Function astromUVW( astrom6 )

Description:
Calculates Cartesian components of velocity from quantities available in the Gaia source catalogue. The output is in the same coordinate system as the inputs, that is ICRS for the correspondingly-named Gaia quantities.

The input astrometry parameters are represented by a 6-element array, with the following elements:

 index  gaia_source name  unit    description
 -----  ----------------  ----    -----------
   0:   ra                deg     right ascension
   1:   dec               deg     declination
   2:   parallax          mas     parallax
   3:   pmra              mas/yr  proper motion in ra * cos(dec)
   4:   pmdec             mas/yr  proper motion in dec
   5:   radial_velocity   km/s    barycentric radial velocity
 
The units used by this function are the units used in the gaia_source table.

This convenience function just invokes the 7-argument astromUVW function using the inverted parallax for the radial distance, and without invoking the Doppler correction. It is exactly equivalent to:

    astromUVW(a[0], a[1], a[3], a[4], a[5], 1000./a[2], false)
 
Note this naive inversion of parallax to estimate distance is not in general reliable for parallaxes with non-negligable errors.
Parameters:
astrom6 (array of floating point)
vector of 6 astrometric parameters as provided by the Gaia source catalogue
Return Value (array of floating point):
3-element vector giving equatorial velocity components in km/s
Examples:
Signature:
double[] astromUVW(double[])