The international GPS service (IGS): An interdisciplinary service in support of earth sciences

Since 21 June 1992 the International GPS Service (IGS) produces and makes available uninterrupted time series of its products, in particular GPS observations from the IGS Global Network, GPS orbits, Earth orientation parameters (components x and y of polar motion, length of day), satellite and receiver clock information, and station coordinates and velocities. At a later stage the IGS started exploiting its network for atmosphere monitoring, in particular far ionosphere mapping and for troposphere monitoring. This is why new IGS products encompass ionosphere maps and tropospheric zenith delays, both with a very high temporal resolution. This development will be even more pronounced through the advent of many space-missions carrying GPS, or combined GPS/GLONASS receivers for Various purposes. The achievements of the IGS are only possible through a unique voluntary cooperation of a great number of active organizations. This article gives an informative overview for the broader scientific community of the spectrum of problems that is addressed today using IGS/GPS techniques. (C) 1999 COSPAR. Published by Elsevier Science Ltd.