20 Nov 2003 K. E. Williams - CERR 1 of 7 STARDUST STARDUST Project STARDUST Project CRITICAL EVENTS READINESS REVIEW COMET P/WILD 2 ENCOUNTER NAVIGATION Kenneth E. Williams JPL: 303-411 AM / 301-427 PM LMA: MSA +1 818 354-1275 08:00 AM - 05:00 PM PST 20 Nov 2003
STARDUST Project CRITICAL EVENTS READINESS REVIEW COMET P/WILD 2 ENCOUNTER NAVIGATION Kenneth E. Williams. JPL: 303-411 AM / 301-427 PM LMA:MSA +1 818 354-1275 08:00 AM - 05:00 PM PST 20 Nov 2003. Navigation Requirements. - PowerPoint PPT Presentation
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• None specified, expected Navigation performance and capability adopted as requirement
– Must deliver S/C to 300 km flyby within 16 km (1-sigma) in B.T and B.R after last TCM (nominally at E-18h)
– Must know (but not control) Time of Encounter to 1,100 km or 180 sec (1-sigma) at E-8h
– This level of accuracy provides for:
• Collecting 500 particles 15 m or larger
• Gives a probability of serious impact to the spacecraft shielding 60 times less than Giotto at Halley Encounter or less than 2 %
• Enables the spacecraft to maintain carrier signal during Wild 2 Flyby
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Robust Wild 2 Encounter Navigation Design
• Maneuver startegy flexible to accommodate uncertainty in time of comet detection
• Success of Wild 2 Encounter and ease of operations dependent on two major factors:
– Optical Nav must detect Wild 2 before E-8d (DONE!)
• Expected to be seen by E-20d (already detected as of E-45d)
– At least two TCM’s must be performed during Approach
• One at E-10d (nominal), E-6d or E-2d (contingencies)
• Another at E-2d (nominal) or as late as E-18h or E-12h
• Option to do early TCM at E-30d if comet already detected
– Opportunity to correct Wild 2 ephemeris error early
– Not critical - ~80 m/s margin available to ensure 100 psia for ACS response during Encounter (another ~100 m/s in reserve thru EOM)
• Nav had implemented all timelines and interfaces during the Annefrank Encounter real-time operations and has retested for recent ORT
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Maneuver Design
• Maneuvers prior to E-2d to target to 150 km
– First TCM opportunity at E-30d (preliminary Delta-V ~1.5 m/s)
– Next TCM at E-10d (< 7 m/s in worst case, 275 km 1-sigma delivery error)
• Time-of-flight does not need to be controlled
– ~180 sec (1-sigma) worst case if uncorrected (Delta-V <3 m/s)
• Can slip as late as E-6d (<5.4 m/s with no TOF correction)
• Maneuver at E-2d to shift to final target at 300 km
– 70% probability within 90° roll about approach velocity vector
• Project desire to avoid > 90° turn away from Sun/Earth if possible
– Requires < 4 m/s to improve to <65 km, 1-sigma, delivery error)
– Time-of-flight not controlled (8-hr development timeline)
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Maneuver Design - Continued
• Maneuver may be performed at E-18h to clean up execution errors from E-2d TCM to improve targeting precision
– Will be performed only if statistically meaningful
• 28% probability not needed at all
• 22% probability beyond 90° roll about approach velocity vector
– Time-of-flight not controlled (8-hr development timeline)
– Can be slipped to as late as E-12h (< 2.3 m/s Delta-V and <24 km, 1-sigma, delivery error --> 13.5° bank angle at CA --> still supports MGA carrier only)
• GO/No-GO criteria in place for all Wild 2 approach maneuvers (tested at Annefrank and to be retested in upcoming ORT)
• Near-continuous DSN coverage in place with dual coverage within E±2h
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Maneuver Design - Contingencies
• TCM at E-30d can be cancelled
• TCM at E-10d can be slipped to E-6d or E-2d
• TCM at E-2d can be slipped to as late as E-12h
• As final option, up to 5 TCM’s pre-designed and tested to move away from comet in Earth-Wild 2 plane at E-6h
– Will be uplinked and stored on S/C before E-2d
– No attitude turns needed
– Designed to cover range of 100-1000 km of movement in B-plane at E-6h
– If desired, can be executed anytime after E-2d if desired to further augment movement away from Wild 2
• In the event of camera failure, flyby will be targeted to safe distance (>1,000 km) based on latest Wild 2 ephemeris knowledge
– Implemented by 1 of 5 stored TCM’s if desired as late as E-6h
– Nav stands down for the remainder of the Encounter period
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Navigation Readiness Status
• All operations, timelines and interfaces tested successfully at previous Annefrank Flyby– Annefrank too dim on Approach - Opt Nav performed with Flyby Annefrank/star
images• New ORTs have/will retest for last 2.5 days prior to Wild 2 Encounter
– Participants to be certified for operations by Project/MMO • Doppler and Ranging Only, no-Delta DOR implemented• No new observations, facilities, first-time events for Radio Nav and Maneuver• Workforce, Backups and Contingencies in place• Navigation Advisory Group (NAG) Readiness Review successfully completed
– 9 RFA’s considered• Reduced number and complexity of approach maneuvers where feasible and
adjusted staffing plans to reduce fatigue, meet CAN rqmts• Possible Opt Nav staffing at LMA still an open issue• All will be reconciled before Dec 15
– Agreed that Nav ready and qualified, pending final ORT, for Wild Encounter Operations
NOTE: All of above considered on call when not at JPL.* Will follow late evening schedule for at least two days prior to this period.† Individuals to be assigned by separate team chiefs (on SDU emergency contact list).** Periods shown can be on-call but require being on high alert and no more than 1/2 hour from JPL.
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Some Feedback from Navigation Peer ReviewSome Feedback from Navigation Peer Review
• Simplify Maneuver Plan √– TOF control not required (adjust encounter seq start time; allow schedule
for final two days to float ±1 hour, provided known by Dec 30)– Test of compressed (2.5 day) full TCM design entails schedule risk - not
needed (rely on existing 8-hour and 10-day TCM design templates)– Clarify requirements/rationale for avoiding off-sun rolls for later TCMs
• Adjust Staffing Plan √– Additional OD support recommended to avoid fatigue while still meeting
CAN requirements– Reduced MMNAV support (critical activities only)– Wider participation in meetings involving key decisions (include in ORT)
• Recommend backup OPNAV support at LMA in case JPL goes down (as additional measure to support selection of 1 of 5 “canned” maneuvers)
• Dual DSN coverage desirable for TCMs (probably not feasible given contention for DSN resources)
BU-3
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Nav Personnel Training and CertificationNav Personnel Training and Certification
• Thread Tests
– Starting condition prior to first TCM (TCM-10 on 12/3/03)
– Exercise interfaces among Nav subteams (OPNAV, Radio/OD, Maneuver; include Solar System Dynamics for second test)
– Repeat interactions through subsequent TCMs up to Wild 2 Encounter
• ORTs
– Annefrank Encounter ORT (10/31/02)
– TCM-12 and Preliminary Nucleus Tracking Update (Completed 11/5/03)
– TCM-13, TCM-14 Contingency and Final Nucleus Tracking Update (Planned for 12/9-10)
• Participation by all Nav personnel in recent activities provides for operational certification (endorsed by Stardust Project Mgr and MMO GNC Team Chief)
-30E d 3- -03Dec 1.54 2.58 706 189-10E d 23- -03Dec 1.75 3.42 270 113-2 ( - )E d roll only 31- -03Dec 1.98 3.88 65 113-18 ( - )E h roll only 2- -04Jan 0.78 1.56 16 113
--> 2TOTAL W 6.05 8.91 16 113
-10 ( )First TCM at E d Full DesignManeuver Epoch
( )UTC Mean
( / )m s95% tile( / )m s
( , Bmax km1 )s
LTF Ctrl † ( , sec 1 )s
-10E d 23- -03Dec 4.45 6.87 275 114-2 ( - )E d roll only 31- -03Dec 2.00 3.92 65 114-18 ( - )E h roll only 2- -04Jan 0.78 1.57 16 114
--> 2TOTAL W 7.23 10.52 16 114
-10 ( )First TCM at E d No LTF CorrectionManeuver Epoch
( )UTC Mean
( / )m s95% tile( / )m s
( , Bmax km1 )s
LTF Ctrl( , sec 1 )s *
-10 ( - )E d roll only 23- -03Dec 2.06 3.28 264 185-2 ( - )E d roll only 31- -03Dec 1.71 3.29 65 185-18 ( - )E h roll only 2- -04Jan 0.79 1.58 16 185
--> 2TOTAL W 4.55 6.83 16 185
-6 ( )First TCM at E d No LTF CorrectionManeuver Epoch
( )UTC Mean
( / )m s95% tile( / )m s
( , Bmax km1 )s
LTF Ctrl( , sec 1 )s *
-6 ( - )E d roll only 27- -03Dec 3.41 5.40 158 185-2 ( - )E d roll only 31- -03Dec 1.37 2.52 65 185-18 ( - )E h roll only 2- -04Jan 0.78 1.59 16 185
--> 2TOTAL W 5.56 8.07 16 185* , Dominated by comet ephemeris error without LTF correction† ( )Impact of TOF correction limited by OD error
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Final TCM GO/No-GO and Selection CriteriaFinal TCM GO/No-GO and Selection Criteria
E-2d (150 --> 300 km) and E-18h TCM
BU-9
E-6h TCM (Contingency)
E-18h Target Selection
+++300 km 350 km To Wild 2Target to point“above” Wild 2(< 90 deg Roll)
Target to point“above” Wild 2(90-180 deg Roll)
Remove out-of-plane error only(~90 deg Roll)*
GONo-GO++3sd ” Minimum safe distance” 2above Wild
( ):Decision Criterion if GO 1 5 “ ” ’Pick smallest of canned TCM s . which shifts location out by at least d
/To Earth Sun 2To WildTarget Point (“above” Wild 2)+*GO*No-GO+1sProjected Location and
• Can be used at E-6 hours to deal with last-minute anomaly or earlier (e.g., E-2d) if JPL disabled (e.g., earthquake)• Maneuver identified according to aimpoint shift expected at E-6 hours (effect would be 8 times greater at E-2d)• Select according to last JPL contact by default• If Op Nav support available at LMA, select according to estimate of OD uncert.• 100 and 1000 km shifts also recommended to round out set of 5 “canned” TCMs