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Registered FITS Convention
Single Dish FITS (SDFITS) Convention for Radio Astronomy Data
- Description: The SDFITS binary table convention is used for interchange of single dish data in radio astronomy
- Submitted: August 2010 by Robert Garwood (NRAO) and Mark Calabretta (ATNF/CSIRO)
- Registered: August 2012
- Date and Place of First Usage: SDFITS was developed at a meeting of representatives from many major radio astronomy observatories at Green Bank, West Virginia in October 1989.
- Extent of Usage: Variants of the SDFITS convention are used by a number of radio observatories, including NRAO, Arecibo, Parkes, and Mopra (Australia). The definition document (below) specifically applies to the NRAO version of SDFITS; the data from other observatories may differ slightly.
- Full Documentation:
- SDFITS definition document: PDF format, Postscript format
- see also Garwood (2000)
- Comments and/or critiques:
- Discussion of differences between the NOAO and Parkes SDFITS formats: sdfits_format.txt
- Sample FITS Files:
- PParkes_GASS.fits This file is from the Parkes Galactic All Sky Survey (GASS) of the atomic hydrogen (HI) emission in the southern Milky Way. It contains 7-beam, 2 polarization x 2049 channel, 8MHz bandwidth, dual-IF, scanned, frequency-switched Parkes multibeam GASS data. The data table has been truncated to 28 rows to reduce the size of the file. This file differs from the SDFITS documentation in having a vector TSYS column, with one value for each polarization.
- TREG_091209.cal.acs.fits, This file contains processed (by GBTIDL) Green Bank Telescope (GBT) data.
Additional comments from Bob Garwood:This shows how we add a new extension when the data length changes. I don't believe it differs from the convention. For the GBT we always write one spectrum per row. I went that route rather than how I approached things for the aips++ sdfits writer (which is what Mark's example is closer to - i.e. both polarizations on the same row) after a conversation with Harvey about 6-7 years ago where he said that it was his impression that the sdfits convention was never meant to hold more than one spectrum per row because of the scalar nature of the TSYS column.I've used fv on this example file to pare it down from it's original size of 30 rows in the first extension and 300 rows in the second extension to something more manageable. The first extension is calibrated individual integrations from an observation of a galaxy. There's 2 polarizations and one spectral window. The raw data is position switched data. The second extension is 2 polarizations and 2 spectral windows of a different galaxy. It's also calibrated individual integrations and the raw data were 2-beam nodding data (one scan with one beam on source followed by a second scan with the other beam being on source) - it's shorter integrations so the emission is harder to see in the individual integrations than it is for the data in the other extension.
- Sample Header Listings:
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