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Flight Dynamics

Flight Dynamics. Mark Beckman NASA/GSFC Code 595 August 16-17, 2005. Primary : Flight Dynamics Specification 431-SPEC-000063 Parent : LRO Mission Requirements Document 431-RQMT-000004 Two-Way : LRO Mission Concept of Operations 431-OPS-000042

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Flight Dynamics

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  1. Flight Dynamics Mark Beckman NASA/GSFC Code 595 August 16-17, 2005

  2. Primary: Flight Dynamics Specification 431-SPEC-000063 Parent: LRO Mission Requirements Document 431-RQMT-000004 Two-Way: LRO Mission Concept of Operations 431-OPS-000042 LRO Propulsion Subsystem Statement of Work and Specification 431-SOW-000017 Detailed Mission Requirements for the LRO Ground System 431-RQMT-000048 LRO Ground System Interface Control Document 431-ICD-000049 ACS Pointing Document TBD LRO ACS Spec TBD Document Tree

  3. Lunar Reconnaissance Orbiter (LRO)Flight Dynamics Level 2 Flow DownKey Requirements Level 2 Req. Level 3: Requirements Concept/Compliance Paragraph Requirement MRD-24 MRD-3 FDS-2.1 LRO shall be launched on a 7925H-9.5 launch vehicle with a coast time of up to 68 (TBD) minutes. Short coast northern TTIs may require coast time up to 68 min. MRD-24 MRD-3 FDS-2.2.1 LRO shall have one daily launch opportunity that consists of a short coast minimum energy direct transfer to the moon. Daily opportunities further reduced with lighting constraint. MRD-11 FDS-2.4 LRO shall insert into lunar orbit over the lunar southern pole and have an initial southern argument of periselene. (TBR) May add northern insertion if analysis shows dV improvement or additional daily launch opportunity required. MRD-4 FDS-2.2.2 The LRO launch window shall be constrained such that the nominal spin direction at separation is within 15 deg of either the Sun or anti-Sun. Lighting constraint at spacecraft separation.

  4. Lunar Reconnaissance Orbiter (LRO)Flight Dynamics Level 2 Flow DownKey Requirements Level 2 Req. Level 3: Requirements Concept/Compliance Paragraph Requirement MRD-146 FDS-2.4 LRO shall maintain a minimum altitude of 100 km (TBD) during LOI phase. Safe altitude. MRD-146 FDS-2.4.1 LRO shall maintain a periselene of greater than 200 km (TBD) after LOI1. Consistent with frozen orbit for commissioning. MRD-146 MRD-10 MRD-11 FDS-2.4.2 LRO shall perform up to eight (TBD) LOI maneuvers to insert the spacecraft into the commissioning orbit. Minimizes finite burn loses. MRD-3 MRD-25 MRD-10 FDS-2.2.2 LRO shall perform an MCC1 maneuver prior to L+24 (TBD) hours to correct for LV dispersions. Additional dV saved by performing earlier.

  5. Lunar Reconnaissance Orbiter (LRO)Flight Dynamics Level 2 Flow DownKey Requirements Level 2 Req. Level 3: Requirements Concept/Compliance Paragraph Requirement MRD-11 FDS-5.0 The commissioning orbit shall be a frozen orbit at 30x216 km altitude and a 270 deg argument of periapsis. No stationkeeping dV required. MRD-146 MRD-12 FDS-4.0 LRO shall perform a stationkeeping cycle approximately every 27.4 days. Eccentricity, argument of periapsis and longitude repeat every month within the separation between consecutive groundtracks. MRD-146 MRD-12 FDS-4.1.3 LRO's stationkeeping shall target periselene in the southern hemisphere 50% of the time. Stationkeeping strategy C complies. MRD-12 FDS-4.1.2 The primary mission shall be conducted in a circular mapping orbit with a nominal altitude of 50 +/- 20 km (altitude is measured to mean lunar surface). Altitude control band dictates frequency of stationkeeping maneuvers.

  6. Lunar Reconnaissance Orbiter (LRO)Flight Dynamics Level 2 Flow DownKey Requirements Level 2 Req. Level 3: Requirements Concept/Compliance Paragraph Requirement MRD-147 FDS-3.1.6 LRO maneuvers shall be performed in view of S-band tracking stations. May not be possible for all of LOI1 MRD-41 FDS-3.1.4 LRO shall have a minimum Orbit Determination Accuracy of 500/18 m (total position RMS/radial RMS, 1-sigma, post-processed). Consistent with existing S-band measurements and current lunar gravity model.

  7. Moon at encounter Cis-lunar transfer 4 day transfer Launch C3: –2 km2/s2 Lunar Orbit 1-day Earth Sun direction Nominal Cis-lunar Trajectory Solar Rotating Coordinates Transfer Trajectory

  8. Mission Orbit

  9. Ground station tracking certification One new antenna (18m at White Sands) Four antennas (Australia, Belgium, Hawaii, Sweden) Flight Dynamics Facility (FDF) certifies tracking station measurement accuracy End-to-End tests Flight Dynamics Simulations Contingency plans Anomalies Verification

  10. Only a few key Level 2 driving requirements All well understood Many derived Level 3 requirements Some in flux as spacecraft design/con ops solidify Flight Dynamics Specification details all mission design and navigation References to all analysis documents Flight Dynamics is ready to proceed to PDR Summary

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