The International Laser Ranging Service and its support for GGOS and Earth Sciences

Michael Pearlman⁽¹⁾, Carey Noll⁽²⁾, Jan McGarry⁽³⁾, Werner Gurtner⁽⁴⁾ and Erricos Pavlis⁽⁵⁾

⁽¹⁾ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, United States
⁽²⁾ NASA Goddard Space Flight Center, Code 690, Greenbelt, MD 20771, United States
⁽³⁾ NASA Goddard Space Flight Center, Code 694, Greenbelt, MD 20771, United States
⁽⁴⁾ University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland
⁽⁵⁾ University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, United States

Abstract

The International Laser Ranging Service (ILRS) was established in September 1998 within the IAG to support programs in geodetic, geophysical, and lunar research activities and to provide data products to the International Earth Rotation and Reference Frame Service (IERS) in support of its prime objectives. The ILRS develops the standards and specifications necessary for product consistency and the priorities and tracking strategies required to maximize network efficiency. The ILRS network consists of more than forty SLR stations, routinely tracking nearly thirty retroreflector-equipped satellites and the Moon in support of user needs. The Service collects, merges, analyzes, archives and distributes satellite and lunar laser ranging data to satisfy a variety of scientific, engineering, and operational needs and encourages the application of new technologies to enhance the quality, quantity, and cost effectiveness of its data products. The ILRS works with the global network to improve station performance, new satellite missions in the design and building of retroreflector targets to maximize data quality and quantity, and science programs to optimize scientific data yield. The ILRS Central Bureau maintains a comprehensive web site (http://ilrs.gsfc.nasa.gov) as the primary vehicle for the distribution of information within the ILRS community.

Through the continuous tracking of LAGEOS-1 and -2, the ILRS helps to maintain the Terrestrial Reference Frame (TRF) by providing time-varying geocenter coordinates and scale (GM). ILRS data are used to generate scientific and operational data products such as static and time-varying coefficients of the Earth's gravity field models, tides, Earth orientation parameters (polar motion and length of day), and three-dimensional station coordinates and velocities. The data are also used to determine precision satellite orbit ephemerides (for calibration and validation of satellite altimetry), fundamental physical constants, lunar ephemerides and librations, and lunar orientation parameters. SLR also provides tracking data for special engineering missions. The ILRS continues to encourage new missions with high precision orbit requirements to include retroreflectors to improve or strengthen overall orbit precision, and to provide important intercomparison and calibration data with onboard microwave navigation systems.

During the last several years new SLR stations have enhanced the global coverage of the network, particularly in the Southern Hemisphere. Work continues at several institutions on ground system development toward the next generation laser ranging system with the introduction of kilohertz pulse repetition rates, greater automation, and greater eye safety. Work also continues on the development of new lighter weight retroreflector arrays.