# Presentation: 946360

## Geosat Follow-On Cal/Val

- Briefing to the NPOESS
- Integrated Program Office
*February 2, 2004*
- John Lillibridge &
- Bob Cheney
*NOAA/NESDIS/ORA*
*Laboratory for Satellite Altimetry*

## Spacecraft & Sensors

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

## A Brief History

- Launch: 2/10/1998 from Vandenberg AFB
- 6th Anniversary approaching; 8-year nominal lifetime
- Initial hardware difficulties
- Onboard CPU resets
- GPS receivers failed
- Loss of primary orbit determination system
- Loss of precision time-tagging
- Ground-based time-tag unit at NAVSOC: June, 1999
- CPU reset problems solved: November, 1999
- Navy acceptance: November 29, 2000

## Altimetry Data Return

- Start of GDRs

- Navy Acceptance

- Time-tag Unit

- Momentum Wheel
- Anomaly

## Core Activities - U.S. Navy

- SPAWAR
- Program management
- Navy Cal/Val team - CSC contractors
- NAVSOC
- Satellite Command/Control & Data telemetry
- Operational Doppler orbits
- NAVO/NRL
- Payload Operations Center - ADFC
- Near real-time altimetry - GODAE server
- DoD data requests

## Core Activities - NASA & NOAA

- 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 Geophysical Data Records (GDRs)
- Near real-time Interim GDR
- Civilian Data Requests (Foreign & National)
- Funding OSU Cal/Val team & GSFC Orbits
- Funded CLS for GFO-specific sea-state bias model
- Data archive at NODC

## Navy/SPAWAR Cal/Val

- Precision Time-tag Monitoring
- Incentive Fee to Ball Aerospace:
- Cycle by cycle data coverage
- Radar altimeter noise-floor determination
- Water Vapor Radiometer noise determination

## Ultra-Stable Oscillator Drift

- ƒ/ƒ ~ t/t ~ h/h ~ 10-7 (0.1 ppm)
- _Doppler Frequency_	ƒ: 	400 MHz	ƒ: 	40 Hz
- _Record Spacing_	t:	0.98 sec	t:	0.1 sec
- _Range Correction_	h:	800 km	h:	8 cm

## Ultra-Stable Oscillator Clock Drift

## NASA Wallops Cal/Val

- Altimeter instrument performance
- Validate instrumental corrections to range, AGC, SWH
- Distribute cal/val data records
- Monitor internal calibration mode & provide corrections
- Daily Science Data sanity plots
- Windspeed monitoring
- Attitude Boresight “ABCAL” maneuver analysis

## Attitude Adjustment

- Mean Off-Nadir angle ~ 0.24° until Feb.’02
- Attitude ~ 0.08° now
- Current SDR algorithm “clips” Attitude2

## Greenland Heights vs. ETOPO2

- Deviations relative to Geoid+Topography
- -40 meter interior offset
- Compare with DTM2000
- No waveform retracking

## Ohio State Cal/Val

- Navy & NOAA products evaluated
- Sea surface height residuals
- Water vapor correction validation
- Orbit error estimates from crossovers

## 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

## SSH after orbit error removal

## GFO & T/P Sea Surface Height

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

## NOAA GFO GDR Datasets

- Based on final POE laser orbits
- State of the Art Corrections
- Cycles 37 - 104 on three DVDs
- January, 2000 - March, 2003
- Cycles 105 - 118 via ftp
- March - November, 2003
- < 10 cm SSH Variability
- Cycles 119... with MOE orbits
- Daily IGDR files in 3 days NRT

## NOAA Funding for GFO

- $80K	NASA/GSFC Orbit Determination
- $50K	Ohio State Cal/Val Team
- $35K	CNES/CLS Sea-State Bias Model
- $65K	NRC Post Doc - Remko Scharroo
- $230K	excluding salaries & NODC support

## Momentum Wheel Anomaly

## CODE Ionosphere Model

- GPS based Global Ionosphere Model
- Presently still near peak in solar activity
- Operational TEC grids via mirror scripts

## Land/Ice/Lake Coverage