make_param_guess
- ssapy.correlate_tracks.make_param_guess(rvguess, arc, mode='rv', orbitattr=None)[source][source]
Generates an initial parameter guess for orbital estimation based on the provided mode, observation arc, and optional orbital attributes.
Parameters:
- rvguesslist or array-like
Initial guess for the state vector (position and velocity). Typically contains six elements: [x, y, z, vx, vy, vz].
- arcstructured array
Observation arc containing time and station data. Must include: - ‘time’: Observation times (assumed to have a .gps attribute). - ‘rStation_GCRF’ and ‘vStation_GCRF’: Position and velocity of the station in the GCRF frame. - ‘pmra’ (optional): Proper motion in right ascension (used to determine if proper motion data is available).
- modestr, optional
The mode for parameter generation. Must be one of: - ‘rv’: Radial velocity mode (default). - ‘equinoctial’: Equinoctial orbital elements mode. - ‘angle’: Angular observation mode.
- orbitattrlist of str, optional
Additional orbital attributes to include in the parameter guess. Supported attributes include: - ‘mass’: Mass of the object. - ‘area’: Cross-sectional area. - ‘cr’: Radiation pressure coefficient. - ‘cd’: Drag coefficient. - ‘log10area’: Logarithm of the cross-sectional area.
Returns:
- list
A list of guessed parameters based on the specified mode: - For ‘rv’: [rvguess, extraparam, epoch]. - For ‘equinoctial’: [equinoctialElements, extraparam, epoch]. - For ‘angle’: [radecrate, extraparam, epoch, initObsPos, initObsVel].
Raises:
- ValueError
If an unrecognized mode is provided.
Notes:
The epoch is determined based on the observation times in the arc. If proper motion data (‘pmra’) is available, the epoch is set to the first observation time. Otherwise, it is calculated as the midpoint between the first two observation times.
For ‘equinoctial’ mode, the initial state vector (rvguess) is converted into equinoctial orbital elements using the Orbit class from ssapy.
For ‘angle’ mode, the initial observation position and velocity are computed based on the station’s GCRF data. If proper motion data is available, only the first observation is used; otherwise, the average of the first two observations is used.