However, targeting in this manner limits the mission designer to changing the plane only along the line of apsides.

A straight line drawn through the periapsis and apoapsis is the line of apsides.

An apse line (or line of apsides) is an imaginary line defined by an orbit's eccentricity vector.

It also corresponds to the rotation of the Laplace-Runge-Lenz vector, which points along the line of apsides.

The following diagram shows the relation between the line of solstice and the line of apsides of Earth's elliptical orbit.

The next run, scheduled in ten minutes, would unite this African device with New Guinea in an effort to shift Beta's orbital line of apsides slightly.

Subsequent observations of the planetary orbits showed that the long axis of the ellipse (the so-called line of apsides) rotates gradually with time; this rotation is known as apsidal precession.

Nobody could ascertain the exact purpose of the set of maneuvers; they were just "orientation changes," according to the Earth scientists, that had altered the inclination and line of apsides of the Rama orbit.

To-day I became strongly impressed with the idea, that the balloon was now actually running up the line of apsides to the point of perigee- in other words, holding the direct course which would bring it immediately to the moon in that part of its orbit the nearest to the earth.