This parameter has to be used together with the
ReleaseRadius parameter. They both are relative to planet 0 only, and they can be used to specify a forced migration (with constant, arbitrary

). The planet 0 trajectory is forced for

ReleaseDate, and is such that at

ReleaseDate, the planet semi-major axis is equal to
ReleaseRadius. At

, the planet semi-major axis is the one indicated in the planet configuration file (see
PlanetConfig). Between

and

ReleaseDate, the semi-major axis of planet 0 is an affine function of time. Its angular speed is the Keplerian one corresponding to its instantaneous semi-major axis. For

ReleaseDate, the planet migrates according to the torque exerted by the disk (its orbit is no longer forced).