TLRS-4 Laser Ranging System

The University of Hawaii IfA is operating and maintaining the TLRS-4 at the Haleakala High Altitude Observatory Site (HO) at Haleakala on the island of Maui under a contract with NASA/GSFC.

Laser Ranging has been part of UH IfA operations at HO since 1972. The LURE Observatory was established at HO under contract to NASA, and was operated by the UH IfA during the period 1972-2004. During this time, LURE provided NASA/GSFC with extremely accurate measurements of the distance to the Moon and to artificial Earth satellites. This is accomplished by bouncing very short pulses of laser light off special reflectors left on the Moon by the Apollo astronauts and installed on satellites orbiting the earth. By accurately timing the round-trip time of flight of these pulses, distances can be computed and precise orbits determined. These data are used to acquire fundamental information about the geophysical processes of the Earth and the Earth-Moon system. For a more complete description of LR, visit the ILRS web site.

The LURE Observatory contract expired in July 2004, and the site is presently being used by the Pan-STARRS project. The primary rationale for the TLRS-4 at HO is to maintain the time-series of SLR data produced by LURE. This is critical to the investigation of the long period geophysical phenomena being studied. Further, the loss of the only SLR site in the Northern Pacific Ocean has degraded the accuracy of satellite orbits derived from the data produced by the worldwide system of SLR sites.

The TLRS-4is a fully operational SLR system contained in a 21.8 x 8.3 x 7.8 foot trailer. A support trailer of similar size, but on wheels, will complete the system. Honeywell Technology Solutions Inc. built the system under contract to NASA/GSFC.

The electronics trailer weighs 15,000 pounds, and is set on an existing 24 x 15 x 1 foot concrete pad located approximately 40 meters west of the Mees Observatory. The support trailer is parked close to the western wall of the Mees Observatory.