The CHIME/FRB Outriggers: Commissioning the Hat Creek Outrigger and an Updated Calibration Scheme for Mitigating RFI
Year: 2026
Type: preprint
Abstract: This work presents commissioning of the Hat Creek Outrigger (HCO), a dual-polarization 256-element radio interferometer that is part of the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst (CHIME/FRB) Outrigger project. Driven by a complex radio-frequency interference (RFI) environment that consistently contaminates $\sim40\%$ of HCO's usable bandwidth, we implement an improved calibration scheme using Gaussian Process Regression to recover complex gain solutions over RFI contaminated channels. To validate our method, we test the performance of the array using known transients and continuum sources over relevant timescales used for fast-transient research ($\lesssim$ seconds). We find that our updated calibration scheme results in a $\sim1.69\times~\mathrm{to}~1.87\times$ improvement in the array's point-source sensitivity, while simultaneously maintaining noise properties consistent with thermal statistics. As a result, we find that the array performs consistently within theoretical expectations across $\gtrsim80\%$ of HCO's bandpass. We further observe an improvement in the interferometric performance after applying recently developed spatial filtering techniques for RFI mitigation, which rely on accurate calibration solutions for effective removal of unwanted interference. We conclude that our approach provides a valid framework for improving calibration solutions over RFI contaminated channels for large-$N$ interferometric arrays more broadly. Our work motivates future development of more sophisticated techniques to recover astrophysical information in RFI-contaminated channels, departing from the historical practice of discarding them outright.
Source: arXiv (Cornell University)
Authors: Lazda, Mattias, Gusinskaia, Nina V., Sachdeva, Gurman, Andrew, Shion, Mena-Parra, Juan, Amiri, Mandana, Andersen, Bridget C., Atkinson, Alyssa, Bandura, Kevin, Curtin, Alice P., Dobbs, Matt, Hendricksen, Ian, Hessels, Jason W. T., Hewitt, Danté M., Kaspi, Victoria M., Khairy, Kholoud, Khan, Afrokk, Joseph, Ronniy C., Lanman, Adam E., Leung, Calvin, Masui, Kiyoshi W., Pearlman, Aaron B., Pollak, Alexander W., Shah, Vishwangi, Shin, Kaitlyn, Siegel, Seth R., Wang, Haochen, Zegmott, Tarik J
Institutions: University of Toronto, University of Amsterdam, Netherlands Institute for Radio Astronomy, Massachusetts Institute of Technology, University of British Columbia, West Virginia University, Trottier Space Institute at McGill, McGill University, University of California, Berkeley, Search for Extraterrestrial Intelligence
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, National Aeronautics and Space Administration, Gordon and Betty Moore Foundation, Adolph C. and Mary Sprague Miller Institute for Basic Research in Science, University of California Berkeley, Canadian Institute for Advanced Research, Canarie, McGill University, Space Telescope Science Institute, Government of Canada, European Commission, Universiteit van Amsterdam, Canada Excellence Research Chairs, Government of Canada, Nederlandse Organisatie voor Wetenschappelijk Onderzoek, University of Toronto, Alliance de recherche numérique du Canada, McGill Space Institute, Canadian Space Agency, Natural Sciences and Engineering Research Council of Canada, Fonds de recherche du Québec – Nature et technologies
Awards: Collaborative Research: Mapping the universe in neutral hydrogen with CHIME, G1908529863, G1979407794, G2614460161, Cutting-edge radio telescopes for cosmology and time-domain astrophysics, G433322167, G4850912966, G4998900716, G5169063652, G5180320897, G5433740808, G5539312340, G5622021303, G58316358, G6273510985, G7542343701
OpenAlex ID: W7212288402