orbit_is_invertible

ell1fit.phase_utils.orbit_is_invertible(PB, A1, EPS1=0.0, EPS2=0.0)

Whether arrival time can be inverted for these orbital parameters.

The deorbiting iteration contracts only while |A1| * omega * (1 + |EPS1| + |EPS2|) < 1. That expression has a direct physical reading: A1 is in light-seconds and omega in radians per second, so A1 * omega is the projected orbital velocity in units of c. The condition is therefore simply that the pulsar’s projected motion is subluminal – with the eccentricity terms adding their contribution.

Beyond it the arrival-time map is not monotonic in emission time, so no inverse exists and no iteration scheme can find one. Real pulsars sit around 1e-3, many orders of magnitude inside the limit; a fit only reaches this region when an optimizer or sampler probes a wild trial position.

Returns:

bool

True when deorbiting is well posed.