calc_scale_factor

romanisim.util.calc_scale_factor(date, ra, dec)

Calculate velocity aberration scale factor

The L2 orbit is just a delta on the Earth’s orbit. At the moment, there is no ephemeris for Roman yet, the Earth’s barycentric velocity is used to calculate velocity aberration. A scale of 1.01 is applied to the velocity to scale, approximately, to what would be Roman’s velocity.

Parameters:

datestr or astropy.Time

The date at which to calculate the velocity.

ra, dec: float

The right ascension and declination of the target (or some other point, such as the center of a detector) in the barycentric coordinate system. The equator and equinox should be the same as the coordinate system for the velocity. In degrees.

Returns:

scale_factorfloat

The velocity aberration scale factor