Tuesday, November 17, 2009

Constellation Of Satellites Needed For Disaster Management: ISRO

The Indian Space Research Organisation (ISRO) has stressed on the need to have a constellation of satellites with multispectral sensors to predict, mitigate and manage disasters.

"Exactly how many satellites an effective constellation would need is still open for debate. 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 PTI from Ahmedabad.

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 which are already operating for disaster management. Even yesterday's 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 cyclone's 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.

Even yesterday's 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 cyclone's 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.

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