International Laser Ranging Service (ILRS)

Laser ranging activities are organized under the International Laser Ranging Service (ILRS) which provides global satellite and lunar laser ranging data and their derived data products to support research in geodesy, geophysics, Lunar science, and fundamental constants. The ILRS was formed to provide a service to support, through Satellite and Lunar Laser Ranging data and related products, geodetic and geophysical research activities as well as products important to the maintenance of an accurate International Terrestrial Reference Frame (ITRF), which is established and maintained by the International Earth Rotation and Reference Systems Service (IERS). The ILRS develops the necessary global standards/specifications for laser ranging activities and encourages international adherence to its conventions.

The ILRS collects, merges, archives and distributes Satellite Laser Ranging (SLR) and Lunar Laser Ranging (LLR) observation datasets of sufficient accuracy to satisfy the objectives of a wide range of scientific, engineering, and operational applications and experimentation. These datasets are used by the ILRS to generate a number of scientific and operational data products including but not limited to:

  • Earth orientation parameters (polar motion and length of day)
  • Three-dimensional coordinates and velocities of the ILRS tracking stations
  • 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

The accuracy of SLR/LLR data products is sufficient to support a variety of scientific and operational applications including:

  • Realization of global accessibility to and the improvement of the International Terrestrial Reference Frame (ITRF)
  • Monitoring three dimensional deformations of the solid Earth
  • Monitoring Earth rotation and polar motion
  • Support the monitoring of variations in the topography and volume of the liquid Earth (ocean circulation, mean sea level, ice sheet thickness, wave heights, etc.)
  • Tidally generated variations in atmospheric mass distribution
  • Calibration of microwave tracking techniques
  • Picosecond global time transfer experiments
  • Astrometric observations including determination of the dynamic equinox, obliquity of the ecliptic, and the precession constant
  • Gravitational and general relativistic studies including Einstein's Equivalence Principle, the Robertson-Walker b parameter, and time rate of change of the gravitational constant
  • Lunar physics including the dissipation of rotational energy, shape of the core-mantle boundary (Love Number k2), and free librations and stimulating mechanisms
  • Solar System ties to the International Celestial Reference Frame (ICRF)

From: ILRS Terms of Reference, 1998