Satellite constellation suggested for collecting weather data

Updated on: Friday, January 06, 2012

For collecting accurate atmospheric data using GPS signals which could lead to better weather forecasts Scientists have mooted a proposal to have a constellation of six micro-satellites placed in a low-earth orbit.
The proposal was made by a former ISRO official D N Rao to Shailesh Nayak, Secretary Ministry of Earth Sciences at the 99th Indian Science Congress here.

Based on the COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) system implemented successfully by US and Taiwan, Rao said that six satellites, each weighing 50 kg, could collect data on vertical profile on temperature, pressure and humidity using the signals emitted by GPS satellites.

"Each micro-satellite will make 30 observations every day leading to nearly 200 observations every day from the the proposed constellation," Rao, Director (Research) at the SRM University in Chennai told.

Rao, a former Director of ISRO's National Atmospheric Research Laboratory, said the satellites, which would be equipped with a dual frequency GPS receiver, would measure the key parameters of the atmosphere using a technique called as radio occultation(GPS-RO).

The technique, first used to study atmospheres of other planets, measures the angle at which a radio signal emitted by a GPS satellite bends as it passes through the atmosphere just above the horizon.

"The GPS-RO gives very precise inputs about atmospheric data than the current radiosonde method. It is an emerging area," Nayak told.

A radiosonde is a small box-like instrument that is carried into the upper atmosphere by balloon. As it travels upward, it measures temperature with a thermometer, humidity with a hygrometer, and air pressure with a barometer and transmits the data to ground stations.

India has 35 stations that send radiosonde probes twice a day but their scope is limited as gives atmospheric measurements only over land surrounding the stations.

Moreover, radiosonde is a one shot measurement, Rao said.

The COSMIC system records over 2500 observations every day, but the it does not provide enough data about the tropics, the area of interest for India.

"The proposed constellation can fulfil the requirement," Rao said.

According to Rao, the total cost of launching and operating a constellation of six micro-satellites may not cost more than Rs 50 crore.

"I will request the Ministry of Earth Sciences and ISRO to consider the proposal to launch a constellation of six micro-satellites for atmospheric measurements using GPS-RO method," Rao said.

Satellite constellation suggested for collecting weather data

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