A supersynthesis radio telescope for neutral hydrogen spectroscopy at the dominion radio astrophysical observatory

A radio telescope designed for studies of the 21-cm line of neutral hydrogen is described. It combines the techniques of aperture synthesis and digital correlation spectrometry to achieve an angular resolution of 1 arc min within an area of sky of 2° diameter and a frequency resolution variable from 3 to 100 kHz with 80 channels. The telescope comprises four 9-m paraboloids, two fixed and two movable on a 300-m precision E-W track. The system noise is 80 K. Remote local oscillators are controlled in phase to about 1 degree independent of the electrical lengths of distributing cables. An on-line computer provides source positions, and controls telescope tracking, local-oscillator frequency and phase, and incremental delay compensation. It also performs the Fourier transformation of the correlation coefficients and the data logging. The digital correlator uses 3 by 5 level quantization which reduces signal-to-noise degradation due to quantization to a factor 1.16. The telescope sensitivity for emission and absorption studies is discussed and first results are presented.