Since angular momentum is conserved, then Lp=La; if the orbit parameters a and e are known and the velocity at either the apogee or perigee point is known, then the velocity at the o...Since angular momentum is conserved, then Lp=La; if the orbit parameters a and e are known and the velocity at either the apogee or perigee point is known, then the velocity at the other point is known: One can change the spacecraft velocity at perigee to create a circular orbit whose radius is equal to the perigee distance, or one can change the spacecraft velocity at apogee to create a circular orbit whose radius is equal to the apogee distance.
