The SHEVE array is an ad hoc array of radio telescopes in the Southern Hemisphere. The facilities which make up and support the array are owned and operated by several independent institutions. Thus, operation of the SHEVE array is based heavily on collaboration and cooperation between these institutions. The first SHEVE observations were made in 1982 [Preston et al. 1989; Meier et al. 1989; Tzioumis et al. 1989; Jauncey et al. 1989]. In Tables 2.1, 2.2, and 2.3, a brief summary of the array is given, including the telescopes which regularly participate and their characteristics (further information is available on the World Wide Web, http://wwwatnf.atnf.csiro.au).
An open proposal system is in place for obtaining observing time with the SHEVE array, administered by the Australia Telescope National Facility (ATNF). SHEVE observations are generally made three or four times per year, each session typically of one to two weeks in duration. Due to the collaborative nature of the SHEVE operation each investigator is required to participate in the observations, as well as be responsible for processing the results of the observations they propose.
Table 2.1: SHEVE antenna locations
Table 2.2: SHEVE baseline lengths in km
Table 2.3: SHEVE antenna characteristics
Up until 1994 all SHEVE observations were made using either the narrow bandwidth Mark II VLBI recording system [Clark 1973] or the wide bandwidth Mark III VLBI recording system [Rogers et al. 1983]. Imaging observations utilised the Mark II setup since all telescopes were equipped for Mark II. Mark III VLBI observations are generally only utilised for astrometric or geodetic observations (e.g. Reynolds et al. 1994) since only a subset of the SHEVE telescopes are equipped with Mark III recorders. Seven of the SHEVE telescopes are equipped with Hydrogen masers as the frequency standard for VLBI observations. The remaining telescopes are equipped with Rubidium clocks, as indicated in Table 2.3.
All of the Mark II data obtained for the work included in this thesis were recorded with a single sideband and a single circular polarisation, according to IEEE convention. The standard observing frequencies were used: 2.290, 4.851, and 8.418 GHz, with RCP, LCP, and RCP respectively.
The SHEVE array recording system has recently been upgraded to the S2 system [Wietfeldt et al. 1991] which uses a low-cost recording medium and hardware similar to the Mark II system but has a much larger recorded bandwidth. Most future SHEVE observations will be made with the S2 system.