On This Day

Tuesday 17th November 1970

49 years ago

An unmanned Soviet lunar probe, Luna 17, soft-landed in the Sea of Rains on the surface of the moon. Hours later, Lunokhod 1, a self-propelled vehicle controlled by Soviet mission control on earth, rolled out of the Luna landing probe, and became the first wheeled vehicle to travel on the surface of the moon. The vehicle formed of a tub-like compartment with a large convex lid on eight independently powered wheels, was equipped with a cone-shaped antenna, a highly directional helical antenna, four television cameras, and special extendable devices to impact the lunar soil for soil density and mechanical property tests. An x-ray spectrometer, an x-ray telescope, cosmic-ray detectors, and a laser device were also included. The vehicle was powered by a solar cell array mounted on the underside of the lid. Lunokhod was intended to operate through three lunar days but actually operated for eleven lunar days (eleven earth months). The operations of Lunokhod officially ceased on 4 October 1971, the anniversary of Sputnik 1, after having travelled over 10.5 kilometers while taking pictures and performing numerous tests. Luna 17 continued the spate of successes in Soviet lunar exploration begun by Luna 16 and Zond 8. Luna 17 carried Lunokhod 1, the first in a series of robot lunar roving vehicles whose conception had begun in the early 1960s, originally as part of the piloted lunar landing operations. This was the second attempt to land such a vehicle on the Moon after a failure in February 1969. The descent stage was equipped with two landing ramps for the "ascent stage," that is, the rover, to disembark onto the Moon’s surface. The 756-kilogram rover stood about 1.35 meters high and was 2.15 meters across. Each of its eight wheels could be controlled independently for two forward and two reverse speeds. Its top speed was about 100 meters per hour, with commands issued by a five-man team of "drivers" on Earth who had to deal with the 5-second delay. The set of scientific instruments was powered by solar cells (installed on the inside of the hinged top lid of the rover) and chemical batteries. After two mid-course corrections en route to the Moon, Luna 17 entered lunar orbit and then landed on the lunar surface at 03:46:50 UT on 17 November 1970 at 38°17' north latitude and 35° west longitude, about 2,500 kilometers from the Luna 16 site in the Sea of Rains. The Lunokhod 1 rover rolled over the ramps and onto the lunar surface at 06:28 UT. During its 322 Earth days of operation, the rover traveled 10.54 kilometers and returned more than 20,000 TV images and 206 high-resolution panoramas. In addition, Lunokhod 1 performed twenty-five soil analyses with its RIFMA X-ray fluorescence spectrometer and used its penetrometer at 500 different locations. Controllers finished the last communications session with Lunokhod 1 at 13:05 UT on 14 September 1971. Attempts to reestablish contact were finally discontinued on 4 October. In March 2010, the Lunar Reconnaissance Orbiter photographed the landing site of Luna 17, showing the lander and tracks of the rover. In April 2010, the Apache Point Observatory Lunar Laser-ranging Operation team announced that with the aid of these photos, they had found the long-lost Lunokhod 1 rover and had received returns from the laser retroreflector.