The Use of Precise Ephemerides, Ionospheric Data and Corrected Antenna Coordinates in a Long-Distance GPS Time Transfer
Abstract
Over intercontinental distances the accuracy of GPS time transfers ranges from 10 to 20 ns. The principal error sources are the broadcast ionospheric model, the broadcast ephemerides and the local antenna coordinates. Previous work has already shown the impact of correcting each of these error sources individually, using either measured ionospheric delays, precise GPS satellite ephemerides, or improved antenna coordinates. Ionospheric delay measurements can be provided by dual frequency codeless ionospheric calibrators Precise GPS satellite ephemerides are now available from the U.S. Defense Mapping Agency (DMA), and others. GPS receiver antenna coordinates should be accurately linked to stations of the IERS Terrestrial Reference Frame. If such a link is not available from geodetic methods, accurate differential, between GPS antennas, can be realized over short distances, using the BIPM method. For the first time, the three major error sources for GPS time transfer can be reduced simultaneously for a particular time link. Ionospheric measurement system of the NIST type are now operating on a regular bask at the National Institute of Standards and Technology in Boulder (Colorado, USA) and at the Paris Observatory in Paris (France). Broadcast ephemerides are currently recorded for time-transfer track between these sites, this being necessary for using precise ephemerides. At last, corrected local GPS antenna coordinates are now introduced in GPS receivers at both sites. This paper shows the improvement in precision for this long-distance time comparison resulting from the reduction of these three error sources.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1990
- Accession Number
- ADA520297
Entities
People
- Christoph Thomas
- G. Petit
- M. A. Weiss
- W. Lewandowski
Organizations
- National Institute of Standards and Technology