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

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

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  1. 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

  2. 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.

  3. Absolute RangeCalibration • Regional calibration for maximum precision • Co-ordinated campaign using: • Buoys • Tide Gauges • Modelling • Permanent sites for long term monitoring

  4. 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

  5. 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:

  6. 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

  7. 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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