Lunokhod 2

Lunokhod 2 was the second of two unmanned lunar rovers landed on the Moon by the Soviet Union as part of the Lunokhod program.

*Launch Date/Time: 1973-01-08 at 06:55:38 UTC
*On-orbit dry mass: 4850 kg (4.77 long tons)

The Luna 21 spacecraft landed on the Moon and deployed the second Soviet lunar rover (Lunokhod 2). The primary objectives of the mission were to collect images of the lunar surface, examine ambient light levels to determine the feasibility of astronomical observations from the Moon, perform laser ranging experiments from Earth, observe solar X-rays, measure local magnetic fields, and study mechanical properties of the lunar surface material.

Lunokhod 2 rover and subsystems

The rover stood 135 cm (4 ft 5 in) high and had a mass of 840 kg (1,850 lb). It was about 170 cm (5 ft 7 in) long and 160 cm (4 ft 11 in) wide and had 8 wheels each with an independent suspension, motor and brake. The rover had two speeds, ~1 km/h and ~2 km/h (0.6 mph and 1.2 mph). Lunokhod 2 was equipped with three television cameras, one mounted high on the rover for navigation, which could return high resolution images at different rates—3.2, 5.7, 10.9 or 21.1 seconds per frame (not frames per second). These images were used by a five-man team of controllers on Earth who sent driving commands to the rover in real time. Power was supplied by a solar panel on the inside of a round hinged lid which covered the instrument bay, which would charge the batteries when opened. A polonium-210 isotopic heat source was used to keep the rover warm during the long lunar nights. There were 4 panoramic cameras mounted on the rover. Scientific instruments included a soil mechanics tester, solar X-ray experiment, an astrophotometer to measure visible and ultraviolet light levels, a magnetometer deployed in front of the rover on the end of a 2.5 m (8 ft 2 in) boom, a radiometer, a photodetector (Rubin-1) for laser detection experiments, and a French-supplied laser corner reflector. The lander and rover together massed 1814 kg.

Mission profile

The SL-12/D-1-e launcher put the spacecraft into Earth parking orbit followed by translunar injection. On January 12 1973, Luna 21 was braked into a 90 by 100 km (approx. 56 by 62 mile) orbit about the Moon. On January 13 and January 14, the perilune was lowered to 16 km (10 mi) altitude.

Landing and surface operations

On January 15 after 40 orbits, the braking rocket was fired at 16 km (10 mi) altitude, and the craft went into free fall. At an altitude of 750 m (2,460 ft) the main thrusters began firing, slowing the fall until a height of 22 m (72 ft) was reached. At this point the main thrusters shut down and the secondary thrusters ignited, slowing the fall until the lander was 1.5 m (5 ft) above the surface, where the engine was switched off. Landing occurred at 23:35 UT in Le Monnier crater at 25.85 degrees N, 30.45 degrees E. The lander carried a bas relief of Lenin and the Soviet coat of arms.

After landing, the Lunokhod 2 took TV images of the surrounding area, then rolled down a ramp to the surface at 01:14 UT on January 16 and took pictures of the Luna 21 lander and landing site, driving for 30 meters. After a period of charging up its batteries it took more pictures of the site and the lander, and then set off to explore the moon.

The rover would run during the lunar day, stopping occasionally to recharge its batteries via the solar panels. At night the rover would hibernate until the next sunrise, heated by the radioactive source.

* January 18, 1973 to January 24, 1973: The rover drives 1,260 metres

* February 8, 1973 to February 23, 1973: The rover drives 9,086 metres further

* March 11, 1973 to March 23, 1973: The rover drives 16,533 metres further

* April 9, 1973 to April 22, 1973: The rover drives 8,600 metres further

* May 8, 1973 to June 3, 1973: The rover drives 880 metres further

End of mission

On June 4, 1973 it was announced that the program was completed, leading to speculation that the vehicle probably failed in mid-May or could not be revived after the lunar night of May-June.

More recently, Alexander Basilevsky related an account where on May 9, 1973, the rover's open lid touched a crater wall and became covered with dust. When the lid was closed for the lunar night, this dust (a very good insulator) was dumped on to the radiators, The following lunar day, controllers saw the internal temperature of the Lunokhod climb as it was unable to cool itself, eventually rendering the rover inoperable. [ [http://www.airspacemag.com/space-exploration/other-moon.html "The Other Moon Landings", by Andrew Chaikin, (Air & Space Magazine, February/March 2004, pages 30-37] ] .

Results

Lunokhod 2 operated for about 4 months, covered 37 km (23 miles) of terrain, including hilly upland areas and rilles, and sent back 86 panoramic images and over 80,000 TV pictures. Many mechanical tests of the surface, laser ranging measurements, and other experiments were completed during this time.

Current status

Lunokhod 2 continues to be detected by lunar laser ranging experiments and its position is known to sub-meter accuracy. [citeweb|title=Lunar Geophysics, Geodesy, and Dynamics|url=http://ilrs.gsfc.nasa.gov/docs/williams_lw13.pdf|publisher=ilrs.gsfc.nasa.gov|accessdate=2008-02-06]

ee also

* Luna 21
* Lunar Laser Ranging Experiment
* Lunokhod 1

References

External links

* [http://www.zarya.info/Diaries/Luna/Luna21.php Zarya - Lunokhod 2 chronology]

* [http://selena.sai.msu.ru/Home/Spacecrafts/Lunokhod2/lunokhod2e.htm Lunar and Planetary Department Moscow University Lunokhod 2 page]
* [http://nssdc.gsfc.nasa.gov/nmc/tmp/1973-001A.html NSSDC Master Catalog: Spacecraft: Luna 21/Lunokhod 2]

* [http://www.mentallandscape.com/C_CatalogMoon.htm Don P. Mitchell's catalog of Soviet Moon Images] including many from Lunokhod 2
* [http://vsm.host.ru/e_lunhod.htm Lunokhod 2 information and VRML models at the Virtual Space Museum]