A. D. Gray

The Parkes-MIT-NRAO Southern Sky Survey at 4850 MHz

G. Behrens, C. Chestnut, National Radio Astronomy Observatory, Greenbank, USA B. F. Burke, A. Fletcher, Massachusetts Institute of Technology, Cambridge, USA K. S. Russell, A. Savage, UK Schmidt Telescope, Anglo-Australian Observatory, Coonabarabran NSW 2357 J . L im, A. E. Vaughan, School of Mathematics and Physics, Macquarie University, North Ryde NSW 2113 S. Cote, Mount Stromlo and Siding Spring Observatories, Private Bag Weston ACT 2611 M. Anderson, A. Hons, G. L. White, Faculty of Science and Technology, University of Western Sydney, Kingswood NSW 2747 S. Amy, A. Burgess, S. Chan, L. Cram, A. Gray, W . Walsh, D. Campbell-Wilson, Astrophysics Department, University of Sydney, NSW 2006 V. Mclntyre, P. Randall, M. Suters, W. J. Zealey, Department of Physics, University of Wollongong, Wollongong NSW 2500

Radio emission from the Sun at 843 MHz

The Molonglo Observatory Synthesis Telescope (MOST) has recently been modified to permit observations of the Sun. With a collecting area of 18000 m2, MOST makes high-sensitivity measurements in right-hand circular polarisation over a 3 MHz bandwidth at 843 MHz. The maximum baseline of the multi-element interferometer is 1600 m, so that one-dimensional spatial resolution as fine as 32 arc sec is available. A resistor array produces simultaneously a set of 64 beams separated by 22 arc sec, which may be offset electronically to cover the entire Sun in a few seconds. Observations may be made with a beam shape corresponding to either a multiplying or an adding interferometer. By exploiting the technique of Earth-rotation synthesis the telescope may be used to make two-dimensional maps of the Sun at the time of the austral solstice with a synthesized beamwidth of 43 × 110 arc sec. This paper describes the instrument and the procedures used to make various types of solar observations, and exhibits some of the first data collected.

Solar Radio Observations at 843 MHz

The Molonglo Observatory Synthesis Telescope (MOST) has been used to observe the Sun with total-power fan-beams having a one-dimensional resolution of 41 arcsec at 843 MHz. The scans reveal clearly the rotation and evolution of the slowly-varying component as well as some burst activity. Low radio brightness features have also been identified, but the exact relationship between these features and coronal holes is, as yet, unclear. Several partial synthesis observations have been used to generate two-dimensional radioheliograms.