ScaRaB: first results of the scanner for radiative budget on board the Indo-French satellite Megha-Tropiques

ScaRaB (SCAnner for RAdiation Budget) is the name of three radiometers whose two first flight models have been launched in 1994 and 1997. The instruments were mounted on-board Russian satellites, METEOR and RESURS. On October 12th, a last model has been launched from the Indian site of Sriharikota. ScaRaB is a passenger of MEGHATROPIQUES, an Indo-French joint Satellite Mission for studying the water cycle and energy exchanges in the tropics. The orbit is circular inclined 20deg. ScaRaB is compatible with CERES mission. Two main spectral bands are measured by the radiometer: A short-wave (SW) channel (0.2 – 4 μm) dedicated to solar fluxes and a Total (Tot) channel (0.2 – 200 μm) for (total) fluxes combining the infrared earth radiance and the albedo. The earth long-wave (LW) radiance is isolated by subtracting the SW channel to the Total channel. Thus is defined a supplemental (virtual) channel.