A 5-GHz interferometer for microwave background studies

A description is given of a 5-GHz two-element very short baseline interferometer operated at Jodrell Bank for degree-scale studies of Galactic, point source and intrinsic cosmic microwave background emission. This is a high-sensitivity interferometer with 20-K system noise and a bandwidth of nearly 350 MHz. Its phase stability from day to day is better than 2° and allows independent data from separate days to be stacked. The interferometer gives receiver noise limited performance with an rms of 25 μK in 2min (0RA) from 26 d of data. The performance of the interferometer is illustrated with observations at Dec. = 40° for baselines of 11λ and 30λ. The astronomical potential of the interferometer is described.