  Phased formations of satellites provide an important means of keeping
multiple satellites in close proximity without becoming dangerously close to
one another. In order to minimize the amount of propellant necessary to keep a
set of satellites in a phased formation, this paper presents a new condition
for in-plane linearized secular J2-invariance in highly eccentric orbits. A
maintenance strategy outlined here combats the growth of out-of-plane motion,
and the delta-v cost of this strategy is analyzed. For context, this paper also
discusses relevant formations that benefit from this condition and maintenance
strategy. A highly elliptical perching formation called the boomerang perch is
also discussed.
