In a scientific first yesterday, Russia launched twin German-U.S. satellites into orbit. The satellites, which will fly in tandem at a distance of 200 kilometers from each other, are designed to measure the Earth's gravitational field with unprecedented accuracy. Scientists hope this will yield new information on the effects of climate change, perhaps answering the riddle of whether global warming is happening -- or not.
Prague, 18 March 2002 (RFE/RL) -- The program is called GRACE, which stands for Gravity Recovery and Climate Experiment.
Two scientific satellites launched yesterday in Russia, jointly operated by the U.S. and German space programs, will circle the Earth in tandem for the next five years measuring changes to the Earth's gravity field over both land and sea. What makes the GRACE program unique is that the data obtained, scientists hope, will be far more accurate than any measurements known to date, helping to advance our ability to make long-range climate forecasts.
Volker Liebig is a program director at Germany's DLR Space Center. He spoke to RFE/RL about the mission.
"The objective of the GRACE mission is to measure the gravity field of the Earth to an accuracy which has never been achieved -- in fact about 1,000 times better than we have know it so far," Liebig said. "The gravity field of Earth is a very important basic data set which we need, for example, to detect ocean currents in the sea. It is important for climate models but also for ship routing."
Scientists hope that by tracking how the Earth's water currents travel, which will be done by measuring changes to gravitational pull over the oceans, they will come to better understand how our climate is changing. Ocean currents transport large amounts of heat between continents, and since two-thirds of our planet is water, the influence of the oceans in shaping climate change is of primary importance.
How will the experiment work? According to the American space agency NASA, as the GRACE satellites circle the globe 16 times a day -- some 200 kilometers apart -- they will be able to detect minute variations in the Earth's surface mass below and corresponding variations in the Earth's gravitational pull, even over bodies of water.
Regions of stronger gravity will affect the lead satellite first, pulling it away from the second satellite. By measuring the constantly changing distance between the two satellites and combining those readings with other measurements, scientists hope to be able to construct a precise gravity map. The satellites' detection system is so sophisticated it will be able to detect separation changes as small as 10 microns -- or one-tenth the width of a human hair -- over a distance of some 200 kilometers.
Although the scientific part of the project is a U.S.-German venture, the satellite launch took place at the Plesetsk space complex in northern Russia, the first of a NASA spacecraft from a site abroad. The mission used a converted ballistic missile as the launch vehicle -- a textbook demonstration of international cooperation and swords-to-ploughshares technology.
Liebig explained: "Russia was chosen because we have a joint venture between a German company -- Astrium -- and a Russian company -- Krunichev -- marketing former ballistic missiles of the Soviet Union, the former SS-19, under the name ROKOT. And the company, the joint venture, is named EUROKOT. It has very attractive prices to offer, especially for scientific satellites, where you have to save money. So this was the most competitive offer we could get."
By the time the GRACE satellites have spun around the globe 29,000 times -- in about five years -- we may be closer to resolving the question of whether global warming is actually taking place and if it is, which global regions may be affected most.