earthvelocity

sofia_redux.spectroscopy.earthvelocity.earthvelocity(ra, dec, time, equinox='J2000', frame='FK5', time_format=None, time_scale=None, lat=None, lon=None, height=0.0, center='heliocentric', definition='kinematic')[source]

Provide velocities of the Earth towards a celestial position.

The Local Standard of Rest allows for two different definitions defined by the definition keyword:

  • ‘kinematic’ uses 20 km/s towards 18:00:00, +30:00:00 (‘J1900’)

  • ‘dynamical’ uses the IAU definition of 9, 12, and 7 km/s along the x, y, and z axis in Galactic cartesian coordinates.

Parameters:
rastr or float or Angle or array_like

The right ascension[s] of the position[s]. Default unit is hourangle.

decstr or float or Angle or array_like

The declination[s] of the position[s]. Default unit is degrees.

timestr or float or Time or array_like

Time of the observation.

equinoxstr, optional

Coordinate frame equinox

framestr, optional

Type of coordinate frame represented.

time_formatstr, optional

Format of the input time. See astropy.time for available formats.

time_scalestr, optional

Time scale of time. See astropy.time for available scales.

latstr or float or Latitude or array_like, optional

The latitude of the observation. Default unit is degrees.

lonstr or float or Longitude or array_like, optional

The longitude of the observation. Default unit is degrees.

heightstr or float or Quantity, optional

The height of the observation. Default unit is meters.

centerstr, optional

Defines the center of the Solar System. One of {‘heliocentric’, ‘barycentric’}.

definitionstr, optional

Defines the Local Standard of Rest (LSR) definition as described above. One of {‘kinematic’, ‘dynamical’}.

Returns:
velocitiesdict

vhelio -> Velocity of the Earth wrt the Sun towards (ra, dec) ‘vsun’ -> Velocity of the Solar motion wrt LSR towards (ra, dec) ‘vlsr’ -> Net radial velocity of the Earth wrt LSR towards (ra, dec)

Note if arrays were passed in, then arrays will be passed out. However,
all values will be astropy.units.Unit.Quantity with units in km /s.