Launch pads for climate studies

THIS YEAR, US President George Bush announced that US $1.4 billion is to be made available in 1993 to the US Global Change Research Programme (USGCRP), which will lead to a massive increase in humankind's understanding of the earth's atomosphere. As a part of the programme, a network of remote sensing satellites and instruments, together called the Earth Observing System (EOS), is being deployed by the National Aeronautical and Space Adminis tration (NASA). Originally, to obtain all the essential observations needed, one large space platform capable of carrying all the necessary instruments was planned.

But the Department of Defence and the Department of Energy have since declassified several technologies and the US Air Force has also indicated that launch vehicles that were earlier only available to the military can be used. As a result, the US government has decided to replace the single platform EOS with a fleet of smaller platforms, which would manage to provide simultaneous observations of the atmosphere. The proposed EOS will consist of three medium-sized platforms. Each spacecraft will fly in a sun-synchronous orbit, but with different crossing times. The EOS spacecraft will provide data over a 15-year period, to provide longterm continuity of observations.

One spacecraft, scheduled to be launched in 1998, will collect data related to climate and hydrological systems, greenhouse gases and radiation balance. The second platform will colle& data on the impact of clouds on radiative balance and greenhouse gases. This is scheduled for launch in late 2000. The third platform will contain instruments required for measuring atmospheric composition and sea surface winds. Two more series of smaller spacecraft are also planned.

According to D Allen Bromley, assistant to the US President for science and technology, the enormous quantity of data generated by this system of satellites will equal every 4.8 days the amount' of-information contained it the entire US Library of Congress This massive data gathering and anal ysis exercise will ba-roordinated by NASA. But before that, the speed memory, capacity and data transfer rates will have to increase by 100 to 1,000 times in the next few years. It is an ambitious exercise. As Bromley points out, "Only with advances in space-based and ground-based activities, can we hope to answer the fundamental questions surrounding our global environment."

NASA's space-based programme includes the Mission to Planet Earth developed by the Goddard Space. September, the Upper Atmosphere Research Satellite was successfully launched aboard the space shuttle, Discovery. The satellite is studying the dynamics of the stratosphere and the mesosphere Observations on the chemical species responsible for dqstroying the ozone layer am already coming in. The satellite closely monitored the impact of the Mt Pinatubo vblcanic eruption in April 1991 which, it is now believed, can retard global warming but adversely affect the,ozone layer.