Mission Type: Sample Return
Launch Vehicle: 8K82K + Blok D (Proton-K no. 258-01)
Launch Site: NIIP-5 / launch site 81P; Tyuratam (Baikonur Cosmodrome),USSR
Spacecraft Mass: c. 5,750 kg
Spacecraft Instruments: 1) stereo imaging system 2) remote arm for sample collection 3) radiation detector; and 4) radio altimeter
References:
Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000, Monographs in Aerospace History No. 24, by Asif A. Siddiqi

National Space Science Data Center, http://nssdc.gsfc.nasa.gov/

Solar System Log by Andrew Wilson, published 1987 by Jane's Publishing Co. Ltd.

This was the eighth Soviet spacecraft launched to return lunar soil to Earth. It was evidently sent to complete the mission that Luna 18 had failed to accomplish.

After a 4.5-day flight to the Moon, which included a single midcourse correction on 15 February, Luna 20 entered orbit around the Moon on 18 February. Initial orbital parameters were 100 x 100 kilometers at 65? inclination. Three days later, at 19:13 UT, the spacecraft fired its main engine for 267 seconds to begin descent to the lunar surface. A second firing further reduced velocity before Luna 20 set down safely on the Moon at 19:19 UT on 21 February 1972 at coordinates 3°32' north latitude and 56°33' east longitude, only 1.8 kilometers from the crash site of Luna 18.

After collecting a small sample of lunar soil, the spacecraft's ascent stage lifted off at 22:58 UT on 22 February and quickly accelerated to 2.7 kilometers per second velocity-sufficient to return to Earth. The small spherical capsule eventually parachuted down safely on an island in the Karkingir River, 40 kilometers north of the town of Dzhezkazgan in Kazakhstan, at 19:19 UT on 25 February 1972.

The 55-gram soil sample differed from that collected by Luna 16 in that the majority (50 to 60 percent) of the rock particles in the newer sample were ancient anorthosite (which consists largely of feldspar) rather than the basalt of the earlier one (which contained about 1 to 2 percent of anorthosite). Like the Luna 16 soil, samples of the Luna 20 collection were shared with American and French scientists.