LAGEOS-1, -2

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Mission Photos:



Courtesy of NASA

Courtesy of ASI

Mission Objectives:

LAser GEOdynamics Satellite-1 (LAGEOS) was designed by NASA and launched in 1976. It was the first spacecraft dedicated exclusively to high-precision laser ranging and provided the first opportunity to acquire laser-ranging data that were not degraded by errors originating in the satellite orbit or satellite array. LAGEOS-2, based on the LAGEOS-1 design, was built by the Italian Space Agency and was launched in 1992.

There are plans for the launch of LAGEOS-3, which is a joint multinational program with collaboration from France, Germany, Great Britain, Italy, Spain and the United States. Data from LAGEOS-3 would be used to measure, for the first time, a quasi-stationary property of the Earth - its gravitational magnetic dipole moment as predicted by Einstein's theory of general relativity.

Mission Instrumentation:

The LAGEOS satellites are covered with 426 cube corner reflectors with all but four of these reflectors made with fused silica glass. The other four reflectors are made of germanium to obtain measurements in the infrared for experimental studies of reflectivity and satellite orientation.

Dr. Carl Sagan designed a plaque that was installed in LAGEOS-1. The plaque is 4 inches by 7 inches (10 cm by 18 cm) stainless steel plate. The spacecraft carries two identical copies included in its interior. In its upper center it displays the simplest counting scheme, binary arithmetic. The numbers one to ten in binary notation are shown. At upper right is a schematic drawing of the Earth in orbit around the Sun, and an arrow indicating direction of motion. The arrowhead points to the right, the convention adopted for indicating the future. All arrows accompanying numbers are "arrows of time". Under the Earth's orbit is the binary number one, denoting the period of time used on the plaque -- one revolution of the Earth, or one year. The remainder of the LAGEOS plaque consists of three maps of the Earth's surface. The first map denotes the Earth 268 million years in the past. All the continents are shown together in one mass. The close fit of South America into West Africa was one of the first hints that continental drift actually occurs. The middle map represents the zero point in time for the other two maps. It displays the present configuration of the planet. The final map shows the Earth's surface 8.4 million years from now -- very roughly the estimated lifetime of the LAGEOS. Many important changes in the Earth's surface are shown, including the drift of California out into the Pacific Ocean. Whoever comes upon the LAGEOS plaque needs only compare a current map of the Earth's geography with that in the lower two maps to calculate roughly the difference between his time and ours. Drift rates of about an inch per year can, in fact be estimated by comparing the bottom two maps. The same objective of LAGEOS and the method of telling time on the plaque are identical. (from NASA/John R. Bannister, February 1977 NASA Aerospace Education Services Project Oklahoma State University, Stillwater, Oklahoma)

Mission Parameters:



LAGEOS-1 LAGEOS-2 Sponsor: United States United States and Italy Expected Life: many decades many decades Primary Applications: geodesy geodesy COSPAR ID: 7603901 9207002 SIC Code: 1155 5986 Satellite Catalog (NORAD) Number: 8820 22195 Launch Date: May 4, 1976 October 22, 1992 RRA Diameter: 60 cm 60 cm RRA Shape: sphere sphere Reflectors: 426 corner cubes 426 corner cubes Orbit: circular circular Inclination: 109.84 degrees 52.64 degrees Eccentricity: 0.0045 0.0135 Perigee: 5,860 km 5,620 km Period: 225 minutes 223 minutes Weight: 406.965 Kg 405.38 kg

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