The cosmic anisotropy telescope

The Cosmic Anisotropy Telescope (CAT) is a 3-element radio interferometer of novel design for observing temperature fluctuations in the Cosmic Microwave Background Radiation. The three horn-reflector antennas each have a diameter of 70 em and are mounted on rails to provide baselines between 1 and 5 m. The instrument can observe in a 500 MHz bandwidth centred anywhere between 13 and 17 GHz and can reach a temperature sensitivity of a few μK per month of good observing. We have taken extreme care to ensure that uncalibrated instrumental offsets are absent at this level. CAT observations should provide both confirmation of primordial fluctuations on an angular scale of about 0.5 degree and strong constraints on current theories of galaxy formation.