Novel Techniques for Creating Nearly Uniform Star Catalog

In order to develop optimize star sensing and star identification with respect to continues operation and reliability, the concept of star catalogs with near uniform angular spacing between stars arises. Such catalogs are not characterized by the usual constant magnitude cutoffs. With a uniform star catalog we want to build a reference star catalog where the expectation of the number of stars that fall in a given field of view is about constant (i.e. 5 or 6) with a minimized standard deviation, independently which region of the sky the sensor optical axis is pointing. This paper compares three different techniques to create uniform star catalogs. These methods mainly depend on creating a uniform distribution of points on the surface of a unit sphere. In particular, the first method divides the unit sphere into a large number of Spherical Patches all having the same area. The second method, which is derived from a mechanical analogy (and supported by consistent results with the known solution cases), considers uniform the equilibrium distribution of charged particle on the unit sphere. Finally, the third method creates a fixed slope Spiral over the unit sphere and then divide it into segments of the same length, that is, of identical areas. Once the uniform point distribution is created, then an approximated uniform star catalog is created for each set of N reference vectors by picks the cataloged star nearest each reference vector, that is brighter than some maximum cutoff magnitude. The tradeoffs between these approaches are studied by evaluation the inter-star angle statistics. Post-Doc Research Associate, Spacecraft Technology Center, Room 127H, Texas A&M University, College Station, TX 77843-3141, Tel. (979) 845-8768, samaan@tamu.edu Ph.D. Student, Department of Aerospace Engineering, Texas A&M University, College Station, TX 77843-3141, Tel. (979) 458-0550, bruccoleri@tamu.edu Associate Professor, Department of Aerospace Engineering, Texas A&M University, 3141 TAMU, College Station, Texas 77843-3141 Tel. (979) 845-0734, FAX (979) 845-6051. George J. Eppright Chair Professor, Department of Aerospace Engineering, Texas A&M University, College Station, TX 77843-3141, Tel: (979) 845-3912, Fax: (979) 845-6051, junkins@tamu.edu