redOrbit Staff & Wire Reports – Your Universe Online
Beware of falling satellites this weekend, as a European Space Agency (ESA) probe that had been mapping the planet’s gravitational field is expected to plummet back to Earth within the next few days.
The Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) satellite was launched in 2009, and managed to remain in low-orbit some 160 miles above the Earth thanks to its ion engine, UPI reported on Wednesday.
However, according to Nature World News, the GOCE completed its primary mission and ran out of fuel last month. Thus far, experts have been unable to predict exactly where the satellite will fall, but when it does, scientists expect as many as 45 pieces of debris, some weighing up to 200 pounds, could reach the surface.
“It’s rather hard to predict where the spacecraft will re-enter and impact. Concretely our best engineering prediction is now for a re-entry on Sunday, with a possibility for it slipping into early Monday,” GOCE mission manager Dr. Rune Floberghagen told Kenneth Chang of the New York Times.
Dr. Floberghagen explained that scientists will be able to provide a more definite time frame during which the fall will occur as it becomes closer, but since GOCE travels along a pole-to-pole orbit, it could theoretically land just about anywhere. He noted that between 15 and 20 square yards of the planet’s surface could be in danger.
“An uncontrolled re-entry was always the planned fate for GOCE,” Chang said. “Unlike most spacecraft, which use thrusters to adjust their orbits, it has a highly efficient propulsion system called an ion engine. Unlike thrusters, the engine can fire continuously to offset atmospheric drag.”
“This isn’t the first satellite to fall on earth,” Nature World News added. “In 2011, media was abuzz with stories of NASA’s Upper Atmosphere Research Satellite descent on the planet. In the same year, Russia’s Mars mission went awry and crashed into the Pacific… Scientists usually direct redundant satellites to a graveyard orbit, which is just above the GEO orbit. Other satellites are dropped back to earth using specialized equipment.”
The satellite’s instruments remain operational, Dr. Floberghagen said, and as the time nears they will be able to provide ESA scientists with more detailed data pertaining to GOCE’s final decent. Using the satellite’s data, scientists have been able to make global maps of ocean currents, and the information will also help them study ice sheets and convection occurring in the planet’s mantle, Chang added.
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