Ocean Surface Topography Science Team Meeting

1
Geosat Follow-On Mission Status

• Ocean Surface Topography Science Team Meeting
• Venice, Italy March 16 - 18, 2006
• John Lillibridge
• NOAA Laboratory for Satellite Altimetry
• Gregg Jacobs Kirk Whitmer
• Naval Research Laboratory - Stennis Space Center

2
GFO Spacecraft Sensors

• Ku-band Altimeter
• Dual- Radiometer
• 4 GPS Receivers
• Doppler Beacon
• Laser Retro-reflector
• Fixed Solar Array
• Solid State Memory

3
Navy GFO Ground Segment
4
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

5
Altimetry Data Return
6
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 -gt 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

7
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

8
Near Real-Time AVISO Processing - GFO
Courtesy M-H. de Launay CLS
9
Near Real-Time Navy ADFC Processing
10
GFO Precise Orbit Statistics
11
GFO T/P Sea Surface Height

• SSH-MSS residuals 11 cm for GFO 10 cm for T/P
• Geocenter offsets applied (B. Beckley/GSFC)

12
Improved Mesoscale Sampling

• Pascual, A., Y. Faugere, 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.

13
East Australia Current Analysis - CSIRO
Courtesy D. Griffin -CSIRO
14
GFO contributes to GSLR records
15
Hurricane Katrina Altimetry
Scharroo, Smith and Lillibridge, EOS, 86(40), 2005
16
GFO Waveform Data Collection
17
NOAA Lab. for Satellite Altimetry GFO Site
18
Navy/NRL Data Access
19
U.S. GODAE Server - NAVO Products
20
AVISO/DUACS GFO Products
21
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 manufacturers 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