Satellite Clusters with Constant Apparent Distribution

Theproblemofcreatingaclusterofsatellitessuchthatthearrangementmaintainsitsapparentrelativeformation as viewed from the planetary surface, without active station keeping, is considered. It is shown that it is possible to create a cluster with nearly constant circular form, but that rotates about its center. The amount of variation from the perfect circle is characterized in terms of the eccentricity of the satellite orbits. Because of the nature of the cluster, it is possible to put a large number of satellites into a cluster, with no danger of satellite collisions. An illustrative example is included. I. Introduction T HE work begun in this paper was motivated by the problem of creating a cluster of satellites that would maintain a constant, or nearly constant, shape and size when viewed from the Earth. Such a cluster might be said to have constant apparent (as opposed to physical) distribution. In such a formation, all satellites would have a clear e eld of view of the surface, and would remain in sufe ciently close formation to share their information. Such formations are of interest for large distributed-aperture sensing, for example. Another possibility is that of forming clusters from many small, inexpensive satellites, each with a particular type of sensor and some computing power. Remaining in a close formation would allow the satellites to share information and computing ability among themselves. Forsuch missions,it mightbe unnecessary tomaintain extremely precise relative positions; rather, it might be sufe cient to know the relative position accurately, and to remain in close enough proximity to allow intercraft communication. In addition, an effect of constant apparent distribution is that the angular dispositions of the satellites relative to their ground targets and each other would be