Initial Test Results of USNO GPS Time Transfer Unit

Abstract

Summary The U. S. Naval Observatory (USNO), as part of its mission in the field of Precise Time and Time Interval (PTTI), is vitally interested in the development of new concepts, techniques, and equipments for the generation and dissemination of PTTI. The advent of the Global Positioning System (GPS), with its predicted capability for time transfers on a worldwide basis to the ten-nanosecond level, promises to be a vehicle for unprecedented improvements in worldwide timekeeping. The USNO secured funding and coodinated an effort to build a GPS receiver for time transfer. The GPS Time Transfer Unit (GPS/TTU) that was the result of these efforts was initially tested in late 1979 and was found to perform well within the f 100 nanosecond range required in the procurement specification. Additional testing at the USNO was conducted to verify the relationship between Coordinated Universal Time (UTC) and GPS time and to evaluate the performance of the satellites as vehicles for time transfer. The data being gathered are being made available via an automated data link to anyone interested. Analysis of the data gathered to date has revealed several areas of uncertainty that must be resolved if the system is to be used to its fullest potential. Improvements to the GPS/TTU to enhance its operation are also being planned.