fit_arc

ssapy.correlate_tracks.fit_arc(arc, guess, verbose=False, propagator=KeplerianPropagator(), mode='rv', priors=None, damp=-1, optimizerkw={}, lsq=True, orbitattr=None, **kw)[source][source]

Fit an orbit to an arc.

See documentation for fit_arc_blind. fit_arc implements the same interface, but takes a additional guess & epoch arguments. These specify the initial guess in appropriate units given the chosen mode. epoch specifies the time at which this initial guess applies.

Parameters:

  • arc (array_like (n)) – numpy ndarray containing several fields necessary for describing observations. rStation_GCRF (m), vStation_GCRF (m), time (astropy.time.Time or gps seconds), ra, dec, pmra, pmdec are all required fields.

  • guess (array_like (n_par)) – parameters for initial guess guess[nparam] should be the epoch in GPS guess[nparam:] should be extra parameters not optimized over

  • verbose (bool) – True for more verbose output

  • propagator (ssapy.propagator.Propagator instance) – propagator to use in fitting

  • mode (str) – Mode for fitting, must be one of ‘rv’, ‘equinoctial’, or ‘angle’. In the first case, the parameters defining the orbit are taken to be the position and velocity of the object. In the second case, the parameters are taken to be the equinoctial elements. In the third case, the parameters are taken to be the angular position and proper motion of the object, together with its line-of-sight range and velocity.

  • priors (list of objects implementing ssa Prior interface) – any priors to be applied in fitting

  • damp (float) – Damping used in pseudo-Huber loss function. Default of -1 means no damping.

  • orbitattr (list(str)) – Names of orbit attributes used for propagation (mass, area, …)

  • optimizerkw (dict) – any extra keywords to pass to the optimizer

  • **kw (dict) – any extra keywords to pass to optimizer.optimize()