Accession Number : ADP009105

Title :   The Use of the AOA TTR-4P GPS Receiver in Operation at the BIPM for Real-Time Restitution of GPS Time,

Corporate Author : NATIONAL AERONAUTICS AND SPACE ADMINISTRATION GREENBELT MD GODDARD SPACE FLIG HT CENTER

Personal Author(s) : Thomas, Claudine

Report Date : 02 DEC 1993

Pagination or Media Count : 12

Abstract : The Global Positioning System is an outstanding tool for the dissemination of time. Using mono-channel C/A-code GPS time receivers, the restitution of GPS time through the satellite constellation presents a peak-to-peak discrepancy of several tens of nanoseconds without SA but may be as high as several hundreds of nanoseconds with SA. As a consequence, civil users are more and more interested in implementary hardware and software methods for efficient restitution of GPS time, especially in the framework of the project of a real-time prediction of UTC, UTCp, which could be available in the form of time differences UTCp - GPS time. Previous work, for improving the real-time restitution of GPS time with SA, to the level obtained without SA, focused an the implementation of a Kalman filtering based on past data and updated at each new observation. An alternative solution relies upon the statistical features of the noise brought about by SA: it has already been shown that the SA noise is efficiently reduced by averaging data from numerous satellites observed simultaneously over a sufficiently long time. This method has been successfully applied to data from a GPS time receiver, model AOA TTR4P, connected to the caesium clock kept at the BIPM. This device, a multi-channel, dual-frequency, P-code GPS time receiver, is one of the first TTR-4P units in operation in a civil laboratory. Preliminary comparative studies of this new equipment with conventional GPS time receivers are described in this paper.

Descriptors :   *GLOBAL POSITIONING SYSTEM, *TIME STANDARDS, *INFORMATION TRANSFER, CHANNELS, GLOBAL, KALMAN FILTERING, OBSERVATION, PREDICTIONS, RECEIVERS, TIME, UNCERTAINTY, NAVIGATION SATELLITES, ATOMIC CLOCKS, CESIUM, TIME INTERVALS.

Subject Categories : Test Facilities, Equipment and Methods

Distribution Statement : APPROVED FOR PUBLIC RELEASE