SLR

Satellite Laser Ranging (SLR) is a fundamental measurement technique used by NASA to support both national and international programs in Earth dynamics, ocean and ice surface altimetry, navigation, and positioning. SLR utilizes a global network of stations to measure distances by bouncing very short pulses of laser light off special reflectors installed on satellites orbiting the earth, and also left on the Moon by the Apollo astronauts and Soviet rovers. By accurately timing the round-trip time of flight of these pulses, distances can be computed and precise orbits determined. This data is then used to acquire fundamental information about the geophysical processes of the Earth and the Earth-Moon system.

TLRS-4 Laser Ranging System - HawaiiGSFC has five trailer-based Mobile Laser Ranging Stations (MOBLAS) in operation at fixed sites for over thirty years. Two compact Transportable Laser Ranging Systems (TLRS) are operational at the University of Hawaii and in Peru. In addition, the University of Texas operates a high performing Observatory SLR system at the McDonald Observatory site located in the Davis Mountains of West Texas, which also has lunar ranging capabilities.  A prototype Next Generation Satellite Laser Ranging (NGSLR) station is also operational supporting the NASA Lunar Reconnaissance Orbiter around the Moon.

MOBLAS-8 Laser Ranging System - TahitiNASA relies on international partners for the foreign sites. The Australians operate MOBLAS-5 in Yarragadee, Australia; the South Africans operate the MOBLAS-6 at Hartebeesthoek Radio Astronomical Observatory in Hartebeesthoek, South Africa; and the University of French Polynesia/CNES operates MOBLAS-8 in Tahiti. Under these partnerships, NASA provides the SLR system, training, engineering support, and parts to maintain SLR operations, while the host country provides the site, local infrastructure, and operating crew.

NASA GSFC was the first to successfully demonstrate laser ranging to satellites in 1964. The NASA SLR Network has been fully operational in the field for over thirty years. During this time, the Network has seen many modifications and upgrades to maintain system operations and more importantly, to increase the quantity and quality of data products. Working as part of the International Laser Ranging Service (ILRS), GSFC has played a crucial role improving ranging precision by a factor of a thousand from a few meters to a few millimeters.

NASA plans enable the system operations and performance to be maintained at productive levels. Recently, the MOBLAS, TLRS, and MLRS (University of Texas SLR system) have received both hardware and software upgrades to enhance operability.

In summary, the SLR Network consists of eight NASA operated, partner operated, and University operated stations covering North America, the west coast of South America, the Pacific, South Africa, and Western Australia.  The NASA SLR Network continues to provide over a third of the total data volume in the ILRS as well as sub-cm accuracy ranging data.

SLR Locations Table