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RA-2/MWR/DORIS Session Instrument, Level 1b and Absolute Calibrations by M. Roca et al. Instrument and Level 1b overview Absolute Range Calibration: preliminary results and next steps Absolute Sigma-0 Calibration: results and future plans. Instrument and Level 1b Overview. Instrument: - PowerPoint PPT Presentation
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Page 1ENVISAT Validation Review - ESRIN - 9–13 Dec 2002 - RA2/MWR/DORIS
RA-2/MWR/DORIS Session
Instrument, Level 1b and Absolute Calibrations
by M. Roca et al.
Instrument and Level 1b overview
Absolute Range Calibration: preliminary results and next steps
Absolute Sigma-0 Calibration: results and future plans
Page 2ENVISAT Validation Review - ESRIN - 9–13 Dec 2002 - RA2/MWR/DORIS
Instrument and Level 1b OverviewInstrument:* All parameter optimised by the Calibration review (last
modification in September)* Instrument Performance have since been excellent !Level 1b:* Correction for datation and range bias was verified.
Implementation in the IPF since v4.53.* Further correction in the sigma-0 computation
implemented in the reference processor. To be in the next version of the IPF.
* Modification of the PTR computation also included in the reference processor. To be in the next version of the IPF.
Page 3ENVISAT Validation Review - ESRIN - 9–13 Dec 2002 - RA2/MWR/DORIS
* Regional calibration for maximum precision
* Co-ordinated campaign using:• Buoys• Tide Gauges• Modelling
* Permanent sites for long term monitoring
Absolute Range Calibration
Page 4ENVISAT Validation Review - ESRIN - 9–13 Dec 2002 - RA2/MWR/DORIS
Absolute Range Calibration - Preliminary Results
* A total of in-situ measurements:• 44 measurements of light GPS buoys (IEEC/ICM)• 2 moored GPS buoys (IfGN), with a total of 16 passes each• 6 coastal tide gauges (IMEDEA, ICM, LEGOS, SHOM…)
* Propagation of in-situ measurements towards the satellite tracks through geophysical models.
* Dedicated corrections to be applied to the altimeter estimated range (from Level 2 products) provided by several groups:• short arc orbits, by DEOS• atmospheric correction (with ECMWF and on-ground MWR),
by TOS
Page 5ENVISAT Validation Review - ESRIN - 9–13 Dec 2002 - RA2/MWR/DORIS
Absolute Range Calibration - Preliminary Results
• include coastal tide gauges in the bias estimation once errors in the MSS model at the coast have been reduced;
• improved ionospheric correction;• new model for sea state bias developed by CLS to be applied;• formal computation of the error;• error to be reduced to 1 cm, as per requirement.
Long term monitoring with Casablanca oil platform and Eivissa TG.
-1
-0.5
0
0.5
1
1.5
19160 19180 19200 19220 19240 19260 19280 19300
CasablancaFTB2FTB4ICM
bias estimation = 41 cm ?quoted error = 6 cm ?
Objectives for EGU, April’2003:
Page 6ENVISAT Validation Review - ESRIN - 9–13 Dec 2002 - RA2/MWR/DORIS
Sigma-0 Absolute Calibration* Absolute Sigma-0
calibration never been attempted
* Scientific needs demonstrated
* Requirement: ±0.5 dB ±0.1 dB stability over
3 years
* Dedicated transponder developed at ESTEC
Page 7ENVISAT Validation Review - ESRIN - 9–13 Dec 2002 - RA2/MWR/DORIS
Sigma-0 - Absolute Calibration Results* Transponder calibrated
– RCS = 75.08 dB m^2;– rss = 0.11 dB; and – stability = 0.06 dB.
RA-2 power bias = + 0.831 dBEstimated error = 0.28 dB
* Further improvement is expected with the analysis bias with the we need to retrieve more passes.
* Future: a site will be identified in the vicinity of ESRIN, where the TRP will be located for further measurement, and eventually, drift monitoring.
Measured Received Power vs Theoretical Power
y = -0.0027x2 + 0.1643x + 21.953
y = -0.0025x2 + 0.1443x + 23.3
21
22
23
24
25
26
27
1 6 11 16 21 26 31 36 41 46 51 56 61 66data_blocks
power [dB]
Theor_power Eval_area_pw Poly. (Theor_power) Poly. (Eval_area_pw)