Timing Operations and Data Processing in the Goddard Laser Tracking Network

摘要

The NASA Crustal Dynamics Project has deployed Satellite Ranging (SLR) systems and Very Long Baseline Interferometer (VLBI) systems for measurements of global and regional crustal motions and earth rotational parameters. As part of this effort, Bendix Field Engineering Corporation (BFEC) is currently providing engineering and technical support in operations, data collection and data reduction and analysis for NASA's Crustal Dynamics Project. NASA Laser ranging systems are used to determine the range to a target satellite by measuring the flight time of a short pulse of intense light to the target and back. The ranging data can be used for determining satellite orbital parameters, polar motion, earth tidal parameters and the distance between laser ranging system sites. The accuracy of laser ranging is critically dependent upon precise timing. BFEC's current requirements are to maintain synchronization between laser stations, and reference them back to UTC(USNO), to within +/- 1.0 microsecond, with the potential to meet a few hundred nanosecond requirement in the near future. This paper will present the activities and procedures which are used to meet the aforementioned requirements and also, the efforts which are underway at BFEC to improve present performance. The Precision Timing Section (PTS) at BFEC has been responsible for maintaining and reporting time positions for the Goddard Laser Tracking Network (GLTN) for the past twelve years. GLTN's stringent timing requirements have necessitated the development and utilization of advance time transfer and timing data processing techniques. New timing equipment and methods are being tested and developed by PTS to increase BFEC's capabilities in time generation and time synchronization, in close cooperation with NASA and other U.S. government agencies.