Flight Dynamics Mark Beckman NASAGSFC Code 595 August

Flight Dynamics Mark Beckman NASA/GSFC Code 595 August 16 -17, 2005 NASA’s Goddard Space Flight Center 20 b - 1

Document Tree • 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 NASA’s Goddard Space Flight Center 20 b - 2

Lunar Reconnaissance Orbiter (LRO) Flight Dynamics Level 2 Flow Down Key Requirements Level 2 Req. Level 3: Requirements Paragraph Concept/Compliance Requirement MRD-24 MRD-3 FDS-2. 1 LRO shall be launched on a 7925 H-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 d. V 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. NASA’s Goddard Space Flight Center 20 b - 3

Lunar Reconnaissance Orbiter (LRO) Flight Dynamics Level 2 Flow Down Key Requirements Level 2 Req. Level 3: Requirements Paragraph Concept/Compliance 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 LOI 1. 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 MCC 1 maneuver prior to L+24 (TBD) hours to correct for LV dispersions. Additional d. V saved by performing earlier. NASA’s Goddard Space Flight Center 20 b - 4

Lunar Reconnaissance Orbiter (LRO) Flight Dynamics Level 2 Flow Down Key Requirements Level 2 Req. Level 3: Requirements Paragraph Concept/Compliance Requirement MRD-11 FDS-5. 0 The commissioning orbit shall be a frozen orbit at 30 x 216 km altitude and a 270 deg argument of periapsis. No stationkeeping d. V 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. NASA’s Goddard Space Flight Center 20 b - 5

Lunar Reconnaissance Orbiter (LRO) Flight Dynamics Level 2 Flow Down Key Requirements Level 2 Req. Level 3: Requirements Paragraph Concept/Compliance 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 LOI 1 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, postprocessed). Consistent with existing Sband measurements and current lunar gravity model. NASA’s Goddard Space Flight Center 20 b - 6

Transfer Trajectory Moon at encounter Cis-lunar transfer 4 day transfer Launch C 3: – 2 km 2/s 2 Sun direction Lunar Orbit 1 -day Earth Nominal Cis-lunar Trajectory Solar Rotating Coordinates NASA’s Goddard Space Flight Center 20 b - 7

Mission Orbit NASA’s Goddard Space Flight Center 20 b - 8

Verification • Ground station tracking certification – One new antenna (18 m 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 NASA’s Goddard Space Flight Center 20 b - 9

Summary • 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 NASA’s Goddard Space Flight Center 20 b - 10