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Radioactive payload and debris

Radioactive payloads have been a concern for the community ever since radioactive debris decayed on Earth and contaminated entire regions. The first such event was in Jan 1978 when Cosmos 0954 decayed. Since then radioactive debris are closely monitored.

Those nuclear reactors which are to remain in orbit for a hundred years or so also caused problems to scientists. "Nuclear noise" as it is called cause gamma ray disturbances to astronomers. Indeed those reactors interfere periodically with gamma-ray surveys.

Russian satellites

The Russian Rorsat program is the most important program with nuclear reactor equipped satellites (32 spacecrafts). This engine (named Topol or Topaz) contains 50 kg of uranium and provides about 2000 W.

Two other Russian satellites are known to have a Topaz 1 reactor (also named Buk): Cosmos 1818 (87011A) and Cosmos 1867 (87060A), probably for test missions. This reactor provides around 5-6 kW power. It weighs 1350 kg.

A third engine named Enissei or Topaz 2 was built but has never been launched. It provides 6 kW and weighs 1 ton.

US satellites

The United States also used nuclear power on space missions. Two types of engines were used:

- Nuclear reactors which produce energy by nuclear fission (space based reactors use Uranium-235).
- RTGs (Radioisotope Thermoelectric Generator) which use the energy of radioactive decay (current SNAPs use Plutonium-238).

The SNAP (Systems for Nuclear Auxiliary Power) series include:

RTG engines Nuclear reactors Uncertain
Transit 4A OPS 4682 also called SNAPSHOT (65027A) LES 5
Transit 4B   LES 6
Nimbus 3   OPS 0757 also called Tacsat (69013A)
LES 8    
LES 9    

Other missions required nuclear power such as the Apollo moon missions experiments, the Viking Mars Landers, Pioneer and Voyager missions and the Galileo probe:

LAUNR Spacecraft Orbit
69-099 APOLLO 12 Moon
71-008 APOLLO 14 Moon
71-063 APOLLO 15 Moon
72-012A PIONEER 10 escaped solar system
72-031 APOLLO 16 Moon
72-096 APOLLO 17 Moon
73-019A PIONEER 11 escaped solar system
75-075 VIKING 1 LANDER Mars
75-083 VIKING 2 LANDER Mars
77-076A VOYAGER 2 escaped solar system
77-084A VOYAGER 1 escaped solar system
89-084B GALILEO Jupiter
90-090B ULYSSES Sun
97-061A CASSINI to Saturn

Pathfinder had RHUs (Radioisotope Heater Units) on the Sojourner rover.

Finally 3 missions failed:
Transit 5BN3 on 21 Apr 1964 aboard Thor Ablestar
Nimbus 3A
Apollo 13 (70029A) on 11 Apr 1970 which decayed on 17 Apr 1970

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