Radiometric and geometric scarab-megha-tropiques ground calibration comparison with first in orbit calibration

The Scarab-3 instrument, part of the Indian-French Megha-Tropiques mission [1], has been launched in october 2011. It is a radiometer dedicated to earth radiation budget. CNES is prime of the development of this instrument. Last year, CNES conducted the final integration of the instrument and the radiometric/geometric calibrations. Two main spectral bands are measured by this instrument: A shortwave (SW) channel dedicated to solar fluxes and a Total (T) channel for (total) fluxes combining the infra-red earth radiance and the albedo. The earth long wave (LW) radiance is computed by subtracting the SW channel to the Total channel. Thus is defined a 3rd (virtual) LW channel. To obtain a good radiometric accuracy, intensive tests have been conducted using integrating sphere, black body calibration, vacuum tests and collimator test. After a brief sum up of the instrument, the results of the calibration will be presented and compared with the first in orbit calibration.