1. Monitoring Jason-1 and TOPEX/POSEIDON from a California Offshore Platform: Latest Results from the Harvest Experiment
Bruce Haines and Shailen Desai
Jet Propulsion Laboratory, California Inst. of Tech., Pasadena CA
George Born
University of Colorado, Boulder
Steve Gill
NOAA National Ocean Service, Silver Spring MD
March 12–15, 2007
Ocean Surface Topography Science Team Meeting
Hobart, Australia

2. Motivation
How do we best calibrate sea-level record at the 1 mm/level?
Geographically correlated errors in both the bias and rate
What are the sources of the errors?
March 12-15, 2007
Ocean Surface Topography Science Working Team Meeting
Cal/Val Splinter Session

3. Map of Harvest Vicinity
NOAA
BUOYS
SCRIPPS
BUOY
HARVEST
March 12-15, 2007
Ocean Surface Topography Science Working Team Meeting
Cal/Val Splinter Session

4. HARVEST EXPERIMENT WVR (JPL) GPS ANTENNA (JPL) + 54 m MET SENSORS
LASER
SENSOR
(CU)
+ 27 m
EQUIP SHED
(NEW VSAT DISH)
Point Arguello, CA
+ 6 m
BUBBLER2 (NOAA)
BUBBLER1 (NOAA)

5. 14 Years of Continuous GPS Monitoring
March 12-15, 2007
Ocean Surface Topography Science Working Team Meeting
Cal/Val Splinter Session

6. Harvest Closure Analysis (SSH Bias)
Nominal Models for Altimeter Leg in Closure Equation
Some extended analysis:
Examine retracked ALT-B data (cycles 290–365)
Revisit legacy data (Jason GDR-A and T/P MGDR) with new in situ models
Evaluate preliminary ITRF2005-based solutions for T/P, Jason-1 orbits and platform position
March 12-15, 2007
Ocean Surface Topography Science Working Team Meeting
Cal/Val Splinter Session

7. Long-Term Sea-Surface Height Bias Estimates
Nominal (T/P: MGDR-B+TMR+GSFC TVG; Jason-1: GDR-B)
March 12-15, 2007
Ocean Surface Topography Science Working Team Meeting
Cal/Val Splinter Session

8. Long-Term Sea-Surface Height Bias Estimates
Legacy Products (T/P MGDR; Jason GDR-A)
March 12-15, 2007
Ocean Surface Topography Science Working Team Meeting
Cal/Val Splinter Session

9. Calibration of Vertical Wet Path Delay at Harvest
USING DATA FROM HARVEST GPS RECEIVERS
Uncalibrated
(MGDR TMR &
GDR-A JMR)
Calibrated
(Repro. TMR &
GDR-B JMR)
March 12-15, 2007
Ocean Surface Topography Science Working Team Meeting
Cal/Val Splinter Session

10. Jason-1 Calibration Phase: Formation Flight with TOPEX/Poseidon (Jan
Jason-1 Calibration Phase: Formation Flight with TOPEX/Poseidon (Jan. – Aug. 2002)
Satellites trace out same ground track
Jason-1 leads T/P by 70 s (~400 km)
Presents unique opportunity to cross calibrate independent measurements systems.
Enables observation of the same spot on the ocean surface under nearly identical environmental and ocean conditions.
March 12-15, 2007
Ocean Surface Topography Science Working Team Meeting
Cal/Val Splinter Session

11. Jason-1 Verification Phase: Dual Overflight Results
March 12-15, 2007
Ocean Surface Topography Science Working Team Meeting
Cal/Val Splinter Session

12. T/P (ALT-B) Retracked Data
Relative Ku-Band Range During Jason-1 Verification Phase:
(HORBIT – RKu)JASON — (HORBIT – RKu)TOPEX
SSH Bias (ALT–B) for Repeat Cycles 290–365 (RGDR Release)
Strategy No
Mean
Median 
Nominal 34
–3 ± 6 –8
LSE
+3 ± 6 +4 36
Map
–39 ± 9
–56 52
March 12-15, 2007
Ocean Surface Topography Science Working Team Meeting
Cal/Val Splinter Session

13. Harvest Summary Jason-1 SSH biased (high) by 11 cm.
Contrasts with +15 cm bias in legacy (GDR-A) data at epoch (2002.0)
Jason-1 SSH drift (< 1 mm/yr) statistically insignificant
Contrasts with large –10 mm/yr drift in legacy (GDR-A) data
Re-calibrated JMR and improved POE responsible for improvement
T/P SSH biases small
< 1 cm bias for ALT-A, ALT-B at epoch
Poseidon-1 bias (–2 cm) slightly significant
Slight drifts (< 1–2 mm/yr) in T/P altimeter measurement systems
Questionable statistical significance from Harvest data alone
New TMR wet path delay correction stable
Remaining drift << 1 mm/yr
Slight residual drift in JMR–GPS
–2.6 mm/yr at Harvest; not observed in global GPS results (Desai et al.)
ITRF2005 will affect SSH stability estimates at 1 mm/yr level (preliminary).
Mostly from change in estimated platform position; orbit effect small at Harvest lat.
Mixed results for T/P retracked data
LSE comparable to nominal, but fewer overflight samples survive (high o).
High scatter for MAP estimates.
March 12-15, 2007
Ocean Surface Topography Science Working Team Meeting
Cal/Val Splinter Session

14. Backup Slides
March 12-15, 2007
Ocean Surface Topography Science Working Team Meeting
Cal/Val Splinter Session

15. Geographically Correlated Errors Jason-1 — T/P SSH (Tandem Verification Phase)
Harvest
Corsica
Assumptions
Jason-1 GDR-B replaces GDR-A
New GSFC T/P orbit (GGM02C) replaces MGDR POE
Global TMR drift correction applied
Topex ALT-B retracked range NOT used (next step)
ASC. TRACKS s = 16 mm
(mm)
DES. TRACKS s = 12 mm
BASS STRAIT
(mm)
March 12-15, 2007
Ocean Surface Topography Science Working Team Meeting
Cal/Val Splinter Session

16. Geographically Correlated Errors Remain  SSH Bias: Harvest vs
Geographically Correlated Errors Remain  SSH Bias: Harvest vs. Global Results
March 12-15, 2007
Ocean Surface Topography Science Working Team Meeting
Cal/Val Splinter Session

17. Calibration of Ionosphere Delay at Harvest
USING DATA FROM JPL GIM SOLUTION
March 12-15, 2007
Ocean Surface Topography Science Working Team Meeting
Cal/Val Splinter Session

18. Jason-1 SSH Stability Estimates
Jason-1 GDR (Ver. A)
+ GPS Orbit
+ GPS Orbit
+ GPS Wet Path Delay
+ GPS Orbit
+ Calibrated JMR data
March 12-15, 2007
Ocean Surface Topography Science Working Team Meeting
Cal/Val Splinter Session

19. Conditions at Harvest are Typical of Open Ocean
March 12-15, 2007
Ocean Surface Topography Science Working Team Meeting
Cal/Val Splinter Session

20. Periodicities in the Platform Height
March 12-15, 2007
Ocean Surface Topography Science Working Team Meeting
Cal/Val Splinter Session

21. Geographically Correlated Radial Orbit Error Rate
GDR Orbit — JPL GPS: Radial Rate for Cycles 1–90
All Tracks
Descending Tracks
Ascending Tracks
Corsica:
Rate = –0.5 mm/yr
Bass Strait:
Rate = –4.9 mm/yr
Harvest:
Rate = –6.6 mm/yr
–10 10
mm/yr
March 12-15, 2007
Ocean Surface Topography Science Working Team Meeting
Cal/Val Splinter Session

22. GPS Antenna Phase Center Variations
Postfit tracking residuals are binned by az/el (Hurst and Bar-Sever, 1998)
Both carrier phase and pseudorange
Resulting antenna PCV maps used in precise point positioning
Mitigate multipath and other systematic GPS errors
Maps reduce amplitude of residual annual signal from 5.5 mm to 3.6 mm
March 12-15, 2007
Ocean Surface Topography Science Working Team Meeting
Cal/Val Splinter Session

23. CU Laser Sea Level System
March 12-15, 2007
Ocean Surface Topography Science Working Team Meeting
Cal/Val Splinter Session

24. CU Laser Sea Level System
Installed on 12 m deck, upstream of platform legs.
In operation since March, 2002 (precise survey pending).
Data used to mitigate Digibub sea-state errors.
Agreement between NOAA and CU sea level (after removing sea-state effect) is ~1.7 cm.
March 12-15, 2007
Ocean Surface Topography Science Working Team Meeting
Cal/Val Splinter Session

25. CU Sea Level System March 12-15, 2007
Ocean Surface Topography Science Working Team Meeting
Cal/Val Splinter Session

26. Error Budget: Bias March 12-15, 2007
Ocean Surface Topography Science Working Team Meeting
Cal/Val Splinter Session

27. Jason-1 – T/P Sea Surface Height: Descending Tracks
Formation Flying Phase
Jason-1 GDR: Cycles 1–21
T/P MDGR + TMR Drift Correction: Cycles 344–364
SOUTH
Mean = mm
s = 10.8 mm
TROPICS
Mean = mm
s = 10.7 mm
NORTH
Mean = mm
s = 12.0 mm
GLOBAL
Mean = mm
s = 12.1 mm mm

28. Jason-1 – T/P Sea Surface Height: Ascending Tracks
Formation Flying Phase
Jason-1 GDR: Cycles 1–21
T/P MDGR + TMR Drift Correction: Cycles 344–364
SOUTH
Mean = mm
s = 10.9 mm
TROPICS
Mean = mm
s = 11.4 mm
NORTH
Mean = mm
s = 12.7 mm
GLOBAL
Mean = mm
s = 15.9 mm mm