The SHEVE observations have shown that the compact source at the nucleus of Pictor A has a core-jet structure approximately 10 pc in extent. A flat-spectrum core lies at the eastern end of the structure and a steep-spectrum jet extends toward the west, highly aligned with the kpc-scale jet and the western radio hotspot. In the highest resolution image the jet is resolved into an inner continuous jet and a detached component. Future VLBI observations of comparable quality and resolution will make an investigation of evolution in the pc-scale source possible.
Regardless, the pc-scale radio structure of Pictor A can be compared with existing high resolution optical observations.
The pc-scale core-jet radio structure aligns with a sub-arcsecond optical jet reported by Simkin, Robinson, and Sadler [1992] from narrow band HST imaging. They found that [OIII] emission from the narrow line region of the Pictor A host galaxy is distributed in a roughly symmetrical fashion around the nucleus, while the line-free continuum takes the form of an elongated, jet-like structure aligned with the western radio lobe. They measure the optical jet to have dimensions of 50 
220 mas.
On one hand, the coincidence of the optical jet with the pc-scale radio jet supports the suggestion of Simkin, Robinson, and Sadler [1992] that the optical jet is due to synchrotron emission.
However, the optical jet appears to be much more extended than the pc-scale radio jet seen with VLBI. Figure 3.1 shows that the radio jet extends only approximately 50 mas whereas the quoted length of the optical jet is in excess of 200 mas. Given that the electrons responsible for optical synchrotron emission are much shorter lived than those responsible for radio synchrotron emission it is not clear that the optical jet can be more extended than the radio jet. In fact a very good correspondence between radio and optical jets has been established, at least on kpc-scales. HST and radio imaging of the radio/optical jets in Virgo A and PKS 0521-365 [Sparks, Biretta, & Macchetto 1994; Macchetto et al. 1991] show a strong coincidence between the jet structure at radio and optical wavelengths.
To show that the VLBI observations were not biased towards measuring a jet shorter than in reality, Figure 3.4 shows an image produced from simulated data. The data were simulated from the Caltech VLBI task FAKE using a source model which consisted of a 5 mas full width at half maximum (FWHM) circular Gaussian core component of 0.4 Jy and a 200 mas long and 50 mas wide constant surface brightness elliptical component of 0.7 Jy, orientated at a position angle of 
. The source was given the RA and DEC of the Pictor A nucleus and ``observed'' at 2.290 GHz with the array of telescopes used on 1991 March 12. Realistic values for system temperatures, antenna diameters and antenna pointing were used to generate noise in the data. In Figure 3.4, the jet component can be easily detected to its full 200 mas extent, showing that the observations of 1991 March 12 would have been sensitive to a jet with the extent of the optical jet reported by Simkin, Robinson, and Sadler [1992].
Figure: Map peak, 0.4 Jy/beam. Contours, -1, 1, 2, 4, 8, 16, 32, and 64% of peak. Beam FWHM, 32.5 13.3 mas @ -87.1 
.
Thus, based on a simple synchrotron interpretation, the relationship between the VLBI observations and the HST observations is difficult to understand. A second epoch observation, with the post COSTAR HST, of the optical jet will be required before a detailed comparison between the optical and VLBI observations can be made.
The HST has also been used to observe the western hotspot, the site of interaction between jet and inter galactic medium (IGM), at optical wavelengths. Even though the results of the attempt to detect the hotspot of Pictor A with VLBI, described in 
3.2, were ambiguous, Pictor A remains one of the best candidates for such a detection. Thompson, Crane, & MacKay [1995] present a VLA image of the western hotspot in Pictor A which reveals radio emission unresolved with a 0.''8 0.''2 beam. This emission should be detectable and imagable with 2.3 GHz VLBI observations utilising an array similar to that used for Figure 3.1. With the higher bandwidth of the S2 VLBI system a better sensitivity to the hotspot emission will be possible. The resulting images would give a view of the interaction between the jet and IGM at a resolution comparable to the HST observations. These observations have been proposed as future SHEVE experiments.
As one of the closest powerful radio galaxies, Pictor A will be an important target for future investigations with VLBI and at other wavelengths. Observations of the compact radio core of Pictor A with the VLBI Space Observatory Programme (VSOP) space VLBI mission may be feasible. As an FR II radio galaxy with a bright core it offers one of the best prospects for the investigation of a misaligned and non beamed radio jet with the long baselines provided by the upcoming space VLBI missions.