Since angular momentum is conserved, then \(L_{p}=L_{a}\); 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 \(L_{p}=L_{a}\); 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.
