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Newest Moon-Bound Spacecraft and oldest Lunokhod to help laser study for safer landing sites on the Moon

by Rus Abz 2011-11-08 13:33

Lunar Retroreflector arraysSolar-powered Gravity Recovery And Interior Laboratory Moon-Bound Spacecraft program GRAIL will create a gravity map of the moon using two spacecraft that orbit at very precise distances. The mission will enable lunar scientists to learn about the moon's internal structure and composition. More accurate knowledge of the moon's gravity patterns gives researchers a better understanding of its origin and could be used to  choose safer landing sites for future lunar missions.

USSR Lunokhod roverThe lessons learned from lunar exploration history since Soviet Lunokhod-1 rover began its journey on the surface of the moon back in in 1970 point out the top importance of the safe landing spot for the mission. The Lunokhod-1 had an extremely robust and reliable design innovated by group of talented armored vehicle engineers featuring eight independently controlled motor-wheels, firmer suspension, electromechanical transmission with individual drive wheels, sophisticated braking system, power automation, and a set of information-measuring sensors providing the readings for the control of the chassis of the Lunar apparatus. To be able to work in vacuum a special fluoride based lubricant was used for the mechanical parts and the electric motors (one in each wheel hub) were enclosed in pressurized containers. Thanks to wide use of titanium alloys in the design of the Lunokhod-1 lunar chassis the strict weight limit requirements were met with the total weight of self-propelled chassis less than 85 kilograms.

On November 17, 1970, the Soviet spacecraft Luna 17 delivered the lunar rover Lunokhod-1 onto the surface of the moon. For 11 months after, controlled in real-time by a human team in Moscow, it explored seven miles of the lunar surface. Sending back reams of data, it was considered to be one of the biggest successes of the little-known Soviet lunar exploration program. The rover would run during the lunar day, stopping occasionally to recharge its batteries via the solar panels. At night the rover hibernated until the next sunrise, heated by the radioactive source. The extreme temperature changes on the moon has led to the eventual degradation of the normal working temperature inside the main body containing the telemetry and remote control equipment. Once the internal optimal temperature in the hermetic body of the rover dropped lower than several degrees of Celsius the Lunokhod-1 ceased transmitting. Lunokhod-1 was intended to operate through three lunar days, equal approximately to tree Earth months, but the robust design and high survivability of the apparatus allowed the Lunokhod rover operate for eleven lunar days.

In 1993 the original Lunokhod-1, together with the landing stage of the Soviet spacecraft station Luna-17 was spotted by the Lavochkin Association at Sotheby's auction. At the starting price of $5000 the first lunar tractor was sold for $68,500. According to Russian press reports at the time, the buyer of the Lunokhod-1 was the son of one of the American astronauts. Delivery of the purchased property from the moon was designated to the buyer's responsibility at buyer's expense.

Recently NASA's Lunar Reconnaissance Orbiter has found the Lunokhod-1 rover location on the moon’s surface. After 41 years of withstanding the harsh lunar temperature conditions the first Soviet rover is still in good shape and can reflect laser beams back to Earth as if it were brand new. The Orbiter pinpointed the Lunokhod-1 precise coordinates. Now that after more than three decades the location is established, pulses of laser light were sent to Lunokhod-1 from the 3.5 meter telescope at the Apache Point Observatory in New Mexico. Amazingly, the rover’s retro-reflector sent the pulses back to the observatory bright and clear at 2,000 photons level. The rover was equipped with small retroreflector arrays each consisting of 14 corner cubes of triangular configuration. Once pinpointed the Lunokhod retroreflector arrays work perfectly fine responding to laser beam pulses as they are brand new.  

Gravity Recovery And Interior Laboratory NASALunokhod 1 was followed by a second rover, Lunokhod 2, in 1973. Its location has long been known, and its retro reflector has routinely been used for Earth-based scientific studies. The best signal from Lunokhod-2 in several years of effort is 750 return photons. The difference could be explained by the emergency situation when the second rover got caught into the lunar crater. At the time GPS navigation systems were not mature enough to be used on board of lunar rover. Without global positioning system aid the rover relied solely on the on-board camera vision. The lunar rover driver explained: "It happened when driving in difficult conditions inside one of the craters. On the wall of the crater there was another one, secondary, small crater. While maneuvering to get out of the first crater remote operator and driver crew made the decision to back up the rover. It so happened that cover the solar panel hit into a wall of the second crater which was invisible to the cameras, as they only looked forward. The solar panel got a lot of dust and debris. After the panel was closed the moon dust and moon soil affected the optical reflector system, the Lunar Retroreflector arrays, the cooling and heating system and disturbed the overall thermal regime of the vehicle”. The lunar vehicle seized its operation soon after.  

Both Lunokhod 1 and Lunokhod 2 are part of an ongoing laser ranging study of the moon. By measuring the time it takes for laser pulses to reach various locations on the moon and record the reflection, in time researchers will know the Moon orbit with millimeter precision. The laser handshake with Lunokhod 1 and Lunokhod 2 is very important for future lunar missions. Put together with the results of the upcoming Gravity Recovery And Interior Laboratory Moon-Bound Spacecraft research of the safe landing sites on the surface of the Moon, the future lunar expeditions could avoid dangerous neighborhood of hidden craters and obstacles which may increase risks for the safe exploration of our closest space neighbor by lunar vehicles and finding more about Moon surface, its internal structure and composition. 

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