Precision Array for Probing the Epoch of Reionization

rdf:langString Precision Array for Probing the Epoch of Reionization

rdf:langString The Donald C. Backer Precision Array for Probing the Epoch of Reionization (PAPER) is a radio interferometer funded by the National Science Foundation to detect 21 cm hydrogen (HI) fluctuations occurring when the first galaxies ionized intergalactic gas at around 500 Million years after the Big Bang. PAPER is a focused experiment aimed toward making the firststatistical detection of the 21 cm reionizationsignal. Given the stringent dynamic range requirements for detectingreionization in the face of foregrounds that are five orders ofmagnitude brighter, the PAPERproject is taking a carefully staged engineering approach, optimizingeach component in the array to mitigate, at the outset, anypotentially debilitating problems in subsequent data calibration andanalysis. This staged approach addresses theobservational challenges that arise fromvery-wide-field, high-dynamic-range imaging over wide bandwidthsin the presence of transient terrestrial interference.PAPER began as a collaboration between Don Backer of the UC Berkeley Radio Astronomy Laboratory and Richard Bradley of the National Radio Astronomy Observatory. With Backer's passing in 2010, Aaron Parsons has assumed leadership of PAPER on the side of UC Berkeley. The two fundamental concerns that most influence the design of any HIreionization detection instrument are removing foregrounds andachieving the requisite sensitivity. The PAPER approach heavilyemphasizes the former; the level of instrumental calibration andforeground characterization that will be required to model and removepolarized galactic synchrotron emission, continuum point-sources, andgalactic/extra-galactic free-free emission is unprecedented in the100-200 MHz band expected to encompass reionization. PAPER consists of two distinct arrays: one located at the NRAO site in Green Bank, WV, whichis used primarily for engineering investigations and field testing, and another located at theSouth African SKA site in the Karoo desert of the Northern Cape, South Africa., which is used for science observations.