Satellite Laser Ranging Techniques for Monitoring Crustal Dynamics

The precision of laser systems for ground-based ranging to Earth satellites has recently been pushed to reach the sub-decimeter level. It is anticipated that a precision of a few centimeters in a single range will be obtainable within the next five years. This feature makes satellite laser ranging a candidate techniques for monitoring regional or global relative crustal motions as e.g. implied by plate tectonics hypotheses. The technique, its present state of art and its foreseen development are briefly reviewed, both as regards ranging to the moon and to artificial satellites. Attention is paid to the merits of laser ranging relative to those of complementary and/or competing space techniques. Satellite-borne laser ranging to Earth- based targets is a concept currently in study Another new concept to consider is that of a highly mobile laser ranging device to contribute to the monitoring of pre- and post-seismic creep Several approaches for accurate relative positioning of crustal points by laser ranging to satellites have been considered in view of recovering relative movements at velocities in the 1 to 10 cm/year range. Although sub-meter relative positioning has in practice been achieved over distances up to some thousands of kilometers, as yet most estimates of precision and reliability of dedicated geodetic networks are the results of simulated experiments. Some of the more significant of these results are reviewed. These demonstrate the potential capabilities of the satellite laser ranging technique to recover relative crustal motions, provided the required further progress of measurement precision to the level of a few centimeters in a field- operational mode can indeed be made.