Please do NOT post ITAR-restricted content on this site.


T he Ma g ne t o sph e r i c M u l ti sca l e ( MM S ) m i ss i on i s a N a ti o n al A e r ona u t i cs and Space A d m i n i s t r a ti o n ( NA S A ) S c i en c e M i s s i on D ir e c t o r a t e ( SM D ) H e l i op hy s i cs D i v i s i on f li g ht p r o j e c t i n t he So l ar Te r r e s t r i a l P r obes ( S T P ) P r o g r a m . MMS i s a spa c e ph y s i cs r e s ea r c h m i ss i on t o d i sco v er t he f u n da m en t al p l as m a ph y s i cs p r o c es s es of m a g n e t i c r ec o nne c t i on i n t he E a rt h s m a g ne t osp h e r e . M a g ne t i c r ec o nne c t i on o cc u r s w hen t he ch a r g ed pa r t i c l es and w a v e ene r gy e m ana t i ng fr om t he sun i n t he So l ar W i n d i n t e r a ct wi t h t h e Ea rt h s m a g ne ti c f i e l d. F ou r i d e n t i c a ll y i n s t r u m en t ed s a t e l l i t es wi l l m easu r e e l e c t r i c and m a g ne ti c f i e l d s, f a s t p l as m a, en e r g e t i c p a r ti c l e s , and hot p l as m a co m pos i t i on at t i m e sca l es o f m il l i se c onds t o se c onds and spa t i a l s c a l es o f t ens t o hu nd r e d s of k m . T he sa t e l l i t e s w i l l f l y i n a t e t r ahe d r on f o r m a ti on t o e x p l o r e t he da y s i de o f t he m a g ne t opa u se a n d t he n i g ht s i de of t h e m a g ne t o t a i l i n t h r ee d i m e n s i o n s. T he f o ur sa t e l l i t e s w il l be l au n ched t o g e t h e r i n a s t ac k ed co n fi g u r a t i on i n t o an e l l i p t i c al E a r t h o r b i t w it h an apo g ee of 12 R e.

 

T he sp e c i f i c M MS s c i e n ce o b j e c t i v es a r e:

 

              D e t e r m i ne t he r o l e p l a y ed by e l ec t r on i n e r ti a l e ff ec t s and t u r b u l e n t d i s s i pa ti on i n d r i v i ng m a g ne ti c r ec o nne c t io n i n t h e e l ec t r on d i f f u s i on r e g i on.

              D e t e r m i ne t he r a t e o f m a g n e t i c r econ n ec t i on and t he p a r a m e t e r s t hat co n tr o l i t .

              D e t e r m i ne t he r o l e p l a y ed b y i on i n e r t i a l e f f e c t s i n t he ph y s i cs o f m a g ne ti c r econ n ec t i on.

 

2.2. M i s s i on C o n ce p t

T he M MS m i ss i on e m p l oy s f our i de n t i c a ll y i n s t r u m en t ed s p i n n i ng spa c ec r a f t o r b i t i ng t he E a r t h i n a t e t r a h ed r al co n fi g u r a t i on t o conduct d e f i n i ti v e i n v es ti g a ti ons of m a g ne ti c r e co n nec t i on i n k ey bounda r y r e g i ons of t h e E a r t h s m agne t o s ph e r e. T he p r oc e ss of m a g ne ti c r eco n ne c ti o n, w h i ch co n tr o l s t he fl ow o f ene r gy , m ass, and m o m en t um w it h i n a n d a c r o s s p l a s m a bounda r i es, o cc u r s t h r o u g hout t h e u n i v e r se a nd i s f unda m en t a l t o o u r un d e r s t an d i ng of a s t r oph y s i c al a nd so l ar s y s t em p l as m as.   I t i s on l y i n t he E a r t h s m a g ne t osph e r e, ho w e v e r , t hat i t i s r ea d i l y acc e s s i b l e f or s us t a i n ed s t u dy t h r o u g h t he i n s i t u m easu r e m e n t of p l as m a p r op e r t i e s and of t he e l e c t ri c and m a g ne ti c f i e l ds t h a t g o v e r n t h e be h a v i or of t he p l as m as.

 

T h r ou g h h i g h - r eso l u ti on m eas u r e m en t s m ade by e a ch spa c e c r a f t , w h o se sep a r a t i ons c an b e v a r i ed fr om t ens o f km t o a f ew hund re ds of k il o m e t e r s, M MS w i l l p r o b e t he c r u c i a l m i c r os c op i c ph y s i cs i n v o l v ed i n t he s e f unda m en t a l p r o ce ss es; d e t e r m i ne t he 3 - D g e o m e tr y of t he p l as m a, fi e l d , and cu r r ent s tr u c t u r es asso c i a t ed w it h t he m ; and r e l a t e t h e i r m i c r o - sca l e d i m ens i on t o p h eno m ena oc c u r r i ng on t he m esos c a l e. B y acqu iri ng da t a s i m u lt a n eous l y at m u lti p l e p o i n t s i n space, M MS w i l l be a b l e t o d if f e r en t i a t e b e t w e e n spa t i a l v a ri a ti o n s and t e m po r al e v o l u t i on, t hus r e m o v i ng t he space - ti m e a m b i g u it y t hat has li m it ed s i n g l e - spac e c r a f t s t ud i es o f m a g n e t osp h e r i c p l as m a p r o ce s ses.

 

A t w o - phase l o w - i nc li n a ti on o r b i t s t r a t e g y w il l p r o be t he m ost li k e l y r econ n ec t i on s i t e s on bo t h t h e da y s i de m a g ne t opau s e ( P h ase 1 ) and i n t h e m a g ne t o t a i l ( Ph a se 2 ) . Ph a se 1 w i l l con s i st of an e l l i p t i ca l


 

Ea rt h o r b i t wi t h an apo g ee of 12 R E + / - 1 R E Phase 2 w i l l con s i s t o f a n e l l i p t i cal Ea r t h o r b i t w i t h a n apo g ee of 2 5 R E + / - 5 R E ( F i g u r e 2 - 1 ) .

 

F i gu r e 2 - 1: Lo c a t i o n o f M a gn e t ic R e c onn ec t i o n o n th e D a y s i d e/Ni ght si d e

 

T he R e g i o n s O f ( s c i e nc e ) I n t e r est ( RO I ) a r e de f i n e d as g eocen t r i c apo g ee d i s t a nces >9 R E f or P h ase 1, and >15 R E f o r Pha s e 2. T h e r e i s no f o r m a ti o n r e qu i r e m ent or r e g i on o f s c i e n ce i n t e r e s t d e fi n ed du r i ng t h e tr a n s i t i on f r om Phase 1 t o Phase 2.


 

F i gu r e 2 - 2: D a t a C o l l ec t i o n S t r a t e g y O v e r v i ew

 

T he f o u r MMS s p ac e c r a f t w il l o p e r a t e i n t h e S l ow S u r v ey m ode app r ox i m a t e l y 50% of t he t i m e du ri ng each o r b i t . F a st S u r v ey m ode oc c u r s w it h i n t he p r i m a r y sc i ence r e g i on of i n t e r e s t . B u r st d a t a i s a l s o co l l e c t ed d u r i ng t he F a st S u r v ey pe ri od.

 

T w o t y pes of sc i en c e d a t a t y pes a r e u sed t o m eet t he m i s s i on r eq u i r e m en t s. T h e se da t a t y pes a r e :

 

              Surv e y da t a :   These d a t a a r e c o ll e c t ed co n ti n u ou s l y fr om a l l i n s tr u m en t s t h a t a r e po w e r ed and s t o r ed i n t h e m ass m e m o r y m odu l e o f t he C I D P. The o r b i t i s d i v i ded i n t o f a s t s u r v ey and s l ow su r v ey pe r i ods.    F a s t s u rv ey da t a a r e co l l e c t ed d ur i ng t he p r i m a r y sc i e nce r eg i on of i n t e r e s t ( RO I ) pe ri od of t h e o r b i t w h il e t he s l ow su r v ey da t a a r e c o l l e c t ed a t a s l o w e r r a t e d u r i ng t he r e g i on o f t h e o r b i t t h at i s of l ow s c i en c e i n t e r e s t The f a st and s l ow s u r v ey t i m es a r e s e t by g r ound co m m and.

              Burst d a t a T he i ns t r u m en t s p r o v i de a s t r eam of t h e h i g hest r e s o l u ti o n d a t a t o t he C I D P i n pa r a l l el w it h t h e f a s t s u r v ey da t a. A l l bu r st da t a c o l l ec t e d d u ri ng t h e f a s t s u r v ey pe ri od w i l l b e

s t o r ed i n t he m ass m e m o r y m odu l e of t he C I D P.               B u r s t i n f o r m a ti on i s t a gg ed w it h qu a l i t y

i n f o r m a ti on b as e d on a sp a cec r a f t w i d e t ri gg er s y s t e m .

 

Tr i g g er d a t a a r e a l so g ene r a t ed by a l l i n s t r u m en t s and a r e used by t he C I D P t o ca l cu l a t e qu a l i t y i n f o r m a ti on and by t he S c i e nce O p e r a t i ons C en t er ( S O C ) t o s u ppo r t t he s e l e c t i on of t he p r i o r it y b u r s t d a t a t o o p ti m i z e sc i e nce d a t a do w n l i n k E v e r y i ns tr u m ent s upp l i e s a s et o f t ri gg er d a t a o nce e v e r y ~10 secon d s.

 

I n t e r - space c r a f t sep a r a ti o n d i s t a n ces b e t w een t h e fo ur s p ac e c r a f t i n t he t e tr ah e d r on w i l l be chan g ed be t w e e n 160 k m and 10 k m ( Phase 1) and be t w een 4 00 km and 30 k m ( Phase 2 ) by g r ound co mm and t o l oc a t e t h e o p ti m al d i s t a n ce t o o p t i m i z e t he opp o rt u n i t i e s t o c ap t u r e r ec o nnec t i on e v en t s.    T h e obse r v a t o r i es w i l l t h en b e p l ac e d i n t h i s o p t i m al d i s t a n ce f o r t he r e m a i nder of t h a t Phase.


 

2.3. Sc i en c e I n s t r u m e n t a t i on

T he S M AR T ( So l v i ng Ma g ne t o s ph e ri c A c c e l e r a t i on, R econn e c t i on a n d Tu r b u l e nc e) I ns tr u m ent Su i t e w i l l m a k e t he r e q u i r ed h i g h - ti m e r e s o l u ti o n m easu r e m en t s of p l as m as, e l e c t r i c f i e l ds a nd m a g ne ti c f i e l d s a n d p r o v i de i m po rt a n t supp o r ti ng m easu r e m en t s of e n e r g e t ic p a r t i c l es and i o n co m pos i t i on. T h e SM A R T I S cons i s t s of t he f o ll o w i ng c o m p l e m ent of i n s tr u m en t s :

 

              T he FI ELD S i nv e s t i ga t i o n i n c l ud e s a s ens o r s u i t e cons i s t i ng of a x i a l a n d s p i n - p l ane doub l e- p r obe e l e c t ri c - fi e l d s e ns o r s ( AD P and S D P ) , t w o fl u x - g a t e m a g ne t o m e t e r s ( A F G and D F G ) , a sea r ch - co i l m a g ne t o m e t er ( S C M ) , and an e l e c t r on d ri f t i n s tr u m ent ( E D I ) . T h ese i n s tr u m en t s m easu r e D C m a g ne ti c f i e l d w i t h a r e so l u t i on o f 1 0 m s, D C e l ec t r i c fi e l d w i t h a r e so l u t i on of 1 m s, e l ec t ri c p l as m a w a v es t o 100 k H z , and m a g ne ti c p l as m a w a v es t o 6 k H z .

              T he E nerge t i c P ar t i c l e D e t e c t or ( E P D ) i n c l ud e s an Ene r g e ti c I on Spec tr o m e t er ( E I S) and an a ll - sky pa rt i c l e s a m p l er ca l l ed t he F l y s E y e Ene r g e t i c Pa r t i c l e S e ns o r ( FEEPS ) T h ese i n s tr u m en t s m eas u r e t he e n e r g y - a n g l e d i s t r i b u ti on and co m pos i t i on o f i ons ( 20 t o 500 k e V ) a t a ti m e r e so l u t i on o f < 30 s e conds, t h e e ne r g y - an g l e d i s t r i b u ti o n o f t o t al i o n s ( 45 500 k e V ) a t a ti m e r e so l u t i on o f < 10 s e conds, and t h e c o a r se a nd fi ne e n e r g y - an g l e d i s t ri b u ti on of en e r g e t i c e l e c t r ons ( 25 – 5 00 k e V ) a t ti m e r es o l u ti o n s o f < 0.5 a n d < 10 s econ d s, r es p ec t i v e l y .

              T he F a s t P l a s m a Ins t r u m ent ( FPI) i n c l u d es f o u r dual e l e c tr on s p ec t r o m e t e r s ( D E S ) a n d f o u r dual i on sp e c t r o m e t e r s ( D I S ) T he s e i n s tr u m en t s m easu r e t he v e l o c i t y - space d i s t ri b u t i on o f

e l e c t r ons f r om 10 eV t o 30 k eV and i ons fr om 10 eV t o 30 k eV w it h ti m e r es o l u ti o n of 30 m s,

and 150 m s, r e spe c ti v e l y

              T he H ot P l a s m a C o m po s i ti on A na l y z er ( H P CA ) m eas u r es t h e co m pos i t i on - r eso l v ed v e l oc i t y- space d i s t ri b u t i on of i o n s fr om 1 eV t o 40 k eV wi t h t i m e r eso l u ti on of 1 0 – 15 s e conds.

              T he A c t i ve Spa c ecr a f t Po t en t i a l C o n t r o l ( A SP O C ) g ene r a t es b ea m s of i n d i u m i ons t o li m i t pos i ti v e s p ace c r a f t p o t e n ti a l s t o + 4 V i n o r d e r t o i m p r o v e t he m eas u r e m en t s o b t a i ned by FP I , H P CA , AD P, and S D P.

T he i n s t r u m ent s u it e s a r e s uppo r t ed by t h e C e n tr a l I ns tr u m ent D a t a P r oc e ss o r ( C I D P ) , w h i ch c o ll e c t s and s t o r e s t e l e m e tr y fr om each i ns t r u m ent and s ends i t t o t he s pa c ec r a f t f o r d o w n li n k . The C I D P

p r o v i des t i m e and sp i n s y nch r o n i z a t i on a s w e l l as s w it c h ed po w e r s e r v i c e s t o t he i n s tr u m en t s, a nd f o r w a r ds co m m ands r e c e i v ed f r om t he Spa c ec r a f t A v i on i cs ( F i g u r e 2 - 3 ).


 

F i gu r e 2 - 3: M M S - S M A RT I n s t r um e n t S u i t e A r c h i t ec t u r e

 

2.4. O r b i t P h a ses a nd M i s s i on T im e li n e

MMS s f o u r s a t e l l it e s w i l l be l aun c hed t o g e t her i n a s t ac k ed co n fi g u r a t i on i n t o an e l li p t i cal E a r t h o r b i t w it h an apo g ee o f 12 R e. D u ri ng t he es t i m a t ed 4 - m on t h ch e c k out p e r i od, t he p e r i g ee w i l l be r a i s ed t o 1.2

R e v i a t h e sp a ce c r a f t p r o pu l s i on s y s t e m s. A t t he end o f t h e c h eck out p e r i od t he o r b i t a p o g ee w i l l b e ne a r t he dusk m a g ne t opause. P hase 1 wi l l co mm ence at t h i s po i n t and l a s t 1 6 m on t hs. D u r i ng Pha s e 1 t h e

MMS apo g ee wi l l s w e ep a c r o s s t he da y s i de m a g ne t opause t w i ce ( pha s e 1a and 1 b).  A t t he end of Ph a se

1b, t he apo g ee wil l be r a i s ed g r ad u a l l y t o 2 5 R e. P h ase 2 c o n t i nu e s f or an ad d i ti o n al 5.5 m on t hs. T he o r b i t w i l l be a ll o w ed t o d r i f t na t u r a ll y t h r o u g hout t h e m i ss i on l if e ti m e (i . e., i t w il l n o t be c o n t r o l l e d) .

Shou l d t he MMS m i ss i on be ex t end e d, t h e sp a ce c r a f t w i l l r e m a i n i n t he Ph a se 2 o r b i t wi t h i t s 25 R e

apo g ee ( s ee F i g u r e 2 - 4 ).


 

F i gu r e 2 - 4: M M S O r b it P h ases

 

T he t i m e li ne f o r c o l l e c ti on of s c i ence d a t a d u r i ng ea c h of t he M MS m i ss i o n p h ases i s sho w n i n F i g u r e

2 - 5.

 

 

F i gu r e 2 - 5: M M S S cie n c e Ac qu isi t i o n T i m e li n e