Introduction

All GBT scan data GO FITS files should conform to the standards specified in the GBT Software Project Note 4.0, ``Device and Log FITS Files for the GBT.'' In version 1.1 the GO FITS files consist simply of ASCII header records, with no associated data, and no extensions. The information in the header records can be split into five main categories, as follows:

• GBT standard primary header keywords,
• additional ``housekeeping'' related keywords
• Observing procedure related keywords,
• Target positional information, and
• Target frequency related information.

These are described in detail in the following sections.

The GO FITS files are slightly unusual in that they are produced by calls to a glish procedure and corresponding glish client, rather than a C++ device manager. However, apart from some subtleties in the GBT standard header keywords, this has no other impact on the structure or content of the files.

NOTE: At the time of production of FITSVER 1.2 GO FITS files, the file can only be expected to be complete if the observer configures the system and executes scans using GBT supplied glish procedures and observing tables. Although it is entirely legitimate for an observer to configure the system using their own private procedures, we have not yet devised a mechanism to reliably ensure that these will write all the required information to the GO FITS file.