Luna-21 space probe with Lunokhod-2 rover performed a soft landing on the surface of the Moon 45 years ago. Russian Space Systems Holding has published a declassified report about the work of the space station and problems that arose during the mission.
The remote control system of the Lunokhod lunar rover remain in use from January 16 till May 10, 1973. The communication devices that were used during the mission remained functional even after their mission life. The unique experience obtained during the mission was subsequently used to design other spacecraft to study planets of the solar system.
The declassified report consists of two parts. The first one describes the operation of the complex of on-board equipment with a system of low-frame television. The second part is medicated to the operation of the ground-based communication complex "Saturn-MS." The equipment was responsible for the control of the Lunokhod-2 lunar rover allowing to obtain images from the surface of the Earth's satellite.
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The equipment was tested profoundly in the autumn of 1972. First serious issues with the work of the remote control equipment appeared only during the 250th communication session, when engineers had to transmit the "stop" command to the Lunokhod three times as the rover was traveling to a crater.
The report gives the comparative data of the low-frame television system - the "eyes" of the drivers of USSR's Lunokhod-1 and Lunokhod-2 lunar rovers. The modernised system allowed the second device to move much faster. The document also contains data on the operation of the optic-laser communication channel and the determination of coordinates that were tested during the Lunokhod-2 mission.
During the 306th communication session, Soviet scientists transmitted information through the optic-laser channel to the Moon and back for the first time in history, via a radio channel. The photodetector detected the laser radiation from the ground direction finder, while the on-board equipment of Lunokhod-2 transmitted a radio signal to the earth. This allowed to accurately track the coordinates of Lunokhod-2 from a distance of more than 380,000 kilometres.
The report also talks about the completion of Lunokhod-2 mission. During the 503rd session, the temperature inside the device raised to 43-47 degrees Centigrade, and the connection with the lunar rover was lost for good.
The Luna-21 spacecraft reached the surface of the Moon on January 15, 1973 landing on the eastern edge of the Sea of Clarity, inside the crater of Le Monnier. During four months of work, the Lunokhod rover had covered the distance of 42 kilometres, transmitted 86 panoramas and about 80,000 tele-images of the Moon to the Earth. The vehicle came out of order due to overheating of the equipment inside the case caused by accidental ingress of lunar soil.