Спутники LAGEOS: Лазерная геодинамика и долгосрочное наблюдение Земли.

Scientific research satellites

LAGEOS, Laser Geodynamics Satellite or Laser Geometric Environmental Observation Survey, are a series of two scientific research satellites designed to provide an orbiting laser ranging benchmark for geodynamical studies of the Earth. Each satellite is a high density passive laser reflector in a very stable medium Earth orbit (MEO).

The spacecraft are aluminum covered brass spheres with diameters of and masses of , covered with 426 cube corner retroreflectors, giving them the appearance of disco balls. Of these retroreflectors, 422 are made from fused silica glass while the remaining 4 are made from germanium to obtain measurements in the infrared for experimental studies of reflectivity and satellite orientation. well above low Earth orbit and well below geostationary orbit, at orbital inclinations of 109.8 and 52.6 degrees. Measurements are made by transmitting pulsed laser beams from Earth ground stations to the satellites. The laser beams then return to Earth after hitting the reflecting surfaces; the travel times are precisely measured, permitting ground stations in different parts of the Earth to measure their separations to better than one inch in thousands of miles. The LAGEOS satellites make it possible to determine positions of points on the Earth with extremely high accuracy due to the stability of their orbits. The high mass to area ratio and the precise, stable (attitude independent) geometry of the LAGEOS spacecraft, together with their extremely regular orbits, make these satellites the most precise position references available.

LAGEOS 1 (which is predicted to re enter the atmosphere in 8.4 million years) also contains a 4 in × 7 in plaque designed by Carl Sagan to indicate to future humanity when LAGEOS 1 was launched. The plaque includes the numbers 1 to 10 in binary. In the upper right is a diagram of the Earth orbiting the Sun, with a binary number 1 indicating one revolution, equaling one year. It then shows 268,435,456 years in the past (binary: 228), indicated by a left arrow and the arrangement of the Earth's continents at that time (during the Permian period). The present arrangement of the Earth's continents is indicated with a 0 and both forward and backward arrows. Then the estimated arrangement of the continents in 8.4 million years with a right facing arrow and 8,388,608 in binary (223). LAGEOS itself is shown at launch on the 0 year, and falling to the Earth in the 8.4 million year diagram.