HERA is located in the South African Karoo Astronomy Reserve, with a nominal array centre of 30°43’17″S and 21°25’42″E – the location of the existing Precision Array for Probing the Epoch of Reionisation (PAPER).
PAPER listens in on both the Northern and Southern hemisphere skies. The primary 128-antenna instrument is at the SKA site in the Karoo, while its smaller 32-antenna cousin is in West Virginia in the United States.
While PAPER is a pathfinder experiment (also known as HERA phase I) consisting of small antennas only a few metres across, each of HERA’s 331 antennas will measure 14 metres in diameter and boast a collecting area roughly 30 times larger. Bigger antennas mean that HERA will have a smaller field-of-view than PAPER, but it will be much more sensitive to the faint signals from the epoch of reionisation. Each antenna measures dual polarisation and they are referred to as dipole antennas.
HERA works on the same interferometry principles as KAT-7, MeerKAT and the SKA: essentially, data from all its antennas are combined. The instrument also shares much of the supporting infrastructure being constructed for MeerKAT and the SKA, including the underlying technology of the digital back-end, which processes and packages the incoming analogue radio signals so that astronomers can glean information and create visual images using digital data.
The current PAPER container will be moved to a location just west of HERA and the correlator will be moved to the Karoo Array Processor Building (KAPB). PAPER will be decommissioned over the HERA construction period.