Observations of redshifted 21-cm emission of neutral hydrogen are a rapidly growing area of cosmology research. Measurements of the radio sky at ~200 MHz and below are a promising tool for exploring cosmic dawn, and at the lowest frequencies (tens of MHz), future observations may allow us to one day probe the dark ages. However, observations at these low frequencies are challenging because of Galactic foreground contamination, ionospheric effects, radio-frequency interference, and instrumental systematics. I will discuss the current status of cosmic dawn measurements from ground-based global 21-cm experiments, and I will introduce two projects, MIST and PRIZM. I will also describe ALBATROS, a companion experiment that is designed to image the low-frequency sky using an array of autonomous antenna stations. With the combination of instrumentation advances and new radio-quiet sites, these experiments aim to open observational windows into the early history of our universe.
Photo Mark Thiessen, National Geographic
