Light travel time correction to the barycentre or heliocentre.

The frame transformations used to calculate the location of the solar system barycentre and the heliocentre rely on the erfa routine epv00, which is consistent with the JPL DE405 ephemeris to an accuracy of 11.2 km, corresponding to a light travel time of 4 microseconds.

The routine assumes the source(s) are at large distance, i.e., neglects finite-distance effects.

Parameters¶

skycoord~astropy.coordinates.SkyCoord

The sky location to calculate the correction for.

kindstr, optional

'barycentric' (default) or 'heliocentric'

location~astropy.coordinates.EarthLocation, optional

The location of the observatory to calculate the correction for. If no location is given, the location attribute of the Time object is used

ephemerisstr, optional

Solar system ephemeris to use (e.g., ‘builtin’, ‘jpl’). By default, use the one set with astropy.coordinates.solar_system_ephemeris.set. For more information, see ~astropy.coordinates.solar_system_ephemeris.

Returns¶

time_offset~astropy.time.TimeDelta

The time offset between the barycentre or Heliocentre and Earth, in TDB seconds. Should be added to the original time to get the time in the Solar system barycentre or the Heliocentre. Also, the time conversion to BJD will then include the relativistic correction as well.