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Robert C. Byrd Green Bank Telescope

NRAO Green Bank

Langston, Garwood, Prestage, Clark, Shelton and Hunt

March 8th, 2007
GBT Software Project Note 5.5

GBT Spectrometer FITS File Specification

PDF Version


The FITS format structure is presented for the GBT spectrometer scan data files. The scan data FITS files are permanently archived after each observation, and will usually be input to the aips++ filler, which has the task of combining all scan data FITS files into an aips++ Measurement Set. This data may then either be processed further in aips++, or written out in an aips++ supported FITS format (one of which is single dish FITS).

The scan data FITS files contain both 1) a complete description of the spectrometer 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 values.


8th November 2001
Penultimate definition of FITSVER 1.1; released for general comment (Richard Prestage).
16th November 2001
Final version agreed for implementation of FITSVER 1.1. No changes c.f. 8th November 2001 version. Subsequent changes to the content of this document should increment the document version number (Richard Prestage).
28th November 2001
Revised comment in PHDU section for DATE-OBS,
14th March 2002
Corrected description of ACT_STATE table (Mark Clark).
27th June 2002
Modifications for FITSVER 1.2. The polarity of the active switching signals in the ACT_STATE were reversed in previous versions (Mark Clark). OBJECT, PROJID, OBSID, and SCAN (Amy Shelton).
8th March 2007
Bug fix for FITSVER 2.3. The INTEGRAT column in DATA was being incorrectly written in column-dominant fashion when it should have been written in row-dominant fashion (John Ford, Melinda Mello, Mark Clark).

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Bob Garwood