One of the main Lunokhod’s systems was temperature control system that maintained the necessary temperature in the hermetic body at the outboard temperature from –150°С at night to + 150°С in day time. The temperature control was very reliable and the equipment in the vehicle was safe.
Apart from test models of Lunokhod, it had four functioning models. The first one was Lunokhod-0, but it didn’t reach the space due to the rocket crash during the start. Lunokhod-1 overcame 10 540 meters on the Moon and performed many scientific tasks. The warranty period for the vehicle was three months but it worked for almost a year – from November 17, 1970 to September 15, 1971. It was put out of service due to the failure of the isotope heat source (everything inside the eight-wheeled robot got frozen on a cold lunar night at -150°С).
Lunokhod-2 travelled 40,000 meters on the Moon and was put out of operation not because of its condition but following the meeting with an insidious crater (the heat exchanging cover was contaminated with soil).
Lunokhod-3 was not even given a chance to perform its task, the Soviet lunar program was suspended. Today it is kept in a safe place.