1. The problem statement, all variables and given/known data 2. Relevant equations g=GMm/r^2 e=c/a g=v^2/r 3. The attempt at a solution a) v^2/r=GM/r^2 m<<M v^2=GM/r v=SGRT(GM/r) I don't think this is valid though since the orbit is not circular. I don't know how to alter the equation so it also applies to the elliptical orbit of the problem. Thanks so much for any help.