The Soviet Union placed a series of nuclear-powered, radar-equipped ocean reconnaissance satellites, known as RORSATs in the west, into Earth orbit beginning in 1967. Employing powerful radars and working in pairs, these spacecraft kept an eye on U.S. ships for Soviet naval forces. Image
Russia's Space Forces minimized the risk posed by a long-retired nuclear-powered satellite that the U.S. Space Surveillance Network (SSN) identified as producing "an unexpected debris cloud" in July.
In statements released Jan. 21, the Space Forces said the Cosmos 1818 satellite, orbiting at 800 kilometers, is not a danger to other satellites in that orbit and will disintegrate when it reenters the Earth's atmosphere sometime in the middle of this century.
A NASA analysis of SSN data found that Cosmos 1818, launched in February 1987, was the source of a "fragmentation event" around July 4 that released at least 30 small pieces of debris.
In its Orbital Debris Quarterly News report issued Jan. 15, NASA's Orbital Debris Program Office says the debris could be droplets of sodium-potassium, which was used as a coolant for the satellite's nuclear power generator. Direct exposure to the sun could have warmed the coolant to a liquid state. NASA said the released objects resemble metallic spheres.
A satellite featuring a similar design, called Cosmos 1867, has not released any similar debris up to now, NASA said.
The NASA analysis said Cosmos 1818 and 1867 were test satellites to demonstrate a new kind of nuclear power in low Earth orbit, but at an altitude much higher than the 250-kilometer operating orbit of Russia's Rorsat ocean-reconnaissance satellites. A Rorsat satellite failed in orbit in 1978, breaking up in the atmosphere and causing radioactive debris to fall over Canada.
The NASA report said that two years after China used a ground-based missile to destroy the retired Chinese Fengyun-1C weather satellite in an 800-kilometer orbit, SSN is tracking nearly 2,800 pieces of debris measuring at least 5 centimeters in diameter. "The estimated population of debris larger than 1 centimeter is greater than 150,000," NASA said. "The Fengyun-1C debris cloud easily constitutes the largest collection of fragments in Earth orbit."
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