a = (q+Q)/2 = q+c = Semimajor Axis
q = a(1-e) = a-c = Periapsis Distance
Q = a(1+e) = a+c = Apoapsis Distance
e = c/a = 1-q/a = Q/a-1 = Eccentricity
i = Inclination
= Longitude of Ascending Node
= Argument of Periapsis