“…Since we are assuming a spherical Earth gravity model, during a coast phase the only equinoctial element that changes with time is the true longitude, L. In particular, during a coast phase the differential equation for the true longitude can be written as (4) Observing that all quantities except L in equation (4) are constant, we can separate variables in equation (4) to give (5) Integrating both sides of equation (5), we obtain (6) where are the initial and terminal time, respectively, of the coast phase while are the initial and terminal true longitude. Since all other states are constant during a coast phase (again, because we have assumed…”