WIDG Seminar: Emily Kuhn, Yale, “Calibration Instrumentation for the Hydrogen Intensity and Real-time Analysis eXperiment”

The Hydrogen Intensity Real-time Analysis eXperiment (HIRAX) is a 21cm radio telescope array to be deployed in South Africa. It will consist of 1024 six meter parabolic dishes, and will map much of the southern sky over the course of four years. HIRAX is designed to improve constraints on the dark energy equation of state through measurements of large scale structure at high redshift, and will additionally monitor transients such as fast radio bursts (FRBs) and pulars, as is currently done with CHIME in the Northern Hemisphere. The southern location will also allow for a variety of cross-correlation measurements with other cosmology surveys such as ACTPol, DES, and the Vera Rubin Observatory. Currently, an 8-element prototype array has been deployed at Hartebeesthoek Radio Astronomy Observatory (HartRAO) in South Africa, and a 256-element array is being developed at the final HIRAX site.
As with all 21cm science, galactic foregrounds contaminate our frequency band, and so meeting the HIRAX science goals will require precise haracterization of the instrument. In addition to an overview of HIRAX, this talk will focus on two key aspects of the HIRAX instrument characterization: (1) antenna noise temperature assessment, and (2) telescope beam measurements. For the first, I will discuss an apparatus for determining antenna noise temperature, involving a custom cryogenic system capable of containing >550L of liquid nitrogen. This apparatus has been constructed at Yale, and over the course of the past year has undergone detailed verification tests and preliminary data taking, providing the first noise temperature measurements of the HIRAX feed, and the first analysis of feed repeatability. For the second, I will describe how to use drone systems for telescope calibration, report results from flights over two different radio telescopes, and touch on a local testbed built at Yale for testing hardware upgrades. For both projects, I will report updates and results, from data over the past year, as well as ongoing challenges and next steps.
Host: Giacomo Scanavini