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Transcript of Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting GPS-Based...
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting
GPS-Based Precise Orbit Determination: Jason-1 Status
Willy Bertiger, Bruce Haines, Shailen DesaiJet Propulsion Laboratory, California Inst. of Tech., Pasadena CA
Pascal WillisInstitut Geographique National/Institut de Physique du Globe de
Paris, France
March, 2007
Ocean Surface Topography Science Team Meeting
Hobart, Australia
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting
• Better Understanding of GPS Phase Centers based on GRACE Dynamics and Calibrations
• JEM03 – GRACE Static Gravity Field (vs GGM02C)
– AOD1B Release 4 ( vs none )
• Sub-daily density variations in atmosphere, gravitational effect
• ITRF2005 (vs ITRF2000)
Release 07a Incremetal Changes Relative to Release 06b (March 2006)
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting
GRACE As An Antenna Instrument For GPS Trans. Calibration
• Daily precise orbit solutions spanning two years (2004–06)
• One s/c at a time• Dynamical POD to preserve link
between scale and GM
– CD and 1 cpr acc. reset every rev. per UT/CSR approach
• GPS ephemeris and clock offsets fixed to precise values (JPL/IGSAC)
• GRACE antenna a priori PCV model from anechoic chamber:
• 30-sec GPS data– Carrier (LC) only and carrier + code (LC +
PC) solutions performed. No Z apriori• Postfit residuals binned according to az/el of
transmitters.– Least-squares fit to antenna map– Iterate until converged (12XLC, 5XLC/PC)
–15
0
15mm
0
December 11, 2006 BJH 4Fall AGU 2006
mm
-10
+10
GRACE-Based Phase-Center Variation (PCV)
Maps Reveal GPS Antenna Elements
-12
+18
mm
Block II/IIA PCV
Block IIR-B(M) PCV
-10
+10
mm
Block IIA Antenna(Mader and Czopek, 2002)
Block IIR-A PCV
PCV for Ionosphere-free Carrier (LC) with Mean Offset Removed
December 11, 2006 BJH 5Fall AGU 2006
T/P Radial Antenna Offset Explained
-100
-50
0
50
100
-12
-8
-4
0
4
8
12
1994.0 1996.0 1998.0 2000.0 2002.0 2004.0 2006.0
Time Series of T/P and Jason-1 Radial Antenna Offset EstimatesNoneIGSJPLBCDBCD
Nominal (Gipsy) ModelGRACE-Based GPS PCV Maps
mm
ppb
Year
TOPEX/Poseidon Jason-1
GRACE Data SpanUsed In
PCV Maps
D
-8.2953701Minimum
8.5058155Maximum
0.60300648Sum
19Points
0.031737183Mean
1.1129774Median
4.6419038RMS
4.7689914Std Deviation
22.743279Variance
1.0940817Std Error
-0.039184551Skewness
-0.92282638Kurtosis
Slope = +3.7 ± 0.1 mm/yr
Slope = +0.1 ± 0.1 mm/yr
Bias = +55.6 ± 0.8 mm
B
48.259182Minimum
60.715157Maximum
1056.7383Sum
19Points
55.617803Mean
55.645386Median
55.716286RMS
3.4020173Std Deviation
11.573722Variance
0.78047629Std Error
-0.39930782Skewness
-0.57790671Kurtosis
Bias = +0.0 ± 1.1 mm
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting
JASON Calibration (3 Iterations)
• Dynamic JASON runs 2002-JAN-14 to 2006-JAN-01• Very similar in appearance to release 06b (last year)
Phase Code
-400 400-30 30
mm mm
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting
Release 07a Comparison with GDRB
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting
GDRB-ITRF2000, Rel07a/GSFC-ITRF2005
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting
Reference Frame, Differences with GSFC SLR/DORIS
Model Errors, GPS?Some Pattern with GDRB
-15
-10
-5
0
5
10
15
20 -100
-50
0
50
1000 50 100 150
X MeanY MeanZ Mean
BetaM
ea
n D
iffe
ren
ce
(m
m)
Be
ta (d
eg
ree
s)
Cycle
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting
Geographic Radial Comparison to GDR-B
-16 160
mmmm
Cycles 21-39 Cycles 150-169
RMS: 1.9 mm RMS: 3.5 mm
-16 160
ITRF2000 - 05 Z ~ 11.5ITRF2000 - 05 Z ~ 5.1
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting
Geographic Radial Comparison to GSFC SLR+DORIS
-16 160
mmmm
Cycles 21-39 Cycles 150-169
RMS: 2.9 mm RMS: 3.4 mm
-16 160
GSFC and JPL Rel07a both use ITRF2005
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting
Release 06b - Release 07a
mm
Cycles 141-146
RMS: 1.8 mm
-16 160
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting
Xover Tests
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting
Xover Tests
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting
Summary
• Incremental Changes to JPL GPS orbits– Gravity Field, Phase Centers, AOD1B, ITRF2005
• Comparison with GDR-B– Close Performance Measured by crossovers– Slightly better comparison to R06b, Z shift ITRF2005
• Reference Frame Issues ~ cm (Comparison with GSFC SLR/DORIS)– Antenna, Force Models?
• Future Enhancements– Use Solar Panel Quaternions to improve solar pressure– Test other gravity fields, apply time varying solid earth
gravity ( fit to monthly fields )– Improved Albedo Models– Re-tune POD strategy
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting
Backups
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting
Jason Phase Simulation
-30 +30mm
-30 +30
• Simulation/Limitations• Bus Structure -- Flat Plates • Other GPS Antenna -- Disk• Radiometer -- Disk
Empirical 2XSimulation
December 11, 2006 BJH 18Fall AGU 2006
GPS Transmitter PCV Maps Explain Anomalous Estimated Radial Antenna
Offsets for Jason-1
-50
0
50
-8
-6
-4
-2
0
2
4
6
8
2002.0 2003.0 2004.0 2005.0 2006.0
Time Series of Jason-1 Radial Antenna Offset EstimatesNoneIGSJPLBCD
PPB
PPB
PPB
mm ppb
Year
SVN45SVN47
SVN59SVN60 SVN61SVN56 SVN53
ppb/yrmm/yrppbmmAPPROACH
+0.5+3.7+5.7 +44 Gipsy Nominal (No Maps) +0.0+0.1–2.4 –19 GRACE-Based PCV Maps
BIAS (2004.5) DRIFT
y = m1 + m2*(M0-2004.5)
ErrorValue
0.09989344.073m1
0.0793083.6713m2
NA13240Chisq
NA0.80499R
y = m1 + m2*(M0-2004.5)
ErrorValue
0.099305-31.07m1
0.0788412.4847m2
NA13085Chisq
NA0.67854R
y = m1 + m2*(M0-2004.5)
ErrorValue
0.098676-18.635m1
0.0783410.10805m2
NA12919Chisq
NA0.040391R
y = m1 + m2*(M0-2004.5)
ErrorValue
0.0129735.7237m1
0.01030.47679m2
NA223.31Chisq
NA0.80499R
y = m1 + m2*(M0-2004.5)
ErrorValue
0.012897-4.035m1
0.0102390.32269m2
NA220.69Chisq
NA0.67854R
y = m1 + m2*(M0-2004.5)
ErrorValue
0.012815-2.4201m1
0.0101740.014032m2
NA217.9Chisq
NA0.040391R
Jason-1 Yaw Steering
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting
Improvements Over JPL Release 4, Nov. 2005
Release 04b Release 6.0b
SLR Mean Monthly Variance (mm2)
136 +/- 46 125 +/- 40
SLR Median Monthly RMS (mm)
11.2 10.7
Residuals 65% have smaller monthly residuals
Mean of Daily Radial RMS ( Dynamic – Reduced Dyn) (mm)
10.1 (1376 days) 9.1 (1374 days)
Improved Antenna, Force Models => Re-tune Stochastics, Data weight, Outlier Detection
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting
R06b Comparison to GDR
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting
Reference Frame GDRB vs Rel07b
Hobart Australia March 2007Willy Bertiger Ocean Surface Topography Science Team Meeting
Release 06b - Release 07a Cycle Mean Z