The Hubble Space Telescope (HST) is a cooperative program of the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA) to operate a space-based observatory for the benefit of the international astronomical community. HST is an observatory first dreamed of in the 1940s, designed and built in the 1970s and 80s, and operational only in the 1990s. Since its preliminary inception, HST was designed to be a different type of mission for NASA--a long term space-based observatory. To accomplish this goal and protect the spacecraft against instrument and equipment failures, NASA had always planned on regular servicing missions. Hubble has special grapple fixtures, 76 handholds, and is stabilized in all three axes. The 2.4-meter (about 8 feet) reflecting telescope was deployed in low-Earth orbit (600 kilometers, or about 380 miles) by the crew of the space shuttle Discovery (STS-31) on 25 April 1990. Servicing missions in 1993, 1997, 1999, and 2002 were enormous successes. The telescope is expected to have a mission duration of up to 20 years.
Responsibility for conducting and coordinating the science operations of the Hubble Space Telescope rests with the Space Telescope Science Institute (STScI) on the Johns Hopkins University Homewood Campus in Baltimore, Maryland. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc. (AURA).
HST's complement of science instruments include three cameras, two spectrographs, and fine guidance sensors (primarily used for astrometric observations). Because of HST's location above the Earth's atmosphere, these science instruments can produce high resolution images of astronomical objects. In the past, ground-based telescopes were seldom able to provide resolution better than 1.0 arc seconds, except momentarily under the very best observing conditions. With its new corrective optics (COSTAR) installed at the first Hubble servicing mission in 1993, HST's resolution is about 10 times better, or 0.1 arc seconds.
Recent advances in optical interferometry and active optical systems, however, have vastly expanded the ability of modern ground-based telescopes (like Keck and the VLT) to resolve ultra-fine detail, and these have recently started to surpass the HST's abilities in some problem areas requiring only very narrow spatial range. The HST is still capable of working in wavelength regimes not accessible to the ground, and so it is an effective and critical partner with major ground-based optical and radio instrumentation as well as the x-ray instrumentation aboard Chandra.
The HST's original Wide Field Planetary Camera, Faint Object Spectrograph, and backup primary mirror, almost identical to the one currently in orbit, can be seen on display in the Digital Age section of the Explore the Universe gallery.
Portions adapted from the Hubble Space Telescope Website