Performance of the NASA Laser Ranging System in Satellite Tracking

Studies to determine the ranging accuracy of the laser systems at NASA Goddard Space Flight Center have employed both long-arc orbital comparison, using optical and Doppler observations of Geos-I, and predicted trajectory comparison. The long-arc technique compares the ranges measured by the laser with those predicted by a reference orbit computed without using laser data. The second method, utilizing computed trajectory comparisons, adds laser measurements to an orbital solution to demonstrate the improvement from these data in predicting the position of a spacecraft. The pulsed-laser systems have a range accuracy of approximately 2 m, and the range noise is generally less than 1.5 m when measuring at near-earth satellite distances (1000-3500 km). Early results from laser ranging in daylight show range measurements with no appreciable increase in noise over nighttime operations.