The High Speed Photometer (HSP) is a scientific instrument formerly installed on the Hubble Space Telescope. The HSP was designed to measure the brightness and polarity of rapidly varying celestial objects. It could observe in ultraviolet, visible light, and near infrared at a rate of one measurement per 10 microseconds. The design was novel in that despite being able to view through a variety of filters and apertures, it had no moving parts "except for electrons" as principal investigator Prof. Robert Bless was fond of saying. Filter and aperture selection was accomplished using image dissector tubes and the HST pointing system. It was functional from launch in 1990 until it was removed at the end of 1993, and it helped diagnose an issue with the Hubble's primary mirror.