The Lunokhods were remote-controlled moon rovers that the Soviet Luna spacecraft successfully
carried to the Moon's surface
in 1970 and again in 1973. The purpose of the vehicles was to roll across the Moon's
surface, sending back panoramic stereoscopic television images and making soil measurements. In shape and size the Lunokhods resembled bathtubs with four wheels on each long side. Total weight was about 900 kg (2,000 lb). A lid over the roof was raised in the daytime to expose solar power cells. A small radioisotope unit was used to maintain a survivable temperature. The first successful Lunokhod (
carried by Luna 17) landed in the Mare Imbrium on Nov. 17, 1970. It operated for 11 months under the control of a 5-man team at a communications center near Moscow and covered a total of 10 km (6 mi) while crisscrossing the landing site. The second Lunokhod (carried by Luna 21) landed on the Moon on Jan. 16, 1973, inside the crater Le Monnier in the Mare Serenitatis. It covered 35 km (22 mi) in 5 months before apparently becoming stuck while exploring a deep ravine.