Lunar Laser Ranging (LLR)
LLR measures the round-trip travel times of light pulses between stations on the earth and four retroreflectors on the surface of the Moon.
In addition to its value for lunar sciences and the theory of gravitation, LLR is a key IERS technique for connecting reference frames. LLR is used to determine the obliquity of the ecliptic, the orientation of the dynamical frame of the Solar System in the extragalactic reference frame, and long-period nutation and precession.
The envisioned improvements in accuracy (a few millimeters in range) and network distribution (planned stations all around the world) could enhance the LLR contribution to IERS for the next decade.
A description of one of the Lunar Laser Ranging Stations (MLRS) is available on the Web.
In the IERS, SLR is represented by the International Laser Ranging Service (ILRS).