"Satellite plays important role in detection and monitoring of flood situations over large regions. Optical remote sensing from geostationary platform (Insat-3D/3DR) provides rapid and valuable information on cloud patterns and meteorological parameters (rainfall); however, unable to image the surface water conditions in presence of cloud," says Isro.
Microwave remote sensing techniques have a unique advantage in which electromagnetic radiation penetrate the clouds and senses the surface hydrological characteristics. The data from ScatSat-1 (launched by PSLV-C35 on September 26, 2016) was used for the detection of the flood situations over India. ScatSat-1 is a continuity mission for Oceansat-2 Scatterometer for Ocean weather forecasting, cyclone detection, and tracking.
ScatSat-1 observations in Ku-band for backscattering and brightness temperatures have been analyzed for flood detection and monitoring over India with special emphasis in Gujarat and southern parts of Rajasthan in the past. Merging of backscattering and brightness temperature data helped to delineate the regions, which were flooded, partially submerged or existed in different soil wetness conditions (saturated or dry).
Analysis showed the usefulness of ScatSat-1 mission in detecting and monitoring extreme events such as flood with high temporal resolution (daily).
"When we have good number of satellites, we know the situation yesterday and today. We will be able to assess the situation and come to an understanding about what to expect next. These periodical updates are helpful in situations like flood in Himalaya when we can forewarn the State governments about a likely flood once the water reaches down to the locations where people reside," said M Annadurai, who was the director of U R Rao Satellite Centre, Isro, till July 31, 2018. Oceansat-2, Insat 3DR, Cartosat 2 and 2A and Resourcesat-2 are some of the satellites that are helping the country to know about the changes happening in Earth and its atmosphere, periodically, over India and its neighbourhood.
While the remote sensing satellites could be supportive to predict the weather with the wind flow and speed, moisture, clouds and other parameters, the radar satellites help to see beyond the clouds, to the actual ground situation, giving a larger picture from hundreds of kilometers above the land. Oceansat, Resourcesat, and Cartosat are used to take pictures at a closer range, at a lower altitude. This is helpful in identifying forest fire and other natural calamities as they take better pictures than the satellites from the distance. The data sent from the remote terminals also help the scientists to come to a conclusion on the ground situation.
However, the challenge for the satellites closer to the Earth is that they require more power to operate and they are heavier considering they need to carry larger solar panels to meet the power requirement. This makes the life of these satellites shorter compared to those which are placed at orbits almost 800 kilometers away from the Earth. Isro has been working on technology to make these satellites less power consuming and thus smaller, so that these all weather satellites can live longer and serve the needs of the country.