REFINEMENT OF A SUN-SYNCHRONOUS, CRITICALLY INCLINED ORBIT FOR THE ELLIPSO(TM) PERSONAL COMMUNICATION-SYSTEM

This paper refines a sun-synchronous, critically inclined orbit with a pplication to the ELLIPSO(TM) global personal communications system. P revious work has shown this class of orbit to be maintainable in the p resence of long-term perturbations. The original versions of the orbit did, however, experience significant atmospheric drag and tesseral re sonance effects (due to the eight revolution per nodal day repeat grou nd track cycle). A convenient strategy for reducing these adverse effe cts has been found: (1) tesseral effects are alleviated by increasing the repeat cycle from one day (with eight orbits) to ten days (with ei ghty-one orbits) and (2) eccentricity and semi-major axis adjustments to maintain sun-synchronism also raise the perigee and thus reduce dra g. However, the application of the ELLIPSO Borealis(TM) constellation requires the orbital planes studied in the previous work to be rotated by 90 degrees in longitude of ascending node. This introduces signifi cant solar radiation pressure effects which must be countered in the s tationkeeping process. The new orbits still reduce the maneuvering fue l required while the coverage implications of the refined orbits are m inimal.