Redundant-Baseline Calibration of the Hydrogen Epoch of Reionization Array

Understand

In 21 cm cosmology, precision calibration is key to the separation of the neutral hydrogen signal from very bright but spectrally-smooth astrophysical foregrounds.

• The Hydrogen Epoch of Reionization Array (HERA), an interferometer specialized for 21 cm cosmology and now under construction in South Africa, was designed to be largely calibrated using the self-consistency of repeated measurements of the same interferometric modes.
• This technique, known as "redundant-baseline calibration" resolves most of the internal degrees of freedom in the calibration problem.
• It assumes, however, on antenna elements with identical primary beams placed precisely on a redundant grid.