BIGCAT is the new Broadband Integrated GPU Correlator for ATCA, which has replaced the CABB (Compact Array Broadband Backend) with a hybrid FPGA+GPU backend. BIGCAT is doubling ATCA’s instantaneous bandwidth from 4 to 8 GHz (in bands above the 16cm band, where 2 GHz of bandwidth is available), will provide a spectral resolution of at least 0.6 kHz, and will significantly improve the reliability of the ATCA correlator. 

BIGCAT documentation

Documentation for BIGCAT is currently being updated.

The ATCA Users Guide remains useful in most aspects of the ATCA capabilities and usage, but the sections related to CABB are no longer relevant. The Guide is currently being updated. In the meantime, you may find the following useful:

• Version 4.0 (June 2026) of the BIGCAT Scheduler User Guide is now available.
• Version 3.2 (June 2026) of the Quick Start Guide to BIGCAT is also available.
• Instructions on accessing your data are now available. Observatory staff are currently handling the conversion step from ASDM to Measurement Sets (MS).
• A guide to BIGCAT Data Reduction in CASA is now available.
• A BIGCAT Change Log is being maintained as shared-risk observing progresses.

If you encounter any issues or bugs, please use the PORTAL and/or chat to your project OE (Observing Expert)

BIGCAT overview

BIGCAT is the Broadband Integrated GPU Correlator for ATCA, a project funded in part by an Australian Research Council Linkage Infrastructure, Equipment and Facilities (LIEF) grant. The LIEF funding is being led by Western Sydney University, working closely with CSIRO and seven other university partners. Ray Norris has written an article for The Conversation on the ATCA upgrade, reviewing some of the ATCA’s achievements to date, and outlining what the upgrade will enable.

The BIGCAT project will see the replacement of the CABB (Compact Array Broadband Backend) digitisers and correlator with a hybrid FPGA+GPU backend. BIGCAT will double the instantaneous bandwidth from 4 to 8 GHz (in bands above the 16cm band, where 2 GHz of bandwidth is available), provide a spectral resolution of at least 0.6 kHz, and significantly improve the reliability of the ATCA correlator.  BIGCAT will also provide more flexibility, with many more options for frequency resolution and integration times, the ability to change quickly between different correlator modes, and more adaptable to rapid-response observing. BIGCAT will retain standard CABB features such as mosaicing.

BIGCAT will come with a new version of the ATCA observing program caobs, a new scheduling tool, a new file format (replacing RPFITS with ASDM), and a new archive (moving from ATOA to CASDA). The ASDM (ALMA Science Data Model) data format is a Measurement Set (MS) filesystem which is natively compatible with CASA. Users will be able to use CASA for data processing and analysis, or export to FITS format to be reduced using miriad. Further information and training for observers will be provided as BIGCAT implementation and commissioning progresses.

The first phase of BIGCAT, replacing the correlator, was installed during the 2025APR semester and will be offered in a shared-risk observing mode after a period of commissioning and verification. Scientific commissioning of BIGCAT is currently (August 2025) underway. BIGCAT will initially support the same observing modes as currently offered by CABB and will be limited to the existing IF setup of 2×2 GHz. Proposers requesting ATCA observations in this semester should prepare observations tables using the current CABB configuration with any technical requirements not captured in the observations table clearly stated in the proposal text. It is anticipated that additional BIGCAT observing modes, including pulsar binning mode and increased bandwidth of 4×2 GHz, will be made available during 2025OCT.

Further information is available from this presentation to ATUC in April 2024, and updates in the ATNF Daily Astronomy Picture.