astroforge.coordinates.PosVelConversion

astroforge.coordinates.PosVelConversion(conversion, mjd, X0, V0)

Utility for converting a cartesian position and velocity vectors from one coordinate system to another. The first argument should be the conversion method.

Parameters:

• conversion (Callable) – Method to call on the position and velocity vectors to do the conversion

• mjd (float) – Reference time for the conversion, specified as a Modified Julian Date (MJD) in the UT1 time system.

• X0 (NDArray[np.float64]) – Position vector to be rotated

• V0 (NDArray[np.float64]) – Velocity vector to be rotated

Returns:

X, V – Rotated position and velocity vectors

Return type:

Tuple[NDArray[np.float64], NDArray[np.float64]]

Examples

Rotate an ITRS site location (fixed relative to a rotating Earth) to pos/vel vectors in the True Equator True Equinox of Date (TETED) coordinate system:

>>> # pick a site location
>>> lat, lon, alt = 42.459629, -71.267319, 0.0
>>>
>>> # convert lat/lon/alt to an ITRS position vector
>>> x_itrs = LatLonAltToITRS(lat, lon, alt)
>>> v_itrs = np.array([0.0, 0.0, 0.0])  # site isn't moving in earth-fixed coordinates
>>>
>>> # time, used as a reference epoch for the TETED coordinate system
>>> mjd = 51720.0
>>>
>>> # do the conversion
>>> x_teted, v_teted = PosVelConversion(ITRSToTETED, mjd, x_itrs, v_itrs)
>>> with np.printoptions(suppress=True):
>>>     print(f"{x_teted = }")
>>>     print(f"{v_teted = }")
x_teted = array([-4364.24798307, -1778.39228689,  4283.414358  ])
v_teted = array([ 0.12968241, -0.31824598, -0.        ])