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SNAP-10A was launched from Vandenberg Air Force Base by an ATLAS Agena D rocket on April 3, 1965 into a low Earth orbit altitude of approx. 1,300 km. It is in a slightly retrograde polar orbit — this ensured that the spent rocket stages landed in the ocean. Its nuclear electrical source, made up of thermoelectric elements, was intended to produce over 500 watts of electrical power for one year. After 43 days, an onboard voltage regulator within the spacecraft – unrelated to the SNAP reactor – failed, causing the reactor core to be shut down, after reaching a maximum output of 590 watts.
After the 1965 system failure, the reactor was left in a 1,300-kilometre (700 nmi) Earth orbit for an expected duration of 4,000 years.
In November 1979 the vehicle began shedding, eventually losing 50 pieces of traceable debris. The reasons were unknown, but the cause could have been a collision. Although the main body remains in place, radioactive material may have been released.
As of 2010, more than 30 small fission power system nuclear reactors have been sent into space in Soviet RORSAT satellites; also, over 40 radioisotope thermoelectric generators have been used globally (principally US and USSR) on space missions.