On the Effective Use of Lunar Ranging for the Determination of the Earth's Orientation

Abstract

Lunar ranging data have been routinely available since September of 1970, but many problems of a varying nature have delayed the establishment of a world-wide lunar ranging network. As a result, we must re-examine the role which this program can play in the determination of the Earth's rotation and polar motion. Although there are many technical difficulties now inhibiting the widespread use of this technique there seems little doubt but that we can overcome these problems and achieve routine, accurate orientation determinations. The more difficult questions concern how an Earth rotation campaign should now be configured to use the equipment and resources in the best way.Despite considerable progress by other techniques, the failure to develop a lunar capability for Earth orientation determinations would result in a serious loss of information. Lunar monitoring of long-term effects in the Earth's rotation rate and the relationship of the lunar orbital parameters to a stellar reference frame are two tasks for which there is little redundancy. However, the most cost-effective usage of station resources may not require daily measures, but only periodic, accurate snapshots of the Earth's rotational position relative to the Moon. If some satellite laser ranging facilities could treat the Moon as an object of opportunity, but were able to elevate the program to priority status when global conditions were favorable, the incremental cost of gathering the required lunar data might be drastically reduced. Even though these cost savings could not be achieved without daily communication between cooperating stations, such a detailed interaction is not unreasonable to consider.