MBFITS - Multi-Beam FITS Raw Data Format

In addition to the hardware interfaces, one also needs to define the data product interfaces. There was a lack of modern single dish raw data data format descriptions when the APECS developments began. We therefore defined a new data format called Multi-Beam FITS / MBFITS to store the raw APEX data.

The MBFITS format was derived structurally from the ALMA Test Interferometer FITS (ALMA-TI FITS) raw data format, although a number of changes had to be made to accommodate the special needs of the APEX and also the IRAM 30m and Effelsberg 100m telescopes where MBFITS is being used.

The MBFITS format uses the FITS standard and the World Coordinate System (WCS) representation. MBFITS is based on the scan-subscan-integration scheme used by ALMA-TI FITS and retains many of its keywords. However, due to the changes in structure and additional keywords needed to accommodate modern single-dish configurations, particularly multiple beam observing and multiple frontend/backend combinations, the MBFITS format can now be considered to be an independent format.

In 2007 the MBFITS format has been added to the Registry of FITS Conventions maintained by the IAU FITS Working Group (https://fits.gsfc.nasa.gov/registry/mbfits.html). MBFITS is now also being used by further observatories such as the Yebes 40m and Sardinia 64m radio telescopes.

Design

For each level of time granularity (scan, subscan, backend integration) there are FITS binary tables to store the corresponding data. A special flexible format monitoring table allows recording important instrument parameters in parallel to the backend data stream for later analysis.

References

Greisen, E.W. & Calabretta, M.R., 2002 Representations of world coordinates in FITS, A&A, 395, 1061-1075
Lucas, R. and Glendenning, B., 2001, ALMA Test Interferometer Raw Data Format, ALMA Report ALMA-SW-0015.
Muders, D., Polehampton, E. & Hatchell, J., 2018, Multi-beam FITS Raw Data Format, APEX Report APEX-MPI-IFD-0002, Rev. 1.67 [pdf]
Registry of FITS Conventions, https://fits.gsfc.nasa.gov/registry/mbfits.html
Wells, D.C., Greisen, E.W. & Harten, R.H., 1981, FITS - a Flexible Image Transport System, A&AS, 44, 363-+