Precise Ephemerides for GPS Time Transfer

Abstract

The present technology of atomic clocks motivates time transfer techniques with nanosecond accuracy. Global Positioning System (GPS), the most common means for international time comparisons could achieve such accuracy over short distances (up to 1000 km). Over intercontinental distances the accuracy of the GPS time transfer ranges between 20 and 30 ns. Some of the principal error sources are the broadcast ephemerides, the broadcast ionospheric model, and the local antenna coordinates. This study investigates the quality of broadcast ephemerides by comparing them with precise ephemerides and by using precise ephemerides for time transfer. Another aspect of this work is to suggest a strategy to overcome the planned degradation of GPS satellite messages via Selective Availability (SA).

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Document Details

Document Type
Technical Report
Publication Date
Nov 01, 1989
Accession Number
ADA504950

Entities

People

  • M. A. Weiss
  • W. Lewandowski

Organizations

  • National Institute of Standards and Technology

Tags

DTIC Thesaurus Topics

  • Accuracy
  • Artificial Satellites
  • Availability
  • Clocks
  • Communities
  • Coordinate Systems
  • Degradation
  • Ephemerides
  • Geodetic Surveys
  • Global Positioning Systems
  • Measurement
  • Oceans
  • Orbits
  • Spacecraft
  • Standards
  • United States
  • World Geodetic System

Readers

  • Computational Modeling and Simulation
  • Positioning, Navigation, and Timing (PNT) Technology.

Technology Areas

  • Space
  • Space - Orbital Debris