GRAPHIC DEPICTION OF DYNAMIC SATELLITE CONSTELLATION ACCURACY/COVERAGE OVER TIME

Barry A. Stein, Col. Eric Wheaton

Peer Reviewed

Abstract:	The Global Positioning System (NAVSTAR/GPS) should reach full 3D capability in mid-1990. The constellation is expected to consist of 18 basic satellites and three active spares deployed in six orbital planes. It has been shown that the proposed constellation yields occasional geometric configurations that result in poor navigation solutions, of importance to both the civilian and military aircraft communities. Analyses were undertaken to determine if placing the three active spares in an equatorial orbit at the same altitude as the other satellites would improve the situation. Upon comparing the currently envisioned constellation with the concept of equatorial sparing, it becomes clear that the major degradation areas that occurred along the 4O”N parallel no longer exist with equatorial sparing. Modelling also shows that even though a degradation can exist for 34-minutes, as an example, there is no geographic location in this region that is actually degraded with a GDOP > 6 for more than 9 minutes due to the dynamic changes in the size and shape of the degradation area. It is clear that for any given time the degraded area is smaller than previously indicated, and that for any given location the duration of the degradation is less than previously calculated.
Published in:	NAVIGATION: Journal of the Institute of Navigation, Volume 34, Number 3
Pages:	260 - 274
Cite this article:	Stein, Barry A., Wheaton, Col. Eric, "GRAPHIC DEPICTION OF DYNAMIC SATELLITE CONSTELLATION ACCURACY/COVERAGE OVER TIME", NAVIGATION: Journal of The Institute of Navigation, Vol. 34, No. 3, Fall 1987, pp. 260-274.
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