G - I
ILRS
The International Laser Ranging Service (ILRS) provides global satellite and lunar laser ranging data and their related products to support geodetic and geophysical research activities as well as IERS products important to the maintenance of an accurate International Terrestrial Reference Frame (ITRF). The service develops the necessary global standards/specifications and encourages international adherence to its conventions. The ILRS is one of the space geodetic services of the International Association of Geodesy (IAG). The ILRS collects, merges, archives and distributes Satellite Laser Ranging (SLR) and Lunar Laser Ranging (LLR) observation data sets of sufficient accuracy to satisfy the objectives of a wide range of scientific, engineering, and operational applications and experimentation. These data sets are used by the ILRS to generate a number of scientific and operational data products including: Earth orientation parameters (polar motion and length of day) Station coordinates and velocities of the ILRS tracking systems Time-varying geocenter coordinates Static and time-varying coefficients of the Earth's gravity field Centimeter accuracy satellite ephemerides Fundamental physical constants Lunar ephemerides and librations Lunar orientation parameters Information provided by http://ilrs.gsfc.nasa.gov/about_ilrs/index.html