. Autonomous Nucleus Tracking for Con~et/Asteroid Encounters: The STARDUST Example Sllyalll l)l(askalall (818)354-3152 Sllyalll(? llov:l.j})l .ll:{sa.gov .Josc[jlI 11. Itidcl (818) 354-87’24 jcl(tr{l(l tr:lll.j[)l .ll:ts?l, g(lv Stq)ll(xl 1 ‘. Syilllot( (818)354-6933 stcl)llcll .sylll[ott (~<il)l .ll?lsa, gc)v Jet l’rol)ulsiott l,al~oratory Califorltia IIlstitu(e of ‘lkcl II Iolc)gy AIS 301- IL(I 4800 Oak Grove l)rivc l’asadclIa, Califorl~ia, 9110{1 AIIsimct S’1’ARI)US’J’ is a nlissio~t to flyl)y tlic coIIIct 4. lMA(:IN(: SYSrl’lhl Wil&2 it) early 2004 aild rcturII saln~~les of tlic COIIIEI to ~ I)artll. ])uritlg its 120-150 k[H flyby of tllc colllct llu- KAI, I’IIAN’ l~lf:l’1:1{ SII:’l’U1) cleas, a scco]ldaly science goal is to ol~taill illlagcs of 6. nlo~’rl: CA1{l,O SIAILJLAYlOAI ANI) RII;SIJI;J’S the IIUCICUS usiltg tile o]lboard tiavigatioll cal]lcra, l)UC to the 40 minute rouncl-tril) light tilllc, grouIId l)roccss- 7. ‘1’IMIN[: illg of navigation data to uIJdatc ~)oilltiag illfor]natio)l to 8. CON(:lJUSIONS ]I)ailktaitl tlic IIaclcLIs if] tlIe ca]ncra flclcl-of-view is ilm practical. ‘J’bus, a silnl)lc, rdiahlc, and fast algoritlllil was CICVCIO1)CC1 to close tile navigation loop olll)oard dur- ing ctlcouttter. ‘J’lIc algoritl]ll] uses inlages of tllc IIUCICUS 1 IN’J’I{OI)IJC’J’ION clurillg al]])roacll to ul)datc target relative shtc illforlllw tiotl. ‘J’)lis involves ccmtroiding olI tllc ilnagc to olltaill IIU- clcas cctltcr-of-fi.gurc data aIid then I)roccssiug tllc data S’1’AI{l)US’1’, tl~c fourth lnission ill NASA’s l)iscovcry tllrougll a Kaltnan filter to update tlIc sl)acccraft, I~osi- I)rogra]tl, is a Inissioll to I)c launcl}cd in early 1999, per- tion ancl attitucle. Monk Carlo sill] ulatiolw \vcrc tlICII fortn a relatively low \clocity flyby of the comet l’/Wilcl-2 Ijerformcd to test tlIc algoritl]ltl. ‘J’llesc sit[]ulatiol]s il~- ill Jailuary, 2004, and return to IIkirtll in 2006. Its ]mimary corporatcd errors ill sl)acccraft itlitial I)ositiol[ and ill at- scic]lcc goal is to collect 1000 particles of cometary clust titude kIIowlcdc to I)rcwide a ‘Irutl l’) Inodcl wllicll tlIc of greater tlla]l 15 t[licrolls durilig tile flyby and rctaru filter Itlast rccovcr froln, ‘J’IIc results of tJIP sii[Iulatiolw tllcl][ to l)artlt ill a saln~~le rcturll calwule. As secondary I)rovcd that tile algorit]lru }vas sacccssful iIl I[lailltaillillg scictlcc goals, tllc sl)acecraft will also collect. interstellar tllc lIuclcas in tllc ca~tlcra flclcl-of-vic!v assaillitlg Ilol[lillal dast ]Jar(icles a]ld ol)tai[l \\Tilcl-2 collia and nucleus iltl- valaes for tlic errol sources. II:vcn wit]l \vorst case errors, agcs during tlIc cilcountcr, l)uc to tllc size of tllc navi - tllc algoritllnl ]]crfor]ncd successfalty ill over 90[)4 of tllc gaiiol) urlccrtaitltics at tlw titoe of tl]c fil]al uplink of the cases. ctlcoarltcr scqucf Icc to tl]c spacecraft, tllc tracking of tllc IIaclc IIs duriflg tllr cllcoul]tcr usitig tllc onl)oarcl calnera catltlot l~c I)crfortilcd o~)cll-lool). 111 acldition, tile large ‘1’A 111,1:011’ CON’1’II:N’J’S (w40 IIlillatc rout, cl-trijl ligh-tilllc) }jrccludes ground in- tcrvc]ltiot] during tlIc cllcoulitcr tillic l~miod to uI)datc Ilavigatioll illfor[llatioll. ll]stcad, iiilagcs taken with tltc 1. lN’1’I{OI)lJC1’ION Calllcra start i[lg around 20 ]I]illutcs })rior to closest al]- 2. ‘1’111; hflSSION I)roacll }vill },(s used to refitle tllc coinct-relative sl)acccraft st ate, a]ld t l]crcfore tltc catncra borcsight point il]g direc- 3. F! A\~l GArl’lON tiotl to t l]e coIIIct, olll)oarcl tlkc s~lacecraft itself. ]kcause 1 of the tight turnarc)ulld IICCCM to Iilaitltaill lock, tlic oll coli)d during a])l)roach WIICII it is hiddea from view by board al&ritllm IIas to bc si]nl)lc, rcliahlc, and fasl. 1( tile \Yllipl)lc slliclcl, a periscope is lnountcd which ~wers ]Jcrforl]ls centroidillg to clcterlnillc tile ccllter of tllc co]l]ct around ttlc shield. ‘J’llis ca]ncra/Inirror/pcriscopc combi- nuc]cus, and illcorl)oraks this itlforlnatio]l into Kalt]]arl ]Iatiol] fortns tllc irtla.giag systcl]l ~vllicl~ cloublcs as both filter to update state iaformatioa. ‘1’llis pal,cr descrilm i]} tllcscicllcc al~d o]~tical ]laligatic]]li llstr~]lllcllt. detail the algorithnls used, and the rmalts of sitnula(iolls to verify tllc code. After cc,llccti]lgt lies a]lll)lcs, tl)e acrogcl isst.o}ved iatoa salnp]c rctuutl caI)sulc cqaipr)cd with at) aeroshe]l where it Ivill rclllaitl for tllc rest of tlie Inissio[l, ‘1’lic s~)acccraft tllcll rctargcts its trajectory for atl l;artl~ rcturll to oc- 2 ‘1’IJII: NJISS1ON cur 011 Jatluary 13, 2006. At 1;-1 days, tile spacecraft ])crfc)rltls its fitlal]llallclllcrt otargct tile SRCfor a land- S’l’Altl)lJSrl’ is the fourt,ll ~ilission of NASA’s l)iscovcry i[lg witllitl a 60 I)y 6.5 kIu footprint at the Air Force’s prograln, followilg hlars }’athfinder, Near lkrtll Askroid Ulall ‘J’cst aIId ‘I’rairlillg l{aIlgc (ll’J’rl’l{) facility. Several }{mdczvoas, aIld ],unar l’rospector. ‘J’l Ic ]t]issioIl is a col- IIours])ric)r toctttry, tllc SILClis jettisollecl froIiltlle It]aill lahorat iw e{fort, with J 1’1, providing the ])rojcct lnanagc- sl)acecraft ])us, }vllicll tllcll ]wrfortnsa divert mancuverto ment, I)avigat, ion, and missiolt clesig[] car)al)ilit, im, I,ock - kcclJ it fro]n also c]itcringt lie l}artl~’s atmosphere. After hecd Martin AstroI~autics ill ])cnvcr, CO I)rovidi]tg tllc lal[dillgat [J’I’’I’I{, tile aerogcl with tlIc samplesis rccov- s])acccraft and most Inissio]i olwratio]w, atId tllc U]livcr- crcd fro]n tlic SI{C and sc]lt to a facility at the Johnson sity of Wasl]ingtonj wlwrc tl}c l’ril~ci])al lilvestigator is lo- SI~acc Cclltcr for storage allcl dissclninatio]] to the sci- cated. ‘i’l Ic sl)acecraft will bc laatlclled irl ]Ili+l’’e})ruary, CIICC tealn, I’or ]Ilorc i[]forlnatio]] OH tllc S’I’AR1)US’J’ 1999 al)oard a l)elta 7436 launch vcllic]c. l)aritlg its 5 ]nissioll, scc its IIOIIIC page 011 the World Jfride JYeb at year cruise to tllc comet 1’/Jl’ild-2, it will I)crforltl OIIC lltt I)://stardust .jpl.]lasa.gov/. gravity assist using tlic I}artll to give it cnouglI etlcrgy to rcltdczvous with tlIc comet. CoIIIet flyl)y will occar olI Jarluary 1, 2004 at a colnct-relative velocity of a little over 3 NAVIGKI’1ON 6 km/s. IJuring this flyby, a unique sulmtatlcc liIIOWII as awogcl, developed at the Jet ProI)ulsioIl l,al)oratory, will be dcp]oycd to collect coma dust partic]cs. ‘1’llc vclliclc ‘1’IIc ])rilllary II~ode of]lavigation fc)r the Inission Jvill be itself Ivill t~c protechxl froln tile lly~mrvclocity iln])acts of sta]ldard ,Y-l)alid l)ol)plcr and rallgiag. Covariancc anal- tllcsc particles usiag a forward facitlg sllicld (t,erlllcd tllc ysis IIassllolvl] tliat this issafficietl( to Incet the reqaire- “\Vlli],]Jlc” sliicld, in IIonor of astro]lo]lier IIkd \Vllil)- II ICIIt S for all dccl)-sl)acc Inallcuvcrs, l;arth gravity assist, pk). ‘J’lIc I)ril]]ary science rcquirclncllt, is to c.ollcct at and I;artll return, For comet flyby IIo}vcvcr, tllc a-priori least 1000 ],articlcs of greater than 1.5 ]llicroIl size }v}licll uncertaitltics itl tlIc colnet epllclncris (arouacl 1500 ktn) irnlml tllmnsclvcs ill tllc acrogcl as tlIc sl)acecraft flies I)y froth groatlcl-l)ased observations I,rcclude usirg radio data tllc colllct. l)Llc to tile ullccrtai]lty irl tlIc Inodcls wllicll alo]ieto ]lalrig:ltet llis~)llasco ftllclllissioll, ‘J’hcrefore, the clcscribc tllc density of cfast surroulldi[lg tl~e llaclcus, tlw olllmard calncralrlust bcuscd totakcimagcso fthcco met actual flyl)y distance is still so]ncwllat ullccrtaill, alId ill- llrior to ctlcc)utltcr to improve tile co~l]ct eplwmeris k[lowl- volvcs a trade-ofl bct}vecll s])acecraft safety and Itlcctiilg cdgcsaflicicllt tol[lcct tllc 120-150 kr]lflyl)y reel LlircIllcrlt, tlw 1000 ])articlc lccluireinc]]t, With current cotna IIIOCl- Startiilg at \lJilcl-2eltcoL] lltcr (\f’)-100 days, itnagcs will CIS, tllc clistallcc is set bctwcca 120 atld 150 kIII, I)ut tllc Iw taken at tlic rate of once ])er week, ‘J’hcsc will ilk uaccrtaiaty ill tllc ]IIodcls is roughly a factor or ‘2 or 3. crease it) frcqaeIlcy to twice per }veck at W-50 days, o[lce Also duri]lg tltc flyby, coma and nuc]cas illlagcs will I)c ])er day at \\’-7 days, and OIICC pcr ]Iour at W] day. taken by tlw onhoarcl calnera tllrougll cc)lor filters atId ‘1’IIcw o])tical ]lavigation (01’NAV) images are used to downlil}kecl ill real-time to tllc groutld, cxcc~)t for a +4 su})~)ort four ‘1’rajcctory Correction Nlaneuvers (rl’Chls), Itlinutc ])criod sarrou Iidil]g Cllcouliter WIIe II tltc ittlages occurrir[g at \\’-3O days, IW1O days, \V2 clays, and M- will })c stored for later I)layback.