Function epochPropErr( tYr, astrom22 )

Description:
Propagates the astrometry parameters and their associated errors and correlations, supplied as a 22-element array, to a different epoch.

The input and output astrometry parameters with associated error and correlation information are each represented by a 22-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 Declination
   5:   radial_velocity       km/s    barycentric radial velocity
   6:   ra_error              mas     error in right ascension
   7:   dec_error             mas     error in declination
   8:   parallax_error        mas     error in parallax
   9:   pmra_error            mas/yr  error in RA proper motion * cos(dec)
  10:   pmdec_error           mas/yr  error in Declination proper motion
  11:   radial_velocity_error km/s    error in barycentric radial velocity
  12:   ra_dec_corr                   correlation between ra and dec
  13:   ra_parallax_corr              correlation between ra and parallax
  14:   ra_pmra_corr                  correlation between ra and pmra
  15:   ra_pmdec_corr                 correlation between ra and pmdec
  16:   dec_parallax_corr             correlation between dec and parallax
  17:   dec_pmra_corr                 correlation between dec and pmra
  18:   dec_pmdec_corr                correlation between dec and pmdec
  19:   parallax_pmra_corr            correlation between parallax and pmra
  20:   parallax_pmdec_corr           correlation between parallax and pmdec
  21:   pmra_pmdec_corr               correlation between pmra and pmdec
 
Note the correlation coefficients, always in the range -1..1, are dimensionless.

This is clearly an unwieldy function to invoke, but if you are using it with the gaia_source catalogue itself, or other similar catalogues with the same column names and units, you can invoke it by just copying and pasting the example shown in this documentation.

This transformation is only applicable for radial velocities determined independently of the astrometry, such as those obtained with a spectrometer. It is not applicable for the back-transformation of data already propagated to another epoch.

Parameters:
tYr (floating point)
epoch difference in years
astrom22 (array of floating point)
astrometry at time t0, represented by a 22-element array as above
Return Value (array of floating point):
astrometry at time t0+tYr, represented by a 22-element array as above
Example:
epochPropErr(-15.5, array( ra,dec,parallax,pmra,pmdec,radial_velocity, ra_error,dec_error,parallax_error,pmra_error,pmdec_error,radial_velocity_error, ra_dec_corr,ra_parallax_corr,ra_pmra_corr,ra_pmdec_corr, dec_parallax_corr,dec_pmra_corr,dec_pmdec_corr, parallax_pmra_corr,parallax_pmdec_corr, pmra_pmdec_corr)) - calculates the astrometry with all errors and correlations at 2000.0 for gaia_source values that were observed at 2015.5.
Signature:
double[] epochPropErr(double, double[])