Robert C. Byrd Green Bank Telescope

NRAO Green Bank

Garwood and Roshi

December 11, 2017
GBT Software Project Note 33.2

GBT VEGAS FITS File Specification

PDF Version

Abstract:

The FITS format structure is presented for the GBT VEGAS scan data files. The scan data FITS files are permanently archived after each observation, and will usually be input to a GBT filler, which has the task of combining all scan data FITS files into some other form (e.g. SDFITS). This data may then be processed further in an analysis package (e.g. GBTIDL).

The scan data FITS files contain both 1) a complete description of the VEGAS setup for the observation and 2) measurement data with a FITS keyword description of the data organization. The ACT_STATE, PORT, STATE and SAMPLER tables describe the setup and the DATA table contains measured data values (spectra). The SPURStable contains a list of known channels affected by ADC spurs.

History

11 July 2011

Initial draft (Bob Garwood).

21 July 2011

Draft ready for wider comment (Bob Garwood).

12 April 2012

Verion 1.0 is set by this document. VEGAS FITS files produced on this date have been verified to agree with this document (Bob Garwood).

23 August 2013

Updated to include changes during initial commissioning. Future changes will be accompanied by a change to FITSVER. In the PHDU, BOFFILE keyword noted, presence of VEGAS status keywords noted. In the DATA table, the un-normalized state of the DATA column was noted and 5 additional columns were documented. A more recent VEGAS FITS file was used as the source of the examples shown here. (Bob Garwood)

11 December 2017

Version 1.2. Added a table of known channels where ADC spurs are predicted for each IF listed in the SAMPLER table. Added descriptions of additional PRIMARY header keywords. Revised the note about normalization of data values.