THE PARKES 21 CM MULTIBEAM RECEIVER

Several extragalactic HI surveys using a lambda 21 cm 13-beam focal pl ane array will begin in early 1997 using the Parkes 64 m telescope. Th ese surveys are designed to detect efficiently nearby galaxies that ha ve failed to be identified optically because of low optical surface br ightness or high optical extinction. We discuss scientific and technic al aspects of the multibeam receiver, including astronomical objective s, feed, receiver and correlator design and data acquisition. A compar ison with other telescopes shows that the Parkes multibeam receiver ha s significant speed advantages for any large-area lambda 21 cm galaxy survey in the velocity range range 0-14 000 km s(-1).