Dataset Open Access

Cygnus A 8.45 GHz interferometric observation with Allen Telescope Array


This dataset corresponds to an interferometric observation that was done in the context of the GNU Radio community activities at Allen Telescope Array. The observation was carried out using a GNU Radio FX software correlator and two USRP N32x SDR transceivers, as well as some custom code for phasing and data reduction.

Cygnus A and some compact sources (3C84, 3C286, J2007+404) were observed over three days between 2021-07-23 and 2021-07-25 using 6 antennas from the array. The observation frequency was 8.45 GHz. Two USRP N32x were connected to the 512 MHz IF output of the RFCB LO d. Each USRP digitized the two polarizations of one antenna. This setup requires baselines to be iterated one at a time for interferometric observing. The observing bandwidth was 40.96 MHz.

An FX correlator with 2048 channels and an integration time of 0.1 seconds was implemented in GNU Radio. The drifting correlations were then phased to each source in post processing. CASA was used for calibration and imaging.

This post contains the following files:

  • ATA-20210723.tar, ATA-20210724.tar, and ATA-20210725.tar contain the phased correlator output for each of the days in UVFITS format, reduced to a rate of 1 second and 64 channels
  • CASA-masks.tar contains CLEAN masks to be used with CASA and this script to reproduce the whole CASA pipeline starting from the UVFITS files
  • CASA-images.tar contains CLEAN images and self-calibrated CLEAN images for all of the sources in FITS format, as well as the ancialliary files produced by CASA during tclean

The raw FX correlator output is not included in this dataset because of size constraints.

More information about this observation and the processing pipeline can be found in the post "Imaging Cygnus A at 8.45 GHz with ATA" by the author.

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