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Change GO fits file so that RA is in degrees

• 1. Introduction
• 2. Background
• 3. Design
• 4. Deployment Checklist
• 5. Test plan
• Signatures
• CCC Discussion Area

1. Introduction

GO Fits files should always write coordinates in degrees.

2. Background

The FITS standard has all coordinates (RA, Dec, Glong, etc) in degrees. In the past, GO wrote GO fits files with its coordinates in degrees. However, a request was made in July, 2004 to change the GO FITS files as written by astrid so that the RA-like coordinate is in whatever units were requested by the observer (e.g. hours). As this breaks both past behavior and with FITS convention, we need to revert to having the GO fits files always write the coordinates in degrees.

3. Design

The code added in July, 2004 will be removed so that all future GO fits files will write units in degrees. The version number of the GO fits file (FITSVER) will be updated to version 2.6 (it is 2.5 as of 24 Oct 2005). As sdfits does not use this keyword, there should be no impact on it.

The aips++ filler has already been modified to deal correctly with this change and to correctly process existing GO FITS files. The sdfits filler does not yet use this field and so no changes are necessary to existing code in sparrow.

4. Deployment Checklist

• Place description of change in release notes and notify affected observers of the bug and its resolution. The release notes should clearly state that non-NRAO fillers that use this field will need to be modified.
• Update http://www.gb.nrao.edu/GBT/MC/doc/dataproc/gbtGOFits/gbtGOFits/gbtGOFits.html with changes.
  • Software Project Notes can be found here: /home/gbt1/doc/dataproc/
  • These are the docs that correspond to the links at: http://www.gb.nrao.edu/GBT/MC/doc/index/spn_doc_index/
  • These are linked off off the DashBoard under Ygor (fifth link down).

5. Test plan

We will take some data with RA coordinates in hours and insure that what is recorded in the GO fits and sdfits files are correct. This can be done with the antenna simulator.

Test data should also be taken in any other coordinate system to ensure that those values are unchanged (still in degrees).

Verify that the aips++ filler does correctly fill this position in the MeasurementSet? for existing GO fits files (RA in hours) and for new GO fits files (RA in degrees).

Signatures

APPROVED: I acknowledge that my request is fully contained in this MR, and if the SDD delivers exactly what I specified, I will be happy.

ACCEPTED: I acknowledge that I have validated the completed code according to the acceptance tests, and I am happy with the results.

Written	- KarenONeil - 19 Oct 2005
Checked	- AmyShelton - 19 Oct 2005
Approved by Sponsor	- AmyShelton - 02 Nov 2006
Approved by CCC	- AmyShelton - 01 Dec 2006
Accepted/Delivered by Sponsor	- AmyShelton - 25 Jan 2007

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CCC Discussion Area