AAS 95-340

Refinement of a Sun-Synchronous, Critically Inclined Orbit for a Global Personal Communications System

J. Draim, Constellation Design, Mobile Communications Holdings, Inc., C. Sabol, Phillips Laboratory,Kirtland AFB, NM., P. J. Cefola, Draper Lab. , Cambridge, MA

Abstract

A sun-synchronous, critically inclined orbit with mean motion of eight revs per day was studied by the authors for use in the EllipsoTM Big-LEO personal communications system. The original version experienced moderately high atmospheric drag near the 520 km perigee; further, the one day repeat cycle caused significant Tesseral resonance. A convenient strategy for reducing these adverse effects has been found: (1) Tesseral effects are alleviated by increasing the repeat cycle from one day (with eight orbits) to ten days (with eighty-one orbits) and (2) Eccentricity and semi-major axis adjustments to maintain sun-synchronism also raise the perigee and thus reduce drag. The new, optimized, orbit reduces the maneuvering fuel required; the time interval between corrective maneuvers is increased.