WORLDWIDE COVERAGE OF THE PHASE II NAVSTAR SATELLITE CONSTELLATION

Wayne F. Brady and Paul S. Jorgensen

Peer Reviewed

Abstract:	The Navstar/Global Positioning System is now in Phase II, the Full Scale Engineering Development phase, which will extend into 1983. For the next few years, before the buildup to an operational 18-satellite constellation, four, five, or, possibly, six satellites will be maintained in orbit to support a variety of Phase II activities. This paper discusses the worldwide coverage that is provided by the Phase II constellation. Even with this limited number of satellites, much of the earth is afforded some coverage, though the period of coverage will vary from location to location. Certain locations are favored whereas others are not. A primary consideration in the design of this partial constellation was the need for engineering development tests of Navstar user equipment at the Army Proving Grounds in Yuma, Arizona. Four satellites provide 2 hr of three-dimensional navigation test time at this location once each day. Because the satellites assume the same relationship to each other four times each day, three other areas of the earth will be provided coverage similar to that at Yuma. Six hours after the test period at Yuma, a similar coverage pattern appears over the South Atlantic, then over the Middle East, and, finally, over New South Wales in Australia. Even at some distance from these favored locations, good coverage is provided (and has been exploited), although generally for a shorter period of time. Navstar has been successfully used as a range instrumentation system by the Navy in Atlantic Ocean tests designed to improve the accuracy of the Trident missile. During the Fall of 1980, there was a series of tests in Europe, also quite successful. Just as there are four most-favored areas on the earth, there are also four areas for which the coverage is poor. These four are over ocean areas and include the Canary Islands in the North Atlantic, the Mascarene Islands off Madagascar in the Indian Ocean, Wake Island in the North Pacific, and Easter Island in the South Pacific. This paper presents an overview of worldwide coverage, showing the variation between many locations on the earth. With only four or five satellites in the current development phase, Navstar is a part-time system that provides potential users a few hours of service each day. This could be useful for those users who are able to adjust their operations to when the satellites are visible or who wish to gain experience with Navstar prior to the buildup to the operational satellite constellation.
Published in:	NAVIGATION: Journal of the Institute of Navigation, Volume 28, Number 3
Pages:	167 - 177
Cite this article:	Brady, Wayne F., Jorgensen, Paul S., "WORLDWIDE COVERAGE OF THE PHASE II NAVSTAR SATELLITE CONSTELLATION", NAVIGATION: Journal of The Institute of Navigation, Vol. 28, No. 3, Fall 1981, pp. 167-177.
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