Instrument and Level 1b Overview:
Instrument and Level 1b Overview Instrument:
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.
Slide3:
Regional calibration for maximum precision
Co-ordinated campaign using:
Buoys
Tide Gauges
Modelling
Permanent sites for long term monitoring Absolute Range Calibration
Absolute Range Calibration - Preliminary Results:
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
Absolute Range Calibration - Preliminary Results:
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. bias estimation = 41 cm ?
quoted error = 6 cm ? Objectives for EGU, April’2003:
Sigma-0 Absolute Calibration:
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
Sigma-0 - Absolute Calibration Results:
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 dB
Estimated 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.