Some of you may be interested in this: Upham, John. "An Orbit Propagator which Models Atmospheric Drag, J2 Effect, and Lunar Perturbations". November 1996. http://www.cris.com/~Uphamjk/Thesis/Thesis.shtml It's not clear whether this is a senior, master's or doctoral thesis, or none of the above. --Sue Worden (worden@uts.cc.utexas.edu)