One of the basic tasks of the one-mile cross at the Molonglo Radio Observatory is the compilation of a catalogue of radio sources complete to a low flux density level. This level has been tentatively chosen as 0.2 f.u., which is well above the ultimate detection level which can be reached in selected areas of sky. Such a limitation is necessary if the catalogue is to be restricted to a manageable number of sources; a few tens of thousands, which will be achieved with the above limit, seems appropriate and useful at the present time.

The extremely rare occurrence of a relatively nearby supernova, SN 1987A, provides astronomers with a unique opportunity to conduct the most detailed multi-wavelength analysis of this event and its effect on the ambient medium. Looking inside the supernova, astronomers are getting their first ‘unbiased’ view of the composition of the expanding ejecta. The infrared (IR) region of the spectrum can carry the signature of products ranging from heavy elements, synthesised during the early phases of the expansion, to molecules and dust formed after the ejecta underwent significant cooling. Probing the ambient medium, IR observers can gain information on the presence and distribution of dust in close proximity (∼1 pc) to the supernova (SN), and on the interaction of the SN blast wave with the surrounding dusty medium. At larger distances from the SN, they can set constraints on dust properties in the scattering dust layers detected at distances of ∼120 and ∼330 pc from the supernova.

The tropopause, typically at 16 to 18 km altitude at the lower latitudes, dips down to only 8 km in the polar regions, allowing access to the cold, dry and nonturbulent lower stratosphere by tethered aerostats. These can float as high as 12 km, have long operating lifetimes, and are extremely reliable. In contrast to free-flying balloons, they can stay on station for weeks at a time, and payloads can be safely recovered for maintenance and adjustment and relaunched in a matter of hours. We propose to use such a platform, located first near Fairbanks, Alaska, and later in the Antarctic, to operate a new-technology 4 m telescope with diffraction-limited performance in the near infrared. Thanks to the low ambient temperature (~200 K), thermal emission from the optics is of the same order as that of the zodiacal light in the 2–3 μm band. Since this wavelength interval is the darkest part of the zodiacal light spectrum from optical wavelengths to 100 μm, the combination of high-resolution images and a very dark sky make it the spectral region of choice for observing galaxies, QSOs and clusters of galaxies at the formation epoch of galaxies.

The LYMAN Observatory payload is mounted on a service module which which offers pointing, power and telemetry and which has substantial commonality with the SOHO concept. The payload consists of a Wolter-Schwartzschild Type II Grazing Incidence telescope with monolithic primary and secondary elements feeding far-UV and extreme-UV spectrographs. It is designed to offer an effective collecting area of greater than 10 cm2 over a limited field of view with a spectral resolution on astronomical targets of 30000 in the prime ( λ900 - 1250 Å ) spectral range. This will allow high-resolution observations on sources as faint as 15 mag. LYMAN will also be capable of high resolution observations up to 1800Å, and will offer low-resolution spectroscopy in the extreme-UV down to about 100Å.

The usual method of calculating corrections for precession nutation and aberration involves the use of the precession constants M, N, m, n and the Day Numbers A, B, C, D, E, J, J’. For the computer analysis of radio source data obtained with the Molonglo Telescope it seemed desirable to compute the corrections directly from the basic formulae, thus avoiding the trouble and possibility of accidental error in copying out the Day Numbers for each day’s observation. In this paper we quote in full the equations that are used in the analysis of the Molonglo data. These equations are abstracted from The Explanatory Supplement to the Astronomical Ephemeris and Smart’s Spherical Astronomy, and expressed in a form which parallels the organization of the computer routine. In addition to the observed position, the only other data required to compute the precession nutation and aberration corrections is the Julian date (J.D.). This basic parameter in the equations is very simply calculated to the required accuracy of a few minutes from the time and date of the observation. The computer routine that computes the corrections occupies 1350 words of programme in the KDF9 computer and takes 200 msec to compute one position. If a large number of computations are being carried out on continuous data, then the average time per computation is only 5 msec as a full computation of the coefficients does not have to be made for each point separately.

It is now well established that observations of interplanetary scintillation from a single station can yield useful information on the angular structure of radio sources, and on the propagation of large-scale disturbances through the interplanetary medium. However, when it is required to obtain detailed information on the plasma properties single station observations suffer from the disadvantage that, in general, it is not possible to measure the velocity and scale of the irregularities independently. For example, a change in the width of the observed temporal power spectrum of the scintillations might be caused by either a change in velocity, or a change in scale, or a combination of both.

The X-ray Timing Explorer (XTE) is a NASA satellite designed to perform high-time-resolution studies of known X-ray sources. The two main experiments are a large-area proportional counter array (PCA) from the Goddard Space Flight Center (GSFC) and a high-energy X-ray timing experiment (HEXTE) from the University of California at San Diego (UCSD). The PCA data is processed by an electronic data system (EDS) built by the Massachusetts Institute of Technology (MIT) that performs many parallel processing analysis functions for on-board evaluation and data compression. MIT also provide an all-sky monitor (ASM) experiment so that XTE can be slewed rapidly to new transient sources. The spacecraft provides a mean science telemetry rate for the PCA of ~20 kilobits per second (kbps), with bursts to 256 kbps for durations of 30 minutes. Photons are tagged to 1 μs and absolute timing should be better than 100 μs. XTE is due for launch in late August 1995 and the first NASA Research Announcement (NRA) is due out in January 1995. This paper summarises XTE’s performance and then discusses the interactive and flexible operations of the satellite and some of the science it can do. These features should make XTE a productive spacecraft for coordinated observation programs.

Figure 1 shows the spectrum of 3C279 (1253-05) in mid-1966 derived from observations at frequencies of 467, 630, 960, 1410, 2650 and 5000 MHz made by Batchelor, Brooks, Cooper, Milne, Roberts and the author with the CSIRO 210 ft. telescope. The figure also shows the spectrum obtained in 1964 by Kellermann with the same telescope. All the flux densities have been measured relative to a number of calibration sources on a scale previously determined by Kellermann. Although our flux densities are preliminary, further analysis should not change them significantly.

The discrepancy between the observed and predicted flux of neutrinos from the Sun is well known. Past attempts at reconciling this difference have been unconvincing (Kuchowicz 1976, Rood 1978), and hence investigations in this area continue.

Very sensitive low-noise amplifiers designed to receive transmissions from spacecraft are not necessarily suitable receivers for radio astronomy. In the former case a good signalto- noise ratio is required so that high data rates can be achieved. In the latter the ratio of signal to noise power may be as low as 10-4 and the stability of receiver gain and that of ail sources of noise during long integration times become of equal importance.

This paper describes a novel solution to the problem, which allowed important astronomy to be performed while the ruby maser receivers belonging to the European Space Agency were installed on the Parkes radio telescope for an extended period of time.

Observations of galactic HII regions in the longitude range 280° to 300° have recently been made at the OH-line frequencies 1612.231, 1665.402 and 1667.358 MHz using the Parkes radio telescope. Strong emission was observed at 1612 and 1665 MHz from a source near the regions of Hα emission RCW 48 and RCW 49 (Rodgers, Campbell and Whiteoak).

Prompted by recent moves to ask the International Astronomical Union to redefine the System III rotation period, we have used all available dekametric observations from 1951 to 1975 and new analysis methods in an attempt to improve our estimate of the Jovian dekametric rotation period.

In the preceding paper, Cannon has outlined the observational evidence for the existence of a distinct concentration of stars near the base of the red giant branch in intermediate-age galactic clusters, which he tentatively identifies with the core helium burning phase of evolution occurring after the helium flash. This paper reports preliminary results of evolutionary calculations to test this identification.

Since the computation of hydrogen shell-burning evolution up the red giant branch is extremely time-consuming, the present calculations have been commenced at the stage immediately following the helium flash. It is assumed that no overall mixing occurs at the flash, so that the composition discontinuity at the hydrogen-burning shell remains sharp. The initial stellar composition was set at (X, Y, Z) = (0.68, 0.30, 0.02), corresponding to Population I material.

It is now generally accepted that the remnants of supernovae (SNRs) are of two types, recognizable by their radio structure and spectral index. To date most of the radio sources identified as SNRs are of the easily identified shell type. These have spectral indices a of -0.5 ±0.2 and exhibit some degree of annular brightness distribution — the projection of the radio shell. The second type, e.g. the Crab Nebula, have filled structures and relatively flat (a = -0.1 ±0.1) spectral indices. The relatively strong radio polarization exhibited by some members of this class has led to their identification but generally they tend to be hidden amongst the HII regions in our galaxy.

For a spherically symmetrical distribution of gaseous matter in gravitational equilibrium the total pressure, density and other physical variables are all functions of the radial distance measured from the centre.