Communications Satellites

On February 10, the Iridium 33 and Cosmos 2251 communications satellites collided over northern Siberia, at approximately 1656 GMT.The impact between the Iridium Satellite LLC-owned satellite and the 16-year-old defunct Russian military satellite occurred at a closing speed of well over 15,000 mph, 490 miles above the face of the Earth. The collision occurred at roughly 780 kilometers (485 miles), a low-earth orbit (LEO) altitude used by satellites that monitor weather and carry telephone communications. It is considered the most crowded area of space.GPS and GNSS satellites are in medium-earth orbits, below the 22,300 miles of geostationary satellites and above LEO satellites.Bethesda, Maryland-based Iridium Satellite LLC has stated that the collision is not the result of a failure on the part of the 560-kg Iridium satellite or its technology, saying that it appears the satellite collided with a non-operational 900-kg Russian satellite. Iridium Satellite LLC operates a constellation of 66 LEO satellites that provide voice and data services for areas not served by ground-based communication networks. The Iridium 33 was launched in 1997.However, an official of the Russian Defense Ministry has implied that the Iridium satellite should have known it would crash into "junk" at that altitude.As for the United States' position, "We did not predict this collision," said Pentagon spokesman Bryan Whitman on Thursday.The U.S. Joint Space Operations Center was tracking 500 to 600 new bits of debris, some as small as 10 centimeters (3.9 inches) across, in addition to the 18,000 or so other man-made objects it has catalogued in space. It tracks so many that it has to decide which to follow most closely, such as the International Space Station (ISS) or manned space flights. The ISS flies at an even lower altitude than where the collision occurred."There are limits on your ability to track and compute every piece of orbiting man made object," Whitman said. "It's an unfortunate incident that highlights the importance of cooperation and collaboration in space.”Satellites that are "going dead" can be put in a place in space where there is no activity, or maneuvered into a safe descent back to Earth, he said.But Whitman refrained from accusing the Russians of negligence, saying that some of the procedures for handling dying satellites were introduced long after the satellite's launch in 1993.He said he had been told that Tuesday's collision was not the first of its kind, adding that "there have been three to four other events."NASA spokesman John Yembrick said there have been "three other cases in which space objects orbiting at hypervelocity have collided accidentally." But he added that "these were all minor events involving spent rockets or small satellites with only a few pieces of resulting debris."To support the space community in better understanding this unprecedented satellite-to-satellite collision, Analytical Graphics, Inc. and CSSI have used their software to reconstruct the event. The software is also being used to help assess the possibility of additional collisions by applying breakup models for debris prediction. Available tools include videos, interactive 3D Viewer files, and high-resolution images.

Geodetic / Global Positioning Systems

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Communications Satellites

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