Tests of LARES Cube Corner Reflectors in simulated space environment.
- Paper number
IAC-10.C2.6.11
- Author
Prof. Antonio Paolozzi, University of Rome “La Sapienza”, Italy
- Coauthor
Prof. Ignazio Ciufolini, Università del Salento, Italy
- Coauthor
Prof. Luigi Schirone, University of Rome “La Sapienza”, Italy
- Coauthor
Prof. Isidoro Peroni, Scuola di Ingegneria Aerospaziale, Italy
- Coauthor
Mr. Claudio Paris, University of Rome “La Sapienza”, Italy
- Year
2010
- Abstract
LARES satellite will be launched with the maiden flight of the European new launch vehicle VEGA. The launch is foreseen sometimes in year 2011. The satellite is devoted to test a particular aspect of General Relativity: the Lense-Thirring effect. Tracking of the satellite is performed through laser ranging using laser pulses reflected by the 92 Cube Corner Reflectors (CCRs) mounted on the satellite. Objective of the mission is to measure the effect with a low error that can be reduced at a level of 1%. Such a demanding task implies very stringent requisite on the satellite. One of this is related to the lower orbit with respect to the companion LAGEOS satellites. Non gravitational perturbations at 1450 km are higher than those at 6000 km orbit of LAGEOS satellites. For this reason the satellite has been manufactured with a surface-to-mass ratio 2.7 times higher than the LAGEOS satellites. The thermo-optical surface properties of the tungsten alloy used for the satellite bring LARES at a sensibly higher temperature than the LAGEOS satellites. A concern arose about the possibility of having too high gradients on the CCRs of LARES that can prevent the laser pulse to go back to the emitting ground station once the satellite is in orbit. About 120 LARES CCRs have been already tested in air at room temperature and accepted for flight. But this fact as well as the fact that the experience on previous laser ranged satellites has demonstrated that the CCRs work perfectly at different orbits and even on the Moon does not guarantee that LARES CCRs will work. First theoretical calculations were performed on the deformed CCRs that demonstrated that the signal of the returning laser pulse degrades by about 50% and therefore still a very strong signal is available on the ground. However due to the importance of the issue a specific test is required. For this purpose some specimens of tungsten alloys for housing a CCR with the same mounting system used for the satellite and a thermo-vacuum chamber are being built. The specimens will be suspended inside the chamber. Also a Far Field Diffraction Pattern (FFDP) optical circuit will be assembled outside the chamber. An infrared source will simulate the Earth. A mechanical feedthrough will allow to move the CCR alternatively from the simulated sunlight, to the Earth and to the laser beam for FFDP measurement. Test results will be presented.
- Abstract document
- Manuscript document
IAC-10.C2.6.11.pdf (🔒 authorized access only).
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