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SourceSys - Spectral system in which the source velocity is stored

Description:
This attribute identifies the spectral system in which the SourceVel attribute value (the source velocity) is supplied and returned. It can be one of the following:

  • "VRAD" or "VRADIO": Radio velocity (km/s)

  • "VOPT" or "VOPTICAL": Optical velocity (km/s)

  • "ZOPT" or "REDSHIFT": Redshift (dimensionless)

  • "BETA": Beta factor (dimensionless)

  • "VELO" or "VREL": Apparent radial ("relativistic") velocity (km/s)

When setting a new value for the SourceVel attribute, the source velocity should be supplied in the spectral system indicated by this attribute. Likewise, when getting the value of the SourceVel attribute, the velocity will be returned in this spectral system.

If the value of SourceSys is changed, the value stored for SourceVel will be converted from the old to the new spectral systems.

The default value is "VELO" (apparent radial velocity).

Type:
String.
Class Applicability:
SpecFrame
All SpecFrames have this attribute.


next up previous 264
Next: SourceVRF - Rest frame in which the source velocity is stored
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AST A Library for Handling World Coordinate Systems in Astronomy
Starlink User Note 211
R.F. Warren-Smith & D.S. Berry
7th December 2012
E-mail:starlink@jiscmail.ac.uk

Copyright (C) 2012 Science \& Technology Facilities Council