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RA-2/MWR/DORIS Session Instrument, Level 1b and Absolute Calibrations by M. Roca et al.

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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:

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slide1
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 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
Absolute RangeCalibration
  • Regional calibration for maximum precision
  • Co-ordinated campaign using:
    • Buoys
    • Tide Gauges
    • Modelling
  • Permanent sites for long term monitoring
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 results1
Absolute Range Calibration - Preliminary Results

bias estimation = 41 cm ?

quoted error = 6 cm ?

  • 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.

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.
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