The Molonglo Observatory Synthesis Telescope is equipped with a transient event monitoring system which operates during normal synthesis observations. The device is designed to respond to impulsive signals which occur within the passband (843.0 ± 1.5 MHz) with time scales between 0.001 ms and 800 ms. The multiple beam facility of the telescope provides some discrimination against local interference. An upper limit of 1.7 × 10−2 events s−1 sr−1 has been placed on celestial events with durations between 1 ms and 25 ms and energy density ≥ 10−28 J m−2 Hz−1. The monitoring system has been recently reconfigured to improve the recognition and rejection of impulsive signals of non-celestial origin.

The extended radio source 0319-453 (MSH 03-43) was observed with the Molonglo Observatory Synthesis Telescope as part of a program to study a large sample of southern extragalactic radio sources. The low level structure showed a ridge pointing towards the nearby source 0317-456, which also showed low level structure. It is suggested that the two sources are the asymmetric lobes of a radio galaxy identified with the magnitude 15 peculiar dust-land galaxy AM 0319-452. The galaxy redshift of z = 0.0633 and the radio size of 25.6 arcmin give a projected size of 1.27 Mpc (H = 100 kms−1 Mpc−1). Thus it is one of the largest radio galaxies.

A model is explored for energy release in solar flares that involves a constant coronal current. An emerging flux tube is assumed to carry a current I≲1012 A, and this current is assumed not to change during flare. Using a circuit model, explosive energy release is attributed to a rapid rise in the coronal resistance Rc, which must adjust to Rc = − Lc, with Lc the rate of change of the coronal inductance Lc, to ensure I = constant. In this model the total energy released in the corona is twice the change in the magnetic energy stored in the corona. It is argued that this energy is inadequate to power a large flare and the implications of this conclusion are discussed.

In 1931 Karl Jansky established that radio noise was associated with our own galaxy–the Milky Way. For a decade and a half there was little follow-up; those of us who were associated with low frequency radar during the war regarded it as a nuisance which could limit the detection range of enemy aircraft. Grote Reber was the first to make a detailed but fairly low resolution map of the radiation from the galaxy showing, for the first time, some detailed structure. The event which we celebrate today occurred when Gordon Stanley, Bruce Slee and I showed that three of the discrete sources that we had discovered could be identified with visual objects. One was with the Crab Nebula, a supernova remnant within our own galaxy and the other two with galaxies, far beyond our own system, in the constellations of Virgo and Centaurus. Thus began extragalactic radio astronomy. In 1982 at the Noosa meeting of the ASA, I gave an account of those early years, later to be published in the ASA Proceedings. As I don’t wish to repeat myself, I propose to speak on my involvement in a later development which was to extend the observable scale of the universe to look-back times as great as the age of the oldest stars in our own system. The first important step was Graham Smith’s identification of Cygnus A with a galaxy that was much fainter than our two. The spectrum by Minkowski revealed an instrinsically highly-luminous galaxy with strong emission lines and opened up the possibility of discovering similar objects at significantly greater distance. This was achieved nine years later with the building of the Owens Valley Observatory and my title of ‘Radiophysics in Exile’ comes from the fact the observatory owed its existence and early successes very largely to past and future staff members of Radiophysics. They were, in order of appearance, J. G. Bolton, G. J. Stanley, K. C. Westfold, J. A. Roberts, V. Radhakrishnan, D. Morris and K. I. Kellermann. Some still bear . the scars–Westfold left the tip of one index finger in the Owens Valley!

A general method is described for estimating the position, integrated flux density and the second moments of the flux density distribution for sources in a two dimensional map. The method requires accurate knowledge of the beam shape of the telescope. Uncertainty estimates and significance levels of the source parameters are easily obtained.

The Logo of the Australia Telescope National Facility (ATNF) depicts a linear array of six antennas in the Southern Hemisphere. Precision measurement of this image implies that the Compact Array is located at latitude 37° south and azimuth 176°; this corresponds (surprisingly) to an approximately north-south array. Furthermore, the ATNF Logo was apparently prepared at LST 04h 00m.

Variation of the electric current profile as a means of energy release in a solar flare is investigated. In particular, the change in magnetic energy is calculated for some simple idealized cases of the current profile. It is suggested that current profile changes may explain the smallest observed energy release structures in a flare.

The Molonglo Observatory Synthesis Telescope (MOST), operating at 843 MHz, is currently surveying the southern galactic plane (245° <l<360°, −1.5° ≤b≤ +1.5°). The resulting maps provide images of the radio continuum with a synthesised beamwidth of 43′′ × 43′′ cosec δ and a noise level of about 1mJy. The survey involves 12-hour synthesis observations of over four hundred fields on a predefined set of field centres. About half the fields have been observed to date, and the survey is scheduled for completion in 1990. A noteable feature in many of the fields is the occurrence of widespread diffuse filamentary structure, in addition to the expected supernova remants and HII regions.

When metre wavelength radars were first operated in the 1940s, echoes were obtained which could be attributed to backscatter from ionised trains produced by the ablation of meteroids in the upper atmosphere at altitudes near 100 km. Modern over-the-horizon skywave radars operating in the HF (High Frequency) band employ digital techniques for both radar control and signal processing and are aided by frequency management subsystems for the selection of appropriate frequencies for meteor detection based on real-time monitoring of the HF signal environment.

This paper describes the results of using such a radar for meteor observations. We report the detection of the Eta Aquarid meteor shower and demonstrate that a large increase in the echo rate due to sporadic meteors is obtained as frequencies are reduced below 15 MHz and the underdense echo ceiling rises in altitude. Finally, we present preliminary observations of highly Doppler shifted echoes which travel at meteoric velocities and which we identify as meteor ‘head echoes’.

A program to determine accurate radio positions and optical identifications of southern flat-spectrum radio sources has been undertaken with the six-dish array of the Fleurs synthesis telescope at 1.4 GHz and using the SERC J sky survey. This sample covers the declination range −80° to −50° and comprises all 198 sources from the Parkes catalogue with α of > −0.5 and flux density of 0.25 Jy.

The radio astrometric phase of the program is complete. We conclude that by comparison with accurate VLBI positions the FST positions have r.m.s. uncertainties of ∼0″.9. There is no global bias in the FST positions at the 0″.2 to 0″.3 level relative to the JPL VLBI extragalactic reference frame. A comparison with positions from the Parkes catalogue shows that in the southern regions the Parkes catalogue has rms position errors of about 9″. There is no significant bias between the FST and Parkes positions.

Data from the Solar Maximum Mission satellite suggests that there is a 0.1 percent variation in solar luminosity over the 11-year solar cycle with maximum output corresponding to maximum sunspot number. Tree ring chronologies can be utilized as proxy data to compile a record of the magnitude of past solar variability. Spectral analysis of tree ring series compiled from a site in Tasmania has established, among others, significant periodicities of about 90 and 11 years. The application of band pass filter techniques shows that the 11-year cycle present in some tree ring series correlates with the Zurich sunspot numbers over the period from AD1700, the extent of accurate sunspot records, with a time lag of about three years.

The radio source G357.7-0.1 has commonly been regarded as a galactic supernova remnant; alternative interpretations have concentrated on the pronounced brightness gradient along its major axis. Analysis of our new map shows that this brightness gradient masks an even more crucial characteristic – symmetry about the centre – the key to a totally different interpretation.

This paper discusses the techniques of presenting data both verbally, with emphasis on the use of viewgraphs, and as posters. The views expressed summarise a discussion which involved about 40 young astronomers: they are of particular relevance to those amongst us of the generation which has had these media thrust upon it without training.

A graphical format has been adopted to depict some characteristic variations associated with the solar activity cycle up to 1988, for both the Zurich annual and monthly mean values over the respective periods from 1700 and 1750. Both low pass and band pass filtering techniques have been employed to smooth the data, the autocorrelation coefficients determined for a high number of lags to illustrate the secular modulation of the maximum values in each cycle and the spectral amplitudes computed to establish periodicities in the chronologies.

8.4 GHz linear polarization maps, obtained with the Parkes radio telescope, are presented for six southern supernova remnants. These results are compared with published and unpublished polarization maps at 5 GHz to derive the magnetic field direction and Faraday rotation measure distribution.

These results are part of a program to map the magnetic fields in galactic supernova remnants and complement our program to obtain high-resolution maps of galactic SNRs using the Molonglo Observatory Synthesis Telescope; five new Molonglo maps are presented here.

The probability of a collision with each of the terrestrial planets due to each of the Aten-Apollo-Amor asteroids discovered through to 1989 May is calculated; the range of possible impact velocities is also given in each case. For Mercury there are eight possible impactors known, with a mean collision probability of 1.30 × 10−9 per year; for Venus, the 32 planet-crossing asteroids give a mean collision probability of 9.63 × l0−9 per year; for the Earth the corresponding figures are 65 and 6.93 × 10−9 per year; and for Mars, 116 and 3.41 × 10−10 per year. The rate for Mars does not include the full range of Mars-crossers (i.e. those of 1.30<perihelion distance <1.67 AU are not included here), and for the interior planets any undiscovered population of asteroids would also alter the mean probability of an impact.

‘History is Bunk’ said Henry Ford. He was exaggerating but it is well recognized that the connection between history and truth is tenuous. Even very recent history dependent on human memory is notoriously unreliable despite the intention of the historian to tell the truth.

In radio astronomy we are fortunate in having a dedicated historian-astronomer by the name of Woody Sullivan who has spent years in interviewing and reinterviewing astronomers to find out the real facts about the early years of the subject. Because of Sullivan’s work (e.g. Sullivan 1988) and because so many of my former colleagues have written histories of the period I felt very doubtful about adding my piece to the saga when asked to do so. However, I did accept the invitation to do so after I had read a statement about radio astronomy written by our usually very well informed Minister for Science, Barry Jones (Jones 1987). This statement which I shall quote later is an example of what we may call popular history.