POD/Geoid Splinter Summary

26
POD/Geoid Splinter Summary OSTS Meeting, Hobart 2007

description

POD/Geoid Splinter Summary. OSTS Meeting, Hobart 2007. POD report Revised orbit error budget. Contributors to the orbit error budget have not changed since TOPEX/Poseidon static gravity tide models variable gravity solar radiation pressure station / data errors reference frame - PowerPoint PPT Presentation

Transcript of POD/Geoid Splinter Summary

Page 1: POD/Geoid Splinter Summary

POD/Geoid Splinter Summary

OSTS Meeting, Hobart 2007

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POD reportRevised orbit error budget

• Contributors to the orbit error budget have not changed since TOPEX/Poseidon– static gravity– tide models– variable gravity– solar radiation pressure– station / data errors– reference frame– geocenter motion– orbit determination noise

• but they are now lower and better characterized

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Static Gravity

• Differences between newer GRACE models are small• order 1 harmonics contribute largest GCEs

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Tide models

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Variable gravity

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Time-Varying Atmospheric Gravity• SLR residuals RMS globally reduced by ~1 mm when

adding atmospheric gravity

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Impact on GCEs

Mean Radial Difference relative to JPL06b in mm(averaged over cycles 22 to 99 = Aug 02 to Sep 04)

GDR-B SHDP AOD1B

• Atmospheric gravity reduces geographically correlated differences with JPL06b reduced dynamics orbits

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Grace-derived time-variable gravity to 20x20 (annual terms only)

• Monthly solutions from KBRR data only• Fit mean, trend, & annual harmonic• 2 solutions: 1-yr & 3-yr data span

Jason SLR/DORIS orbit summary (cycles 1-176)TVG model

average RMS residuals

DORIS(mm/s)

SLR(cm)

Crossovers(cm)

atmosphere gravity + (no annual) 0.3699 1.482 5.580atmosphere gravity + tvg1 (1-year annual) 0.3698 1.462 5.577atmosphere gravity + tvg3 (3-year annual) 0.3698 1.461 5.577

Reference: ‘Monthly spherical harmonics gravity field solutions determined from GRACE inter-satellite data alone,’ Luthcke et al., Geophyscal Research Letters, 2006.

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POD Results for JASON

54.7 mm54.6 mm54.6 mm54.3 mm

.3219 mm/s

.3185 mm/s

.3185 mm/s

.3181 mm/s

12.7 mm12.2 mm11.9 mm11.5 mm

RMS values of one arc per month of the obervations residuals after orbit adjustment

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Solar radiation pressure

• There is evidence of small residual errors in both the scaled box-wing (GDR-B) and the UCL (JPL) model

from L. Cerri

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Solar Radiation PressureSRP is largest surface force acting on T/P and Jason-1

(T/P area-to-mass ratio is half that of Jason-1)

It is easily shown that a bias in the SRP model interacts with estimated empirical 1/rev parameters to create periodic Z-shift correlated with beta-prime

Z variation due to 3% scale error in SRP model

from J. Ries

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Solar radiation pressure

Jason SRP model performancecycles 1-180

average RMS residuals

DORIS(mm/s)

SLR(cm)

Crossovers(cm)

nominal (CR =1.000) 0.3688 1.460 5.577

nominal (CR =0.914) 0.3688 1.433 5.585

UCL (untuned) 0.3632* 1.445* ----

* fewer points used (dynamic editing)

• GSFC’s attempt to rescale model at GSFC leads to mixed results

from F. Lemoine

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Solar radiation pressure

Jason SLR/DORIS nominal SRP - JPL GPS6b orbit differences

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

0 20 40 60 80 100 120 140

cycle

Mea

n Z

(cm

)

Cr=1.000

Cr=0.914

Z-shift induced by rescaling of SRP model not sufficient to explainZ offset between DORIS/SLR and GPS orbits

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Station / Data errors

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Jason DORIS SAA correction

Jason Doris residuals: SLR/DORIS ITRF2000 orbits

0.28

0.33

0.38

0.43

0.48

0 20 40 60 80 100 120 140 160 180

cycle

rms

resi

dual

s (m

m/s

)

GSFC

GSFC w SAA correction

GDR-A

Jason SLR/DORIS

ITRF2000 orbitscycles 1-177

average RMS residuals

DORIS(mm/s)

SLR (cm)

Crossover (cm)

GSFC 0.4078 1.482 5.585

GSFC w SAA corr. 0.3695 1.46

1 5.577

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Jason DORIS SAA correction: Comparison of SLR/DORIS & SLR/Crossover Orbits

Jason (SLR/DORIS - SLR/Crossover) mean radial orbit differences over water

slope = -0.20 mm/yr

slope = -0.08 mm/yr

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

3

3.5

0 20 40 60 80 100 120 140 160 180

cycle

Mea

n ra

dial

(mm

)

saa corrected cycles 1-90

saa corrected cycles 92-177

cycle 91

saa not-corrected cycles 1-90

saa not-corrected cycles 92-177

Linear (saa corrected cycles 1-90)

Linear (saa corrected cycles 92-177)Linear (saa not-corrected cycles 1-90)Linear (saa not-corrected cycles92-177)

~ 0.9 mm oscillator jump at cycle 91

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Jason DORIS SAA correction

Jason SLR/DORIS (SAA uncorrected-corrected) orbit differences and DORIS points

-2

-1.5

-1

-0.5

0

0.5

1

1.5

0 20 40 60 80 100 120 140 160 180

Jason cycle

cm

65000

75000

85000

95000

105000

115000

125000

num

ber D

OR

IS p

oint

s

radial rms

mean Z

cycle 91

doris points

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Reference frame

• ITRF2005– results indicate that ITRF2005 corrects a drift in the

centering of ITRF2000– Z drifts between the various orbits are significantly

reduced with ITRF2005– transition from ITRF2000 to ITRF2005 will induce a

shift in Z

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Evaluation of new Jason orbits based on ITRF2005

Jason OrbitsSLR/DORISCycles 1-177

DORIS RMS

(mm/s)

SLR RMS(cm)

SLR mean(cm)

AltimeterCrossoverRMS (cm)

ITRF2000 0.3740 1.440 -0.058 5.578

ITRF2005 0.3734 1.423 0.257 5.573

ITRF2005SLR-Rescaled w. scale-rate

0.3734 1.365 -0.030 5.576

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Evaluation of new TOPEX orbits based on ITRF2005

TOPEX SLR/DORIS Orbits

Cycles 1-364

DORIS RMS

(mm/s)

SLR RMS(cm)

SLR mean(cm)

AltimeterCrossoverRMS (cm)

GDR 0.5348 2.210 0.323 ---ITRF2000 0.5104 1.815 0.161 ---ITRF2005 0.5104 1.870 0.323 ---

ITRF2005 SLR-rescaled w. scale-rate

0.5102 1.771 0.195 ---

Subset Analysis:21 TOPEX Cycles (344-364)

ITRF2000 0.4678 1.629 0.001 5.493ITRF2005 0.4878 1.670 0.264 5.501

ITRF2005 SLR-rescaled

w. scale-rate

0.4676 1.572 0.099 5.494

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Annual signal amplitude(TVG annual – none)

Geographically correlated error (GGM02C-JGM3)

TOPEX Radial Orbit Difference Trends(ITRF2005 – GDR (CSR95))

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Jason (and TOPEX) radial orbit differences are driven by the difference in Z

Long-term Orbit Error and the Terrestrial Reference Frame (TRF)

Jason ITRF2005-ITRF2000 mean orbit differences (Jan '02 - Oct '06)

Z slope = +1.44 mm/yr

slope = -0.31 mm/year

-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

0.5

0 20 40 60 80 100 120 140 160 180 200

cycle

radi

al o

ver w

ater

(mm

)

0

2

4

6

8

10

12

14

16

18

Z (m

m)

radialZLinear (Z)Linear (radial)

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TOPEX Radial Orbit Difference TrendITRF2005 – GDR (CSR95)

Consequent error in estimated regional and global

MSL trends

TOPEX ITRF2005-GDR(CSR95) mean orbit differences (Jan '93 - Dec '01)

slope = -0.28 mm/yr

-5

-4

-3

-2

-1

0

1

2

3

4

5

0 50 100 150 200 250 300 350

cycle

radi

al (m

m)

radial (over water)

Linear (radial (over water))

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Jason GSFC TRF orbit trendsJason GSFC SLR/DORIS ITRF2005 - ITRF2000 orbit differences

slope = +1.44 mm/yr

slope = +1.27 mm/yr

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0 20 40 60 80 100 120 140 160 180 200

cycle

Mea

n Z

(cm

)

itrf2005-itrf2000

itrf2005s-itrf2000

Linear (itrf2005-itrf2000)

Linear (itrf2005s-itrf2000)

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Jason TRF orbit trends – JPL GPSJason ITRF2005 / ITRF2000 differences with ITRF2000 JPL GPS-only orbits

slope = +2.24 mm/yr

slope = +0.20 mm/yr

slope = +2.38 mm/yr

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

3

0 20 40 60 80 100 120 140 160

cycle

Mea

n Z

(cm

)

jpl_gps6b - slr/xover itrf2000slr/xover itrf2005 - jpl_gps6bslr/xover (itrf2005-itrf2000)Linear (jpl_gps6b - slr/xover itrf2000)Linear (slr/xover itrf2005 - jpl_gps6b)Linear (slr/xover (itrf2005-itrf2000))

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Geocenter motion