The Hubble Space Telescope's high-speed photometer

We present an overview of the performance of the High Speed Photometer (HSP), one of the five original instruments on the Hubble Space Telescope (HST). As its name implies, the HSP was designed for precise high time resolution photometry from visual to ultraviolet wavelengths; sample times as short as 10.7 mu s were possible. Three image dissectors along with 23 different broad- and narrowband filters spanning the spectral range from 1200 to 7500 Angstrom were used for photometry of stars and galaxies. A fourth image dissector with associated polarization analyzers allowed the measurement of broadband linear polarization at near-ultraviolet wavelengths. Simultaneous observations in the blue and red could be made using one of the dissectors and a photomultiplier. Except for an instability in the sensitivity of one of the image dissectors and a reduced throughput in a specialized observational mode, the instrument met or exceeded operational specifications until it was removed from HST in 1993 December. The ability of HSP to carry out its primary program, however, was nearly totally compromised by the poor performance of the telescope, i.e., the spherical aberration of the primary mirror that greatly amplified the effects of large spacecraft pointing jitter and telescope "breathing." As a consequence, the real possibility of HST/HSP opening a new era of astronomical photometry was lost. HSP data affected by various telescope problems, as well as data in which these complications were relatively small, are shown. The excellent condition of the HSP after its return to Earth is described briefly.