This project will develop and operate an Air Cherenkov Telescope (ACT) at South Pole Station for the purpose of studying discreet astrophysical sources of very high energy (VHE) gamma rays. The instrument will consist of an array of parabolic mirrors, with photomultiplier tubes at their foci, which can detect light from VHE interactions in a small volume of the atmosphere. The experiment will shed light on the origin of cosmic rays and possibly on sources of exotic radiation, if such radiation exists. ACT will complement the existing South Pole Air Shower Experiment (SPASE), and extend downward by two to three orders of magnitude the energy threshold of SPASE. SPASE can survey most of the southern sky, and ACT will be able to focus on small regions of suspected activity. The location at South Pole will allow ACT to view a single object for extended periods (weeks to months) through a constant thickness of atmosphere, while mid-latitude locations allow only a few hours of viewing at a time of a given object. Since the atmosphere is the detector, the importance of viewing through a constant thickness cannot be over emphasized. The project is a collaboration of the University of Wisconsin, Purdue University, Columbia University, Bartol Research Institute of the University of Delaware, Smithsonian Astrophysical Observatory and the University of Florence (Firenze, Italy). It is jointly funded by NSF's Divisions of Polar Programs and Physics, the Italian Antarctic Program, the Wisconsin Alumni Research Foundation and the Smithsonian Astrophysical Observatory.
