Lunar Polar Mission applying Laser Power Transmission
- Paper number
IAC-05-A3.4.09
- Author
Dr. Nobuyuki Kaya, Kobe University, Japan
- Coauthor
Mr. Christian Schaefer, Kobe University, Japan
- Year
2005
- Abstract
In the last 10 years the lunar poles have been intensively studied because of the possible existance of water-ice deposits in permanent shadowed craters. Results provided by the lunar missions “Clementine” and “Prospector” indicate up to 3 billion tons of ice may be present. However the results are still inconsistent and not conclusive. A rover mission to a moon crater would bring clear evidence for ice deposits on the moon. Equipped with spectrometers and a drill, it could probe the moon’s surface down to approx. a meter deep. It has been suggested that ice is probably covered by a regoltih layer of some cm. Because of the permanent shadow inside the crater, the rover would have to be powered by RTG’s. But to become independant another technology is suggested which perfectly fits to this mission: Laser Power Transmission (LPT). In the last 2 years LPT- experiments have been demonstrated on km distances and even an independant finding and beam tracking system using active control loops. In only a few years this technology could be developed up to 20 km distance having an overall efficiency of about 10This paper describes the finding and control process of the rover. A pilot signal coming from the rover indicates the position very roughly. The laser beam scans the indicated area in order to hit laser reflectors attached at the rover. The exact position is determined by measuring the intensity profile of the beam spot on the cell area. The control loop is closed by an optical link rover - station which enables communication as well as a continuous rover tracking. Two mission scenarios are compared: 1st A polar orbiter on an excentric orbit with apogee over the rovers position collects sunlight energy to power a laser. Each time the rover is in sight, it will be powered by the satellite’s laser beam. The altitude of the satellite has to be high enough to power the rover’s batteries and to ensure power during its operation time. A calculation using realistic parameters for the power of the laser beam and the rover’s energy consumption in operation and standby mode reveals high relative velocities as well as a apogee’s altitude of at least several hundred km and subsequently a high transmission distance. These requirements were assumed as too high for a first LPT space mission. 2nd A station is placed onto a permanent illuminated area near a shadowed crater to collect permanently sunlight energy. Even that the most promising crater has still to be determined by future lunar missions, such illuminated regions (at least in the lunar winter) can be found near the south pole. Subsequently the crater Shackelton (89°S,110°E) is applyed for this case. Beside the station, small relay stations are deployed in the area. The rover, deployed by the power station, heads to the crater while it is powered by the station’s laser beam. The beam is split into three parts to hit the rover from three different directions by using the relay stations. This principle increases the reliability, as the connection laser-rover is important. Since scenario no. 2 is more realistic anyway, it allows to implement a rover’s positioning system. A small relay satellite will catch characteristic periodical signals sent by each (relay) station to determine their relative and absolute positions. The rover’s position can be determined by catching the same signals and using the satellite’s information of the station’s positions.
- Abstract document
- Manuscript document
IAC-05-A3.4.09.pdf (🔒 authorized access only).
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