The Precision Array for Probing the Epoch of Reionization: PAPER, in South Africa

The spectral line characteristics of the ground state of neutral hydrogen provides a probe into the dynamical environment of the early universe. The expansion of the universe over time will Doppler shift the frequency of the hydrogen radiation that had occurred during this epoch from a rest frequency of 1,420.4 MHz down to below 100 MHz, yielding a mechanism by which the structure of the universe may be studied over time. At present, it is a theoretical possibility, but is it practical? The radiation from the hydrogen is extremely weak and originates from the outer reaches of a universe filled with radiating electrons producing a wall of foreground radiation that is many orders of magnitude stronger than that from the hydrogen. In addition, signals from terrestrial and satellite sources in the 50-200 MHz band are powerful and plentiful. Despite the odds, several groups of scientists and engineers from around the world are attempting this very challenging astrophysical measurement that has important cosmological implications.

The Precision Array for Probing the Epoch of Reionization (PAPER) is a path-finding instrument deployed in South Africa, designed to help guide the development of the measurement process and perhaps even obtain a glimpse of the hydrogen signal itself. From its inception, the goal of PAPER was to build a body of knowledge that assimilates the technology, methodology, and science to yield insight into the requirements for the next generation experiment. An overview of the PAPER project will be presented, highlighting the many lessons learned throughout this evolutionary, path-finding journey and explain how these finding will shape things to come.