Transcript Document

Flight Dynamics
Mark Beckman
NASA/GSFC Code 595
August 16-17, 2005
NASA’s Goddard Space Flight Center
20b - 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 431SOW-000017
– Detailed Mission Requirements for the LRO Ground System 431RQMT-000048
– LRO Ground System Interface Control Document 431-ICD-000049
– ACS Pointing Document TBD
– LRO ACS Spec TBD
NASA’s Goddard Space Flight Center
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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 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.
NASA’s Goddard Space Flight Center
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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 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.
NASA’s Goddard Space Flight Center
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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 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.
NASA’s Goddard Space Flight Center
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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
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, postprocessed).
Consistent with existing Sband measurements and
current lunar gravity model.
NASA’s Goddard Space Flight Center
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Transfer Trajectory
Moon at encounter
Cis-lunar transfer
4 day transfer
Launch C3: –2 km2/s2
Sun direction
Lunar Orbit
1-day
Earth
Nominal Cis-lunar Trajectory
Solar Rotating Coordinates
NASA’s Goddard Space Flight Center
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Mission Orbit
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Verification
• 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
NASA’s Goddard Space Flight Center
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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
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