Two geostationary satellites ;, Kalpana-1 (74o E) and INSAT-3A (93.5oE), are in orbit. Kalpana -1 and INSAT-3A has VHRR sensor. INSAT-3A in addition carries a CCD camera with a resolution of 1kmx1km. The meteorological products are being routinely generated from these satellites. The data from METEOSAT-7 over Indian Ocean region is very useful for validation and inter calibration of the products. The utilization of these products in numerical modeling and the regular weather forecasting has significant role.
INSAT-3D to be launched this year will have six channel imager and nineteen channel sounder for retrieving temperature and humidity profiles over high humidity regions. Suitable algorithms for the retrieval are under investigation. The experience gained with sounder onboard GOES would be helpful in developing retrieval algorithm. The validation of the retrieved products from imager along with METEOSAT, GMS etc is desirable. The accurate parameter retrieval either from imager or from sounder essentially depends upon the extent of radiometric and geometric correction applied, calibration, normalization, navigation and earth location of basic pixel data. INSAT-3D is well equipped for these. Follow up of INSAT-3D are being examined. The possibility of the hyper-spectral sounder is being particularly studied.
In the time frame of INSAT-3D three additional Indian polar orbiting satellites will be available : Oceansat-II (follow up of Oceansat-1), Megha-Tropiques and SARAL. OCEANSAT-2 satellite will be carrying a Ku-band scatterometer similar to Quikscat and an Ocean Colour Monitor (OCM).. The retrieval algorithms for OCEANSAT-II are at advance stages of development. The Megha-Tropiques (MT) satellite (a joint Indo-French mission) is designed to study how the water cycle affects atmospheric climate processes over the tropics. It will carry three payloads namely; MADRAS, a microwave imager operating in the frequency range from 19 to 85 GHz for measuring rain, atmospheric water vapour content, liquid water content and ocean surface wind speed; SAPHIR, a multi-channel microwave sounder operating at 183 GHz to measure vertical profiles of atmospheric humidity over land and ocean and; ScaRab, operating in optical region for estimating earth radiation budget over tropical convective region. Both Oceansat-II and Megha-Tropiques will additionally be equipped for GPS based radio-occultation measurements. SARAL , a polar orbiting satellite will carry a Ka band altimeter. The satellite is slated for launch in 2009.Other Indian Earth Observing Satellites for resources (called the IRS-series) operationally provides many land surface parameters useful for weather/climate modeling.
Thus number of Indian missions are co-existing for meteorological applications. All the above missions have strong operational and R & D application components. A few examples of these applications will also be discussed.
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