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STARDUST Project CRITICAL EVENTS READINESS
REVIEW COMET P/WILD 2 ENCOUNTER NAVIGATION Kenne
th E. Williams
JPL 303-411 AM / 301-427 PM LMA MSA 1 818
354-1275 0800 AM - 0500 PM PST 20 Nov 2003
2
Navigation Requirements

• 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 mm 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 TCMs 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

4
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 (lt 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 lt3 m/s)
• Can slip as late as E-6d (lt5.4 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 gt 90 turn away from
  Sun/Earth if possible
• Requires lt 4 m/s to improve to lt65 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 (lt 2.3 m/s
  Delta-V and lt24 km, 1-sigma, delivery error --gt
  13.5 bank angle at CA --gt 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 E2h

6
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 TCMs 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 (gt1,000 km) based on
  latest Wild 2 ephemeris knowledge
• Implemented by 1 of 5 stored TCMs 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 RFAs 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

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Backup Charts
BU-1
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Navigation Staffing Plan
BU-2
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Some Feedback from Navigation Peer Review

• Simplify Maneuver Plan v
• 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 v
• 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 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)

BU-4
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Navigation External Interfaces
BU-5
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Navigation Internal Interfaces
BU-6
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Communications for 300 km Flyby
BU-7
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Selected Maneuver Analysis Results
BU-8
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Final TCM GO/No-GO and Selection Criteria
E-2d (150 --gt 300 km) and E-18h TCM
E-6h TCM (Contingency)
E-18h Target Selection
BU-9
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Contingency Maneuver (E-6 Hours) for Operational
Backup

• 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

BU-10