 w i l l a r r i v e a t J u p i t e r f o u r m onths a h ea d o fVoyager 2 and w i l l be n i n e months o u t i n f r o n t by t h et i m e i t r e a c h e s S a t u r n .E ach Voyager uses 1 0 i n s t r u m e n t s a n d t h e s p a c e -c r a f t r a d i o t o p e rf or m 11 i n v e s t i g a t i o n s . T hey w i l ls t u d y t h e two p l a n e t s , S a t u r n ' s r i n g s , a t l e a s t 11 o ft h e i r s a t e l l i t e s a nd i n t e r p l a n e t a r y s p ac e .T h e t r a j e c t o r y f o r each s p a c e c r a f t i s u n i q u e .C o m p u t e r s i m u l a t i o n s of many p o s s i b l e f l i g h t p a t h s wereu se d f o r a n a l y s i s . The f i n a l c h oi c e w i l l a f f o r dmaximum c o v er a ge of b o t h p l a n e t s and t h e i r m a jo rs a t e l l i t e s . T h e s p a c e c r a f t w i l l make e q u a t o r i a l p a s s e sa t J u p i t e r a nd u se t h e g i a n t p l a n e t ' s g r a v i t y t o b o o s tthem towar d Sa tu rn . The Voyagers w i l l g e t good viewso f S a t u r n ' s p o l a r r e g i o n , a c l o s e f l y - by of T i t a n a n dw i l l s t u d y s e v e r a l o f i t s o t h e r s a t e l l i t e s a t c l o s er a ng e . An o p t i o n e x i s t s f o r t h e l a t e r a r r i v i n g V oy ag er --i f e v e r y t h i n g h a s g one w e l l an d t h e s p a c e c r a f t i s s t i l lh e a l t h y -- to f l y o n t o U ranu s.S c i e n t i f i c o p e r a t i o n s b e g in soon a f t e r l a u n c h , wheno b s e r v a t i o n s o f t h e E a r t h a nd Moon w i l l b e made. F i e l d sa nd p a r t i c l e s m ea su re me nt s w i l l a l s o commence s h o r t l ya f t e r l au nc h.I n a d d i t i o n t o m o n i t or i n g t h e s o l a r wind a nd r e l a t e dphenomena c o n s t a n t l y , e a c h s p a c e c r a f t w i l l , a b o u t e v e r y50 m i l l i o n m i l e s , s p i n s l ow ly t o c a l i b r a t e i n s t ru m e nt sa nd t a k e o p t i c a l me as ur em en ts i n a l l d i r e c t i o n s .

- m o r e -


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The f i r s t Voyager w i l l a p p r o a c h w i t h i n 80 m i l l i o nk m ( 5 0 m i l l i o n m i . ) of J u p i t e r on D e c . 1 5 ,1 9 7 8 . A t t h a t d i s t a n c e , J u p i t e r ' s d i s c w i l l b e l a r g eenough s o t h e n ar ro w- an gl e t e l e v i s i o n camera can b e g i ni t s " o b s e r v a t o r y p h a s e " 80 d a ys b e f o r e c l o s e s t a p pr oa ch .The camera w i l l t a k e h un d r ed s o f c o l o r i m ag es o ft h e p l a n e t . They w i l l b e r e c o r d e d o n t h e s p a c e -c r a f t ' s t a p e r ec o r d e r and t r a n s m i t t e d t o E a r t h d a i l y .U l t r a v i o l e t , i n f r a r e d an d p o l a r im e t r y o b s e r v a t i o n s o ft h e v i s i b l e d i s c of J u p i t e r a r e p l a n n e d . M a g n e t i c -f i e l d , p l as ma -d av e a n d r a d i o a st ro n om y e x p e r i m e n t s w i l lmake c o n t i n u o u s o b s e r v a t i o n s of J u p i t e r an d s p a c ea r o u n d it . C h a r g e d - p a r t i c l e s e n s o r s -- f r o m t h e p l a s m ad e t e c t o r a t t h e l ow e n d of t h e e n er g y s pe ct ru m t o t h ec o s m i c - r a y c o u n t e r a t t h e h i g h - e n e rg y e n d -- w i l lo b s e r v e s o l a r phenom ena as t h e y s e a r c h f o r t h e bo un da ry

o f J u p i t e r ' s m a gn et os ph er e.On Feb. 5 , 1 9 7 9 , when Voyager 1 i s 30 d a y s a n d 3 0m i l l i o n km ( 1 8 . 6 m i l l i o n m i . ) from J u p i t e r , t h e p l a n e tw i l l have grown t o 2 1 / 2 t i m e s t h e s i z e i t a p p ea r ed i nDecember. S c a n n i n g i n s t r u m e n t s w i l l produce morep i c t u r e s , s p e c t r a a nd o t h e r m ea su re me nts . S c i e n t i s t sc o nc e rn e d w i t h J u p i t e r ' s a tm o sp he re w i l l s e l e c t f e a t u r e so f s p e c i a l i n t e r e s t -- s u c h as t h e G r e a t Red S po t andt r a n s i e n t s to r ms . Those i n t e r e s t e d i n J u p i t e r ' ss a t e l l i t e s w i l l p r e p a r e f o r l o .n g -r a ng e a nd c l o s e - u ps t u d i e s . S c i e n t i s t s who s t u d y t h e m a gn e to sp h er e,p la sm a i n t e r a c t i o n a nd ch a rg e d p a r t i c l e s a r ou nd J u p i t e r

w i l l w a t ch f o r Vo ya ge r t o c r o s s t h e b ou n da ry b e tw e eni n t e r p l a n e t a r y s p a ce a nd J u p i t e r ' s d om ain , e x pe c t e da b o u t 1 0 d a ys b e f o r e c l o s e s t a p p ro a ch .E i g ht e en d ay s b e f o r e c l o s e s t a p pr oa c h, J u p i t e rw i l l loom t o o l a r g e f o r t h e n a rr o w- an g le camera t oc o ve r i n t h e a v a i l a b l e t i m e . i t w i l l s u r r e n d e r s u r v eyd u t i e s t o t h e w id e -a n gl e i n s t r u m e n t . The n a rr ow - an g lecamera w i l l f o l l o w s e l e c t e d f e a t u r e s . S p e ct r om e t er sw i l l s c a n t h e a tm o sp he re a n d c l o u d t o p s t o h e l pd e te rm in e t h e c o mp o si t i on and n a t u r e o f t h e b r i l l i a n tbands .

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VOYAGER FLIGHT PATHSU R A N U S


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N e a r e n c o u n t e r w i l l o c c ur d u r in g t h e f i r s t d a ysof March 1 9 7 9 ( p a g e 4 4 ) . A c t i v i t y w i l l r e a c h a peako n- bo ar d t h e s p a c e c r a f t an d a t t h e M i ss io n C o n t r o lC e n t e r a t J e t P r o p u l s i o n L a b o ra t or y . S h o r t l y b e f o r ec l o s e s t a pp ro ac h t o J u p i t e r - - a t 4 a . m . ( P S T ) ,March 5 , 1 9 7 9 - - M a r i n e r w i l l f l y w i th i n 4 1 5 , 0 0 0 km(258 , 000 m i . ) o f A m al th ea , i n n e r m o s t o f J u p i t e r ' smany s a t e l l i t e s , g iv in g s c i e n t i s t s t h e i r f i r s t c l o s el o o k a t t h e t i n y o b j e c t .

T h e s p a c e c r a f t w i l l f l a s h p a s t J u p i t e r a bo ut278 ,000 km (1 73 ,0 00 m i . ) fro m t h e s u r f a c e of t h e p l a n e t .T h e n , f o r a l m o s t tw o h o u r s , c o n t r o l l e r s w i l l l o s ec o n t a c t w i t h V oy ag er 1 as i t i s o c c u l t e d by J u p i t e rw h i l e i t s o n-b oard c om pu ter d i r e c t s t h e f l i g h t , t h ed a t a c o l l e c t i o n by i t s i n s t r u m e n t s a nd r e c o r d i n g f o rl a t e r p la y ba c k t o E a r t h . F o ll ow i ng t h i s c l o s e s ta p p r o a c h t o J u p i t e r and j u s t b e f o re t h e s p a c e c r a f te n t e r s J u p i t e r ' s shadow, t h e s p a c e c r a f t w i l l examineI o f rom 2 2 , 0 0 0 km (1 3 ,7 0 0 m i . ) . A s t h e s p a c e c r a f tp a s s e s I o it w i l l f l y t hr ou gh t h e " f l u x - t u b e , " ar e g i o n o f m a g n e t ic and p la sm a i n t e r a c t i o n b etw ee n J u p i t e rand I o . D is a pp e ar an c e o f t h e s p a c e c r a f t be h i nd J u p i t e rw i l l a l lo w s c i e n t i s t s t o s t u d y t h e u p pe r a tm os ph ere o ft h e p l a n e t as s u n l i g h t an d t h e d u a l - f r e q u e n c y (S -b an da nd X-band) r a d i o l i n k s c u t o f f a nd t h e n r e a p p e a r .A f t e r p a s s i n g J u p i t e r , V oyager 1 w i l l examinet h r e e more of t h e f o u r b i g G a l i l ea n s a t e l l i t e s :Eu rop a from 733,000 km ( 45 5,0 00 m i . ) ; Ganymede from115 , 000 k m (71 ,500 m i . ) ; and C a l l i s t o f ro m 1 2 4 , 0 0 0 km( 7 7 , 0 0 0 m i . ) .J u p i t e r ' s g r a v i t y w i l l s l i n g s h o t V oy ag er t o w a rdS a t u r n , 750 m i l l i o n km ( 4 6 6 m i l l i o n m i . ) f a r t h e r fromt h e Sun . V oyager w i l l c o nt in u e t o s t u d y J u p i t e r andi t s s a t e l l i t e s u n t i l e a r l y A p r i l , a bo ut a month a f t e rc l o s e s t a pp ro ac h.P l a n e t a r y o p e r a t i o n s w i t h t h e s ec on d s p a c e c r a f tw i l l b e g i n a b o u t A p r i l 2 0 , 1 9 7 9 . I t s o b s e r v a t o r yp h a s e w i l l c o n t i n u e e a r l i e r m e a s u r e m e n t s f o r a l o o ka t t h e p l a n e t t h a t c o v e r s more t h a n e i g h t mo nth s.

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TYPICAL VOYAGER FLYBYS OF JUPITER AND SATURNL A U N C H D A T E = 9 / 1 / 7 7J U P I T E R A R R I V A L D A T E = 3 / 5 / 7 9

1466,000 MI

L A U N C H D A T E = 9 / 1 / 7 7S A T U RN A R R I V A L D A T E = 1 1 / 1 3 / 8 0/ / I - -62,100 MI

L A U N C H D A TE = 8 / 2 0 / 7 7S A T U RN A R R I V A L D A TE = 8 / 2 7 / 8 1A U N C H D A T E = 8 / 2 0 / 7 7AR R IV A L DA T E = 7 / 9 / 7 9


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- 4 5 -

T o a v oi d r a d i a t i o n h az a rd s c l o s e t o J u p i t e r , t h esecond V oyager w i l l f l y a bo u t 9 J u p i t e r r a d i i ( 6 4 3 , 0 0 0km o r 400,r)OO m i . ) from t h e v i s i b l e c l ou d s u r f a c e . I tw i l l n o t r e p e a t t h e c l o s e f l y b y o f I o . I t w i l l s u r v e yC a l l i s t o from 2 2 0 , 0 0 0 k m ( 1 3 7 , 0 0 0 m i . ) and Ganymedefrom 55 , 0 00 km ( 3 4 , 0 0 0 m i . ) . I t w i l l f l y w i th i n2 0 1 , 0 0 0 km (1 25 ,0 00 m i . ) of Europa and w i l l t a k e aq u i c k look a t A ma lth ea . C l o s e s t a p pr oa c h t o J u p i t e rw i l l t a k e p l a c e J u l y 1 0 , 1 9 7 9 . The rem ainder of t h emonth a n d t h e f i r s t week i n A ug us t w i l l b e t a k e n upw i t h o ut bo un d o b s e r v a t i o n s .

About a y e a r a f t e r t h e J u p i t e r p h as e of t h e m is s i onends , V oyager 1 w i l l b e g i n i t s s t u d i e s of S a t u r n --Aug. 2 4 , 1 9 8 0 .The im ag e o f t h e r i n g e d p l a n e t w i l l grow i n t h ena r row -ang le camera 's f i e l d o f view th ro ug h t h e f a l lof 1980. By l a t e Q c t o b e r , t h e r i n g s w i l l be t o o b i g t ob e c a p t u re d i n a s i n g l e f rame and it w i l l b e n e c e s s a r yt o mosaic m u l t i p l e f r a m e s . N o one knows how e x t e n s i v eS a t u r n ' s m a g n e t o s p h e r e i s , s o t h e p a r t i c l e s a nd f i e l d si n s t r u m e n t s w i l l b e g i n co n t in u o us h i g h - r a t e d a t aa c q u i s i t i o n a m o n t h b e f o r e t h e N o v . 1 2 c l o s e s ta p p r o a c h .P l a n s f o r t h e f i r s t Voyager c a l l f o r a f l y b yw i t h i n 4 , 0 0 0 km (2 , 5 0 0 m i . ) o f t h e s o u t h e r n r e g i o n so f t h e ma jo r s a t e l l i t e T i t a n , w ho se d i a m e t e r i s a b o u t5, 80 0 km ( 3 , 6 0 0 m i . ) and whose m a s s i s a b o u t d o u b l et h a t o f E a r t h ' s moon. The s p a c e c r a f t w i l l f l y p a s tT e t h y s a b o u t an h o u r a nd a h a l f b e f o r e i t r e a c h e sS a t u r n a nd t h e n w i l l b e o c c u l t e d b o t h fr om E a r t h a n dt h e S u n .Voyager 1 w i l l f l y p a s t S a t u r n ' s s o u t h e rn hemi-sp he re , ab ou t 138,000 km (85,800 m i . ) from t h e c e n t e ro f t h e p l a n e t . W id e- an gl e a n d n a r r o w - an g l e c a m e r a s a n dp h o to m e tr i c , u l t r a v i o l e t an d i n f r a r e d i n s t r u m e n ts w i l ls t u d y S a t u r n a nd i t s r i n g s i n t e n s i v e l y . The m ag neto-s p h e r e a n d ac co mp an yi ng r e g i o n s o f t r a p p e d c h a r g e

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