Hubble: An Overview of the Space Telescope

摘要

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 envisioned in the 1940s, designed and built in the 1970s and 80s, and operational since the 1990. 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 planned on regular servicing missions. Hubble has special grapple fixtures, 76 handholds, and is stabilized in all three axes. HST is a 2.4-meter reflecting telescope, which was deployed in low-Earth orbit (600 kilometers) by the crew of the space shuttle Discovery (STS-31) on 25 April 1990. 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 current complement of science instruments includes three cameras, two spectrographs, and fine guidance sensors (primarily used for accurate pointing, but also for astrometric observations). Because of HST's location above the Earth's atmosphere, these science instruments can produce high-resolution images of astronomical objects. Ground-based telescopes are limited in their resolution by the Earths atmosphere, which causes a variable distortion in the images. Hubble can observe ultraviolet radiation, which is blocked by the atmosphere and therefore unavailable to ground-based telescopes. In the infrared portion of the spectrum, the Earths atmosphere adds a great deal of background, which is absent in Hubble observations.