During 1992 we have obtained HST Planetary Camera (PC) images of a magnitude limited sample of 12 elliptical galaxies in the Virgo cluster (Jaffe et al. 1994, van den Bosch et al. 1994, Ferrarese et al. 1994). The aim of our project is to study the morphological properties of the inner region, derive the core brightness profiles, and look for evidence of nuclear mass concentrations and photometrically decoupled cores. In order to accomplish these goals the full capabilities of HST are needed. In fact, ground based observations are severely impaired by atmospheric seeing; it has been established (Peletier et al. 1990) that seeing effects can extend to radii 5 to 10 times the seeing FWHM, which is unacceptable considering that typical core radii are of the order of only a few arcsec at the distance of the Virgo cluster.
Unfortunately, the spherical aberration affecting the HST primary mirror can seriously alter the morphological and photometric properties of the cores. In the past three years, deconvolution techniques have been extensively improved in order to suit HST data, nevertheless, it is a legitimate doubt to assume that there are cases in which deconvolution may not give satisfactory answers or, even worse, may introduce spurious effects. We have therefore built an extensive set of model elliptical galaxies to test whether deconvolution techniques are able to restore the original surface brightness parameters of the cores, i.e., ellipticity, position angle of the major axis, deviations of the isophotes from pure ellipses, and brightness profile. In this paper, we will discuss the results obtained for the brightness profile, and refer to a separate paper for the results on the other surface brightness parameters (van den Bosch et al. 1994).