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Venice 2006 OSTST 16-Mar-2006GFO Mission & Status #
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Ocean Surface Topography Science Team MeetingVenice, Italy: March 16 - 18, 2006
John LillibridgeNOAA Laboratory for Satellite Altimetry
Gregg Jacobs & Kirk WhitmerNaval Research Laboratory - Stennis Space Center
Geosat Follow-On Mission & Status
Venice 2006 OSTST 16-Mar-2006GFO Mission & Status #
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GFO Spacecraft & Sensors
• Ku-band Altimeter
• Dual-ƒ Radiometer
• 4 GPS Receivers
• Doppler Beacon
• Laser Retro-reflector
• Fixed Solar Array
• Solid State Memory
Venice 2006 OSTST 16-Mar-2006GFO Mission & Status #
3
Navy GFO Ground Segment
Venice 2006 OSTST 16-Mar-2006GFO Mission & Status #
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A Brief History
• Launch: 10-Feb-1998 from Vandenberg AFB– 8-year nominal lifetime, celebrated 8th anniversary in 2006
• Initial hardware difficulties– Onboard CPU resets during first two years– GPS receivers failed in spite of 4-unit redundancy
• Loss of primary orbit determination system
• Loss of precision time-tagging
• Ground-based time-tag unit at NAVSOC: June, 1999• Precision orbit determination based on SLR tracking• CPU reset problems solved: November, 1999• Navy acceptance: November 29, 2000• Momentum wheel anomalies - temperature sensitivity
Venice 2006 OSTST 16-Mar-2006GFO Mission & Status #
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Altimetry Data Return
Navy Acceptance
Start of GDRs
Momentum Wheel Anomaly
Payloads off - Thermal Issues
Venice 2006 OSTST 16-Mar-2006GFO Mission & Status #
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Interagency Participation
• U.S. Navy
– SPAWAR• Program management• Navy Cal/Val team
– NAVSOC• Satellite Command/Control• Data Telemetry• Operational Doppler orbits
– NAVO/NRL - Stennis• Payload Operations Center - ADFC• Near real-time altimetry -> GODAE• Military data requests
• NASA
– Wallops Flight Facility• Instrument performance monitoring & Cal/Val
– Goddard Space Flight Center• Precise Orbit Determination from laser ranging • Ice-sheet monitoring via altimeter waveforms
• NOAA
– Final Science-quality GDRs– Near real-time IGDRs– Civilian Data Requests (Foreign & National)– Funding OSU Cal/Val team & GSFC Orbits– Funded CLS for sea-state bias model
Venice 2006 OSTST 16-Mar-2006GFO Mission & Status #
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European Partners
• CNES - Corsica absolute calibration• CLS - Real-time “DUACS” system
– Validation of all corrections– Editing thresholds and engineering flags– Sea surface height, SWH, Wind & Attitude
• S.O.S. (U.K.) - SWH/Wind Buoy validation
Venice 2006 OSTST 16-Mar-2006GFO Mission & Status #
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Near Real-Time AVISO Processing - GFOC
ross
over
RM
S (
cm)
Before orbit error reduction
After orbit error reduction
Courtesy:M-H. de Launay
CLS
Venice 2006 OSTST 16-Mar-2006GFO Mission & Status #
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Near Real-Time Navy ADFC ProcessingC
ross
over
rm
s (m
)
Venice 2006 OSTST 16-Mar-2006GFO Mission & Status #
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GFO Precise Orbit Statistics
Venice 2006 OSTST 16-Mar-2006GFO Mission & Status #
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GFO & T/P Sea Surface Height
• SSH-MSS residuals: 11 cm for GFO; 10 cm for T/P• Geocenter offsets applied (B. Beckley/GSFC)
Venice 2006 OSTST 16-Mar-2006GFO Mission & Status #
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Improved Mesoscale Sampling
Pascual, A., Y. Fauge`re, G. Larnicol, and P.-Y. Le Traon (2006), Improved description of the ocean mesoscale variability by combining four satellite altimeters, Geophys. Res. Lett., 33, 2006.
Venice 2006 OSTST 16-Mar-2006GFO Mission & Status #
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East Australia Current Analysis - CSIRO
Courtesy: D. Griffin -CSIRO
Venice 2006 OSTST 16-Mar-2006GFO Mission & Status #
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GFO contributes to GSLR records
Venice 2006 OSTST 16-Mar-2006GFO Mission & Status #
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Hurricane Katrina & Altimetry
Scharroo, Smith and Lillibridge, EOS, 86(40), 2005
Venice 2006 OSTST 16-Mar-2006GFO Mission & Status #
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GFO Waveform Data Collection
Venice 2006 OSTST 16-Mar-2006GFO Mission & Status #
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NOAA Lab. for Satellite Altimetry GFO Site
Venice 2006 OSTST 16-Mar-2006GFO Mission & Status #
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Navy/NRL Data Access
Venice 2006 OSTST 16-Mar-2006GFO Mission & Status #
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U.S. GODAE Server - NAVO Products
Venice 2006 OSTST 16-Mar-2006GFO Mission & Status #
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AVISO/DUACS GFO Products
Venice 2006 OSTST 16-Mar-2006GFO Mission & Status #
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Continuing GFO Operations
• GFO has reached its nominal 8-year lifetime
• Navy, NOAA, & NASA will continue operations as long as possible
• Two significant hardware issues to face:
– Thermal sensitivity of reaction wheels
• Wheel #1 taken offline: may still be viable, but requires further study
• Wheel #3 sensitive to overheating
– Reduced operations when orbit in “full-sun” orientation
– Battery aging effects
• Will reach manufacturer’s spec. on charge/discharge cycles this year
• During orbital eclipse voltages approach undervoltage limit
– Direct Downlink mode has been terminated (transmitter off)
– Implement ‘one-failed-cell’ battery mode to lower UV limits
– Place altimeter in standby for portion of eclipse (each rev…)
– Power off Water Vapor Radiometer for extended periods of time