Science at the performance limits of the Hubble Space Telescope

As with any large telescope on the ground, HST will often be used at the limits of its performance capabilities. The actual performance will only be determined once HST is i n orbit, but detailed modeling based on mirror, structure, and control system characteristics gives a reasonable assessment of the expected performance. The purpose of this paper is to present (1) selected image characteristics expected for HST, (2) performance limits for selected instrument characteristics, and (3) examples of observations for which the performance limits are approached. Among the image features noted are point spread functions, encircled energy curves, and image diameters for selected wavelengths. Performance limits discussed include expected limiting magnitude and resolution of close point sources as a function of wavelength, each for selected camera focal ratios and pixel dimensions. Examples of observations discussed include a binary in which one component is faint and the detectability of a single luminous star at large distances.