There is a need of a constellation of satellites with multisectoral sensors to predict,mitigate and manage disasters like cyclones,the Indian Space Research Organisation (ISRO) has said. No single satellite can hope to meet all these needs. Rather,what disaster managers need is a constellation of satellites carrying a range of sensors, Director,Space Application Centre,ISRO Ranganath Navalgund told from Ahmedabad on Thursday. The constellation plan is a part of the Umbrella Plan of the organisation,he said. Disasters come in all shapes and sizes,needing varying data during the disaster cycle of mitigation,preparedness,response and recovery,Navalgund said. Many studies suggest at least eight satellites with dual capability sensors can collect both high and low spatial resolution data and an equal split between optical (including thermal) and microwave instruments. The satellites should also be agile,they should allow rapid changes in camera orientation so that a disaster area can be kept in view longer, he said. However,India currently makes use of data from different satellites that are already operating for disaster management. Even yesterdays cyclone Phyan in Arabian sea was tracked by INSAT-3A Kalpana and recently launched Oceansat-2 with KU band and scatterometer,he said. Even yesterdays cyclone Phyan in Arabian sea was tracked by INSAT-3A Kalpana and recently launched Oceansat-2 with KU band and scatterometer,he said. Crucially,different situations need data collected in different wavebands - like optical and near infrared data can map land use or assess agricultural droughts. But to track a cyclones eye,or monitor flooded areas beneath cloud,microwave sensors are needed, Navalgund said. Landslide studies depend on accurate high-resolution digital elevation models,which require data collected by stereo-viewing optical sensors like Cartosat¿1,Interferometric Synthetic Aperture Radars (InSARs) or Light Detection and Ranging (LIDAR) instruments. Disaster managers really need satellites incorporating sensors that collect data in all these regions of the electromagnetic spectrum,he said. There is often an awkward trade-off between temporal and spatial resolutions. Managing many natural disasters,such as cyclones or fires,demands detailed and continuous data. But although geostationary satellites,such as Meteosat or INSAT (Indian National Satellite System)/ Kalpana,provide almost constant surveillance (every 15 minutes),they lack detail (their spatial resolution is low), Navalgund said. Conversely,polar-orbiting satellites offer higher spatial resolution data (even down to less than 1m) but information is only collected once every few days. In flood monitoring,this can pose a real problem. Low spatial resolution data can map out large inundated areas,but relief efforts really need more detailed,yet still timely data on infrastructure,like submerged bridges,drains and roads, SAC director said. A constellation of polar-orbiting satellites,equally spaced around a sun-synchronous orbit to provide continuous coverage over any given place,could solve this,he said. Such a constellation,designed primarily for disaster management,could offer more frequent data in the right part of the spectrum and India is planning on these lines. Geostationary satellites,predominantly designed for weather forecasting,are good at spotting a cyclones forming,tracking its movements,and predicting land fall points. But they dont usually carry microwave sensors,which are needed to estimate a cyclones intensity ¿ critical for predicting potential damage. Navalgund said,one such Disaster Monitoring Constellation (DMC) has been designed by Surrey Satellite Technology,UK with seven equally-spaced satellites. He pointed out that the most important thing for effective disaster monitoring and mitigation is that satellite data reaches managers and emergency planners in an easy-to-use format. So satellites in a constellation must provide a certain amount of on-board processing and automatic analysis communications satellites.
