Satellite laser ranging | ||||
Satellite laser ranging | Automatic translation | Updated June 01, 2013 | ||
The Earth moves around the ecliptic around the sun at an average speed of 107 218.8 km/h (between 29.291 km/s and 30.287 km/s). At the same time the Earth rotates on itself around an axis at the speed (at the equator) of 1674.364 km/h (465 m/s). Our natural satellite (moon) and artificial turn at different speeds, 1.17 km/s for the Moon, 3.88 km/s for the GPS satellites or 7.68 km/s for ISS. Despite these relative velocities it is possible to accurately measure the distance between our satellite and Earth. For this we use the satellite laser ranging (SLR). | Another technique as the technique of Laser Moon (LLR) is used to determine the obliquity of the ecliptic, and the orientation of the solar system in the extragalactic reference. Image: Satellites LAGEOS (Laser Geodynamics Satellite) are artificial satellites in Earth orbit. Contituted by a brass ball covered with aluminum on which were placed 426 retroreflectors rhombohedric (cube corners), they are entirely passive. Placed on a circular orbit mean (5 900 km altitude) and very massive (406 kg for a 60-cm diameter), they are very stable and remain in orbit for 8.4 million years. Also, are they filled a time capsule giving the position, the current and projected continents. 422 are cube corner blocks made of quartz glass and 4 germanium in order to reflect the infrared and allow the study of variation of the altitude of the satellite. 35 ground stations participating in distance measurements by calculating the time taken by a laser beam to return to its point of emission. The measurement accuracy is centimetric and can measure the movement of tectonic plates with comparable accuracy. There are other satellites equipped with retro-reflectors (ERS, Jason, Starlet, Etalon, two GPS satellites (-35, -36,...) and five retro-reflectors were deposited on the Moon. | Image: Laser ranging satellite. |