The Cosmic Background Imager consists of 13 separate radio antennas on a single mount that can be pointed to a particular direction in space. Each antenna is a 90-cm parabolic reflector enclosed in a shield can and protected by a teflon cover that is transparent to radio radiation. The signals from each pair of antennas are combined in a correlator which rejects the constant part of the microwave background and radiation from the ground and the atmosphere. CREDIT: CBI / Caltech / NSF
