Image courtesy of ISRO
Thales Alenia Space has delivered to the Indian Space Research Organization (ISRO) the flight model of the Radio Occultation Sounder for the Atmosphere (ROSA), which will be integrated into the Indian-French Megha-Tropiques mission that is designed to study our planet’s atmosphere. The delivery took place at ISRO’s Satellite Centre (ISAC) in Bangalore. Developed and built under ASI contract, the ROSA instrument is composed of a GPS receiver and two dual frequency antennas to pick up signals through the atmosphere. The instrument conducts its atmospheric sounding by monitoring navigation signals from the satellites of the GPS constellation while – as seen from the observing satellite – they set through the atmospheric limb on the Earth’s horizon or raise from it.
Raw data measured by ROSA are beamed back to Earth where the analysis of the phase delay on GPS signals crossing through the troposphere give a wealth of information, from which it is possible to determine the temperature, pressure and humidity of the atmosphere, and thus to issue forecasts on the evolution and motion of weather fronts, to evaluate climatic trends, and to map the electron density as well as irregularities in the ionosphere in order to predict magnetic storms. The radio-occultation method allows to achieve a better vertical resolution than other infrared or microwave sensors. The ROSA instrument was entirely designed and built by Thales Alenia Space Italy as prime contractor on behalf of ISRO. The instrument to be integrated on Megha-Tropiques will complement a science payload also consisting in three other instruments, one of which was jointly developed by ISRO and CNES (Centre National d’Etudes Spatiales), the French Space Agency, and the other two by CNES alone. This is the third similar sounder to be delivered by Thales Alenia Space. The previous two flight models were launched on September 23, 2009, onboard India’s Oceansat 2 satellite for ISRO, and on June 10, 2011, on Argentina’s SAC-D (Satelite de Aplicaciones Cientificas) for CONAE (Comisión Nacional de Actividades Espaciales).
Megha-Tropiques is scheduled to reach orbit on September 25 aboard an Indian PSLV launch vehicle, from the Satish Dawan Space Centre in Sriharikota Island, Andhra Pradesh.