Voyager Backgrounder 1981

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    National Aeronautics andSpace Administration

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    i i i

    VOYAGER BACKGROUNDER .. AUGUST 1981

    For f u r t h e r i n f o r m a t i o n : RELEASE NO: 81-116

    C h a r l e s RedmondNASA Headquarters. Wa s h i n g t o n . D.C.(Phone: 202/755-3680)

    F r a n k Bris towNASA J e t P r o p u l s i o n L a b o ra t o ry . P a sa d en a . C a l i f .(Phone: 213/354-5011)

    CONTENTS

    VOYAGER SPACECRAFT ......................................... 1-26S t r u c t u r e and C o n f i g u r a t i o n ........................ 3C o m m u n i c a t i o n s ..................................... 8Power .............................................. 15A t t i t u d e C o n t r o l ................................... 20I n j e c t i o n P r o p u l s i o n C o n t r o l ....................... 2 1C e l e s t i a l R e f e r e n c e C o n t r o l ........................ 2 2T r a j e c t o r y C o r r e c t i o n Manuevers .................... 2 3S c i e n c e P l a t f o r m ................................... 24Te m p e r a t u r e C o n t r o l ................................ 25Lo w-E nergy C h a r g e d P a r t i c l e s ....................... 28M a g n e t i c F i e l d s .................................... 29

    Computer Command Subsystem ......................... 18

    VOYAGER EXPERIMENTS ........................................ 27-42Cosmic Ray ...................................... a . . 2 7 ..I n f r a r e d I n t e r f e r o m e t e r S p e c t r o m e t e r ............... 0P h o t o p o l a r i m e t e r ................................... 31P l a n e t a r y R a d i o Astronomy .......................... 3 2P l a s m a ............................................. 33P l a s m a Wave ........................................ 35R a di o S c i e n c e

    ......................................37

    T e l e v i s i o n ......................................... 38TRACKING AND DATA ACQUISITION ............................... 42MISSION CONTROL AND COMPUTING CENTER ........................ 46VOYAGER SUBCONT.CTORS ..................................... .49APPENDIX A: E a r t h - S p a c e c r a f t C o m m u n i c a t i o n s ................ 2APPENDIX B:

    U l t r a v i o l e t S p e c t ro me te r ........................... 4 1

    N a v i g a t i o n O p e r a t i o n s .......................... 58

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    THE VOYAGER S PA C E C R A F T

    Th e t w o i d e n t i c a l Voyager s p a c e c r a f t a r e d e s i g n e d t o

    o p e r a t e a t g r e a t e r d i s t a n c e s f rom E a r t h an d t h e S un t h a n r e q u i r e d

    b y a n y p r e v i o u s m i s s i o n . C om mu ni ca ti on s c a p a b i l i t y , h a r d w ar e

    r e l i a b i l i t y , n a v i g a t i o n a n d t e m p e r a t u r e c o n t r o l a r e among t h e

    major c h a l l e n g e s t h a t had t o be m e t t o o p e r a t e o v e r t h e t i m e of

    t h e m i s s i on , b e ca u se of t h e E a r t h - s p a ce c r a f t d i s t a n c e s i n vo l ve d a nd

    t h e wide r a n g e of e n v i r o n m e n t a l c o n d i t i o n s e n c o u n t e re d .

    E a c h s p a c e c r a f t a t l au nc h c o n s i s t e d of a m i s s i o n m od ul e

    -- t h e p l a n e t a r y v e h i c l e -- and a p r o p u l s i o n . m o d u l e , w h i c h p r o v i d e dt h e f i n a l e n e rg y in c r e m en t t o i n j e c t t h e m i s s i o n m od ul e o n t o t h e

    J u p i t e r t r a j e c t o r y . The p r o p u l s i o n module was j e t t i s o n e d a f t e r

    t h e r e q u i r e d v e l o c i t y was a t t a i n e d . ( F o r t h e major p a r t of t h e

    m i s s i o n , " s p a c e c r a f t " a n d " m is s io n module" w i l l be used i n t e r c h a n g e -

    a b l y . I n d e s c r i b i n g t h e p re -l au nc h c o n f i g u r a t i o n and l a u n c h p h a s e ,

    " s p a c e c r a f t " w i l l r e f e r t o t h e combined " m i s s i o n module" a n d " p r o -

    p u l s i o n m o d u l e . " )

    The l a u n c h w e i g ht o f t h e s p a c e c r a f t was 2,066 k i l o g r a m s

    (4,556 p o u n d s) , i n c l u d i n g t h e p r o p u l s i o n module w i t h i t s l a r g e ,

    s o l i d - p r o p e l l a n t r o c k e t m ot or t h a t weighed 1 , 2 0 7 k i l o g r a m s (2,660

    p o u n d s ) . A f t e r i n j e c t i o n t h e m i s s i o n m o d u le w e i g h e d 8 2 5 k i l o g r a m s

    ( 1 , 8 1 9 p o u n d s ) i n c l u d i n g a 1 1 7 k i l o g r a m s ( 2 5 8 p o u n d ) s c i e n c e

    i n s t r u m e n t p a y l o a d ' .

    L ik e t h e M a r i n e r s t h a t e x p l o r e d t h e i n n e r p l a n e t s a nd

    t h e Vi k i n g M a r s o r b i t e r s , t h e Voyager s a r e s t a b i l i z e d on t h r e e

    axes u s i n g t h e Sun an d a s t a r as c e l e s t i a l r e f e r e n c e s .

    -1-

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    Hot g a s j e t s p r o v i d e t h r u s t f o r a t t i t u d e s t a b i l i z a t i o n

    and f o r t r a j e c t o r y c o r r e c t i o n maneuver s .

    T h r e e e n g i n e e r i n g s u b sy s t e ms a r e programmable f o r o n-

    b o a r d c o n t r o l o f most s p a c e c r a f t f u n c t i o n s . The t h r e e a r e t h e

    computer command s u b s y s t e m (CCS), f l i g h t d a t a s u b s y s t e m ( F D S ) a n d

    a t t i t u d e a nd a r t i c u l a t i o n c o n t r o l su bs ys te m ( A A C S ) . Th e memories

    of t h e u n i t s can be u p d a t e d o r m o d i f i e d by ground command.

    A n u c l e a r power s o u r c e -- t h r e e r a d i o i s o t o p e t h e r m o -e l e c t r i c g e n e r a t o r s -- p r o v i d e s e l e c t r i c a l power f o r t h e space-c r a f t .

    The p o i n t a b l e s c i e n c e i n s t r u m e n t s a r e mounted on a t w o -

    a x i s s c a n p l a t f o r m a t t h e end o f t h e s c i e n c e boom. O t h e r b o d y - f i x e d

    and boom-mounted i n s t r u m e n t s a r e a l i g n e d t o p r o v i d e f o r p r o p e r

    i n t e r p r e t a t i o n o f t h e i r measu r emen t s .

    Data s t o r a g e c a p a c i t y on t h e s p a c e c r a f t i s a b o u t 5 3 6

    m i l l i o n b i t s -- a p p r o x i m a t e l y t h e e q u i v a l e n t o f 1 0 0 f u l l - r e s o l u t i o np h o t o s .

    D u a l - f r e q u e n c y c o m m u n i c a t i o n l i n k s -- S-band a nd X-band-- p r o v i d e a c c u r a t e n a v i g a t i o n d a t a an d l a r g e a mo un ts o f s c i e n c ei n f o r m a t i o n d u r i n g p l a n e t a r y e n co u n t e r p e r i o d s ( u p t o 115,200 b i t s

    p e r s e c o n d a t J u p i t e r and 4 4 , 8 0 0 b p s a t S a t u r n ) .

    -. .. r -

    T h e d o m i n a n t f e a t u r e of t h e s p a c e c r a f t i s t h e 3 . 6 6 - m e t e r

    ( 1 2 - f o o t ) d i a m e t e r h i g h -g a i n a n t e nn a t h a t , a f t e r t h e f i r s t 8 0 d a y s

    o f f l i g h t , a lmos t c o n t i n u o u s l y p o i n t s t oward E a r t h . P e r i o d i c e x c e p -

    t i o n s a r e d u r i n g t r a j e c t o r y - c o r r e c t i o n , c a l i b r a t i o n , o r s c i e n c e

    d a t a a c q u i s i t i o n a t t i t u d e m a n e u v e r s .

    W hi le t h e h i g h -g a i n a n t e n n a d i s h is w h i t e , most v i s i b l e

    -2-

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    .

    p a r t s of t h e s p a c e c r a f t a r e b l a c k -- b l a n k e t e d o r w r ap pe d f o rt h e r m a l c o n t r o l a nd mi c ro m et e or o id p r o t e c t i o n . A f e w s m a l l a r e a s

    a r e f i n i s h e d i n g o l d f o i l o r h av e p o l i s h e d a lu mi nu m s u r f a c e s .

    S t r u c t u r e and C o n f i g u r a t i o n

    The b a s i c m i s s i o n module s t r u c t u r e i s a 2 4 . 5 - k i l o g r a m

    ( 5 4- p o un d ) 1 0 - si d ed al um in um fr am ew or k w i t h 1 0 e l e c t r o n i c s p a c k a g i n g

    c o m p a r t m e n t s . T h e s t r u c t u r e i s 47 c e n t i m e t e r s ( 1 8 .5 i n c h e s ) h i g h

    a n d 1 7 8 c e n t i m e t e r s ( 7 0 i n c h e s ) a c r o s s from f l a t t o f l a t ; 1 8 8 c e n t i -

    meters ( 7 4 i n c h e s ) f r om l o n g e r o n t o o p p o s i t e l o n g e ro n . The e l e c -

    t r o n i c s a s se m b li es a r e s t r u c t u r a l e l e m e n t s o f t h e 1 0- s i de d bo x.

    The s p h e r i c a l p r o p e l l a n t t a n k t h a t c o n t a i n s f u e l f o r

    h y d r a z i n e t h r u s t e r s f o r a t t i t u d e c o n t r o l and t r a j e c t o r y c o r r e c t i o n

    m an eu v er s o c c u p i e s t h e c e n t e r c a v i t y o f t h e d ec ag on . P r o p e l l a n t

    l i n e s c a r r y h y d r a z i n e t o 1 2 s m a l l a t t i t u d e - c o n t r o l and f o u r TCM

    t h r u s t e r s o n t h e m i s s i o n module and t o l a r g e r t h r u s t - v e c t o r - c o n t r o le n g i n e s o n t h e p r o p u l s i o n m o d u l e d u r i n g l a u n c h .

    The 3 .6 6- me te r ( 1 2 - f o o t ) d i a m e t e r h i g h - g a i n p a r a b o l i c

    r e f l e c t o r i s s u p p o r t e d a b o v e t h e b a s i c s t r u c t u r e b y a t u b u l a r t r u s s

    work. T h e a n t e n n a r e f l e c t o