C. Technical Outline
The originality of the MEGHA-TROPIQUES mission resides in its orbit and sampling, and in its instrumental association. Therefore, this mission does not intend to use new techniques or concepts, but only proven concepts, eventually already developed instruments. These instruments may come from other programs, or may be designed to fly on other missions.
Although it is necessary to develop new instruments for this mission, they are all based on well-proven technologies. The detailed studies of the three instruments have now been performed, and we enter the phase of building the instruments :
MADRAS: the instrument is of the same type as SSM/I or TMI, the TRMM radiometer. From the radiometric point of view, it benefits in Europe from studies already performed for MHS (on METOP) or other microwave instruments. However, MADRAS is the first conical scanning radiometer ever built in Europe and India. This instrumental development has potential applications in other projects.
SAPHIR: the radiometric technology is well mastered. The antenna diameter is small and the scanning mechanism is simple. This will be a lightweight instrument. It could also be used on other missions, for example on microsatellites.
ScaRaB : The same sensor module that has been proven efficient and stable in the previous ScaRaB flights will be used. Changes will be done in the structure and the electronics in order to take into account technical advances done since the launch of the first ScaRaB.
a small satellite with a qualified platform:
This mission has been studied first in the frame of the small satellite program of CNES. Specific constraints on the weight of the payload, the available power, the data flow rate are induced. In this context, the small platform PROTEUS was taken as the reference bus for the accommodation of the instruments. Further sharing arrangements led to the choice of an Indian IRS platform, which gives more margins in terms of mass of the payload and available power.
There are few opportunities of launching satellites of this size in low near equatorial orbit. The use of an Indian PSLV rocket has been chosen since the beginning of the French-Indian cooperation.