|Hubble Space Telescope (HST)|
|Organization||NASA / ESA / STScI|
|Launch date||April 24, 1990|
|Deorbited||Likely between 2013 and 2021|
|Mass||11,110 kg (24,250 lb)|
|Type of orbit||Near-circular low Earth orbit|
|Orbit height||589 km (366 mi)|
|Orbit period||96–97 min|
|Orbit velocity||7,500 m/s (17,000 mph)|
|Acceleration due to gravity||8. Space Shuttle Discovery ( Orbiter Vehicle Designation: OV-103 is one of the three currently operational orbiters in the Space Shuttle fleet of STS-82 was a Hubble Space Telescope servicing mission by Space Shuttle ''Discovery''. The International Designator (or NSSDC ID) is an international naming convention for Satellites It consists of the launch year a 3-digit incrementing launch number The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program The European Space Agency ( ESA) established in 1975 is an intergovernmental organisation dedicated to the exploration of space, currently with 17 member The Space Telescope Science Institute ( STScI) is the science operations center for the Hubble Space Telescope (HST in orbit since 1990 and for the James Events 1479 BC - Thutmose III ascends to the throne of Egypt, although power effectively shifts to Hatshepsut (according to Year 1990 ( MCMXC) was a Common year starting on Monday (link displays the 1990 Gregorian calendar) A Low Earth Orbit (LEO is generally defined as an Orbit within the locus extending from the Earth’s surface up to an altitude of 2000 km 169 m/s² (26. 80 ft/s²)|
|Location||Low Earth orbit|
|Telescope style||Ritchey-Chretien reflector|
|Wavelength||Optical, ultraviolet, near-infrared|
|Diameter||2. The Ritchey-Chrétien telescope or RCT is a specialized Cassegrain telescope designed to eliminate coma, thus providing a relatively large field of view In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays Infrared ( IR) radiation is Electromagnetic radiation whose Wavelength is longer than that of Visible light, but shorter than that of 4 m (94 in)|
|Collecting area||approx. 4. 5 m² (46 ft²)|
|Focal length||57. The focal length of an optical system is a measure of how strongly it converges (focuses or diverges (diffuses Light. 6 m (189 ft)|
|ACS||optical survey camera|
|WFPC2||wide field optical camera|
|FGS||three fine guidance sensors|
http://www.nasa.gov/hubble · http://hubble.nasa.gov
http://hubblesite.org · http://www.spacetelescope.org
The Hubble Space Telescope (HST; also known colloquially as "the Hubble" or just "Hubble") is a space telescope that was carried into orbit by a Space Shuttle in April 1990. A colloquialism is an expression not used in formal speech, writing or Paralinguistics. A space observatory is any instrument in Outer space which is used for observation of distant planets galaxies and other outer space objects A Low Earth Orbit (LEO is generally defined as an Orbit within the locus extending from the Earth’s surface up to an altitude of 2000 km NASA 's Space Shuttle, officially called the Space Transportation System ( STS) is the Spacecraft currently used by the United States It is named for American astronomer Edwin Hubble. The United States of America —commonly referred to as the Historically Astronomy was more concerned with the classification and description of phenomena in the sky while Astrophysics attempted to explain these phenomena Edwin Powell Hubble ( November 20, 1889 – September 28, 1953) was an American astronomer. Although not the first space telescope, the Hubble is one of the largest and most versatile, and is well known as both a vital research tool and a public relations boon for astronomy. Astronomy (from the Greek words astron (ἄστρον "star" and nomos (νόμος "law" is the scientific study The HST is a collaboration between NASA and the European Space Agency, and is one of NASA's Great Observatories, along with the Compton Gamma Ray Observatory, the Chandra X-ray Observatory, and the Spitzer Space Telescope. The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program The European Space Agency ( ESA) established in 1975 is an intergovernmental organisation dedicated to the exploration of space, currently with 17 member NASA 's series of Great Observatories Satellites are four large powerful space-based Telescopes Each of the Great Observatories has had a similar size and The Chandra X-ray Observatory is a Satellite launched on STS-93 by NASA on July 23, 1999. The Spitzer Space Telescope (formerly the Space Infrared Telescope Facility, SIRTF) is an Infrared Space observatory. 
Space telescopes were proposed as early as the 1940s. The Hubble was funded in the 1970s, with a proposed launch in 1983, but the project was beset by technical delays, budget problems, and the Challenger disaster. The Space Shuttle Challenger disaster took place on January 28 1986 when ''Challenger'', a Space Shuttle operated by NASA, broke apart When finally launched in 1990, scientists found that the main mirror had been ground incorrectly, severely compromising the telescope's capabilities. However, after a servicing mission in 1993, the telescope was restored to its intended quality. Hubble's position outside the Earth's atmosphere allows it to take extremely sharp images with almost no background light. Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five In Astronomy, background commonly refers to the incoming light from an apparently empty part of the night Sky. Hubble's Ultra Deep Field image, for instance, is the most detailed visible-light image of the universe's most distant objects ever made. The Hubble Ultra Deep Field, or HUDF, is an image of a small region of space in the constellation Fornax, composited from Hubble Space Telescope Many Hubble observations have led to breakthroughs in astrophysics, such as accurately determining the rate of expansion of the universe. Astrophysics is the branch of Astronomy that deals with the Physics of the Universe, including the physical properties ( Luminosity, Hubble's law is the statement in Physical cosmology that the Redshift in light coming from distant galaxies is proportional to their distance
The Hubble is the only telescope ever designed to be serviced in space by astronauts. To date, there have been four servicing missions. Servicing Mission 1 took place in December 1993 when Hubble's imaging flaw was corrected. Servicing missions 2, 3, and 4 repaired various sub-systems and replaced many of the observing instruments with more modern and capable versions. However, following the 2003 Columbia Space Shuttle disaster, the fifth servicing mission was canceled on safety grounds. The Space Shuttle Columbia disaster occurred on February 1, 2003, when the Space Shuttle ''Columbia'' disintegrated over Texas After spirited public discussion, NASA reconsidered this decision, and administrator Mike Griffin gave the green light for one final Hubble servicing mission. For other people with the same name see Michael Griffin (disambiguation. This is now planned for October 2008.
The planned repairs to the Hubble will allow the telescope to function until at least 2013, when its successor, the James Webb Space Telescope (JWST), is due to be launched. The James Webb Space Telescope ( JWST) is a planned space Infrared observatory the successor to the aging Hubble Space Telescope. The JWST will be far superior to Hubble for many astronomical research programs, but will only observe in infrared, so it would complement (not replace) Hubble's ability to observe in the visible and ultraviolet parts of the spectrum. Infrared ( IR) radiation is Electromagnetic radiation whose Wavelength is longer than that of Visible light, but shorter than that of
In 1923, German scientist Hermann Oberth, considered one of the three fathers of modern rocketry along with Robert Goddard and Konstantin Tsiolkovsky, published "Die Rakete zu den Planetenräumen" ("The Rocket into Planetary Space"), which mentioned how a telescope could be propelled into Earth orbit by a rocket. Robert Hutchings Goddard, PhD ( October 5, 1882 &ndash August 10 1945 U 
The history of the Hubble Space Telescope can be traced back as far as 1946, when the astronomer Lyman Spitzer wrote the paper "Astronomical advantages of an extraterrestrial observatory". Historically Astronomy was more concerned with the classification and description of phenomena in the sky while Astrophysics attempted to explain these phenomena Lyman Strong Spitzer Jr ( June 26, 1914 &ndash March 31, 1997) was an American theoretical physicist.  In it, he discussed the two main advantages that a space-based observatory would have over ground-based telescopes. First, the angular resolution (smallest separation at which objects can be clearly distinguished) would be limited only by diffraction, rather than by the turbulence in the atmosphere, which causes stars to twinkle and is known to astronomers as seeing. Angular resolution describes the resolving power of any image forming device such as an optical or Radio telescope, a Microscope, a Camera Diffraction is normally taken to refer to various phenomena which occur when a wave encounters an obstacle Astronomical seeing refers to the blurring and twinkling of astronomical objects such as stars caused by Turbulence in the Earth's atmosphere At that time ground-based telescopes were limited to resolutions of 0. 5–1. 0 arcseconds, compared to a theoretical diffraction-limited resolution of about 0. A minute of arc, arcminute, or MOA is a unit of angular measurement, equal to one sixtieth (1/60 of one degree. 05 arcsec for a telescope with a mirror 2. A mirror is an object with a surface that has good Specular reflection; that is it is smooth enough to form an Image. 5 m in diameter. Second, a space-based telescope could observe infrared and ultraviolet light, which are strongly absorbed by the atmosphere. Infrared ( IR) radiation is Electromagnetic radiation whose Wavelength is longer than that of Visible light, but shorter than that of Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays
Spitzer devoted much of his career to pushing for a space telescope to be developed. In 1962 a report by the United States National Academy of Sciences recommended the development of a space telescope as part of the space program, and in 1965 Spitzer was appointed as head of a committee given the task of defining the scientific objectives for a large space telescope. The National Academy of Sciences (NAS is a corporation in the United States whose members serve Pro bono as "advisers to the nation on science A human spaceflight is a Spaceflight with a human crew, and possibly passengers 
Space-based astronomy had begun on a very small scale following World War II, as scientists made use of developments that had taken place in rocket technology. World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including A rocket or rocket vehicle is a Missile, Aircraft or other Vehicle which obtains Thrust by the reaction of the The first ultraviolet spectrum of the Sun was obtained in 1946. The electromagnetic (EM spectrum is the range of all possible Electromagnetic radiation frequencies The Sun (Sol is the Star at the center of the Solar System.  An orbiting solar telescope was launched in 1962 by the United Kingdom as part of the Ariel space program, and in 1966 National Aeronautics and Space Administration (NASA) launched the first Orbiting Astronomical Observatory (OAO) mission. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located Ariel 3 was the first artificial Satellite designed and constructed in the United Kingdom. The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program The Orbiting Astronomical Observatory (OAO Satellites were a series of four space observatories launched by NASA between 1966 and 1972 which provided the first high-quality OAO-1's battery failed after three days, terminating the mission. It was followed by OAO-2, which carried out ultraviolet observations of stars and galaxies from its launch in 1968 until 1972, well beyond its original planned lifetime of one year. A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth A galaxy is a massive gravitationally bound system consisting of Stars an Interstellar medium of gas and dust, and Dark matter 
The OAO missions demonstrated the important role space-based observations could play in astronomy, and 1968 saw the development by NASA of firm plans for a space-based reflecting telescope with a mirror 3 m in diameter, known provisionally as the Large Orbiting Telescope or Large Space Telescope (LST), with a launch slated for 1979. A reflecting telescope (also called a reflector) is an Optical telescope which uses a single or combination of Curved mirrors that reflect Light These plans emphasized the need for manned maintenance missions to the telescope to ensure such a costly program had a lengthy working life, and the concurrent development of plans for the reusable Space Shuttle indicated that the technology to allow this was soon to become available. NASA 's Space Shuttle, officially called the Space Transportation System ( STS) is the Spacecraft currently used by the United States 
The continuing success of the OAO program encouraged increasingly strong consensus within the astronomical community that the LST should be a major goal. Consensus has two common meanings One is a general agreement among the members of a given group or Community, each of which exercises some discretion in In 1970 NASA established two committees, one to plan the engineering side of the space telescope project, and the other to determine the scientific goals of the mission. Once these had been established, the next hurdle for NASA was to obtain funding for the instrument, which would be far more costly than any Earth-based telescope. The US Congress questioned many aspects of the proposed budget for the telescope and forced cuts in the budget for the planning stages, which at the time consisted of very detailed studies of potential instruments and hardware for the telescope. The United States Congress is the bicameral Legislature of the federal government of the United States of America, consisting of two houses In 1974, public spending cuts instigated by Gerald Ford led to Congress cutting all funding for the telescope project. Government spending or government expenditure is classified by economists into three main types Gerald Rudolph Ford Jr (July 14 1913 December 26 2006 was the thirty-eighth President of the United States, serving from 1974 to 1977 and the fortieth Vice President 
In response to this, a nationwide lobbying effort was coordinated among astronomers. Many astronomers met congressmen and senators in person, and large scale letter-writing campaigns were organized. The United States House of Representatives is one of the two chambers of the United States Congress; the other is the Senate. The United States Senate is the Upper house of the bicameral United States Congress, the Lower house being the House of Representatives The National Academy of Sciences published a report emphasizing the need for a space telescope, and eventually the Senate agreed to half of the budget that had originally been approved by Congress. 
The funding issues led to something of a reduction in the scale of the project, with the proposed mirror diameter reduced from 3 m to 2. 4 m, both to cut costs and to allow a more compact and effective configuration for the telescope hardware. A proposed precursor 1. 5 m space telescope to test the systems to be used on the main satellite was dropped, and budgetary concerns also prompted collaboration with the European Space Agency. The European Space Agency ( ESA) established in 1975 is an intergovernmental organisation dedicated to the exploration of space, currently with 17 member ESA agreed to provide funding and supply one of the first generation instruments for the telescope, as well as the solar cells that would power it, and staff to work on the telescope in the United States, in return for European astronomers being guaranteed at least 15% of the observing time on the telescope. A solar cell or photovoltaic cell is a device that converts Solar energy into Electricity by the photovoltaic effect.  Congress eventually approved funding of US$36,000,000 for 1978, and the design of the LST began in earnest, aiming for a launch date of 1983. The United States dollar ( sign: $; code: USD) is the unit of Currency of the United States; it has also been  In 1983 the telescope was named after Edwin Hubble, who made one of the greatest scientific breakthroughs of the 20th century when he discovered that the universe was expanding. Edwin Powell Hubble ( November 20, 1889 – September 28, 1953) was an American astronomer. The Universe is defined as everything that Physically Exists: the entirety of Space and Time, all forms of Matter, Energy The metric expansion of space is the averaged increase of metric (i 
Once the Space Telescope project had been given the go-ahead, work on the program was divided between many institutions. Marshall Space Flight Center (MSFC) was given responsibility for the design, development, and construction of the telescope, while the Goddard Space Flight Center was given overall control of the scientific instruments and ground-control center for the mission. George C Marshall Space Flight Center (MSFC the original home of NASA, is a lead center for propulsion, Space Shuttle propulsion Shuttle external fuel The Goddard Space Flight Center ( GSFC) is a major NASA space research laboratory established on May 1, 1959 as NASA's first space flight  MSFC commissioned the optics company Perkin-Elmer to design and build the Optical Telescope Assembly (OTA) and Fine Guidance Sensors for the space telescope. PerkinElmer Inc ( is an American multinational technology corporation focused in the business areas of Life and Analytical Sciences Optoelectronics, and Lockheed was commissioned to construct the spacecraft in which the telescope would be housed. The Lockheed Corporation (originally Loughead Aircraft Manufacturing Company was an American aerospace company founded in 1912 which merged with Martin Marietta 
The mirror and optical systems of the telescope were the most crucial and complex part, and were designed to exacting specifications. Optical telescopes typically have mirrors polished to an accuracy of about a tenth of the wavelength of visible light, but the Space Telescope was to be used for observations into the ultraviolet (shorter wavelengths) and was specified to be diffraction limited to take full advantage of the space environment. In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. The resolution of an optical imaging system like a Microscope or Telescope or Camera can be limited by multiple factors like imperfections in the lenses or misalignment Therefore its mirror needed to be polished to an accuracy of 10 nanometres, or about 1/65 of the wavelength of red light. The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International 
Perkin-Elmer intended to use extremely sophisticated computer-controlled polishing machines to grind the mirror to the required shape, but in case their cutting-edge technology ran into difficulties, NASA demanded that PE sub-contract to Kodak to construct a back-up mirror using traditional mirror-polishing techniques. Computer-aided manufacturing ( CAM) is the use of computer-based software tools that assist engineers and machinists in manufacturing or prototyping product components Eastman Kodak Company ( is an American multinational Public company which produces imaging and photographic materials and equipment  (The team of Kodak and Itek also bid on the original mirror polishing work. Itek was a high technology company specializing in special purpose optical systems primarily cameras optimized for high altitude operation Their bid called for the two companies to double-check each other's work, which would have almost certainly caught the polishing error that later caused such problems. ) The Kodak mirror is now on permanent display at the Smithsonian Institution. The Smithsonian Institution (smɪθsoʊnɪən is an educational and research institute and associated Museum complex administered and funded by the Government of . An Itek mirror built as part of the effort is now used in the 2. 4 m telescope at the Magdalena Ridge Observatory. 
Construction of the Perkin-Elmer mirror began in 1979, using ultra-low expansion glass. Glass in the common sense refers to a Hard, Brittle, transparent Solid, such as that used for Windows many To keep the mirror's weight to a minimum it consisted of inch-thick top and bottom plates sandwiching a honeycomb lattice. A honeycomb is a mass of Hexagonal Wax cells built by Honey bees in their nests to contain their larvae and stores of Honey and Mirror polishing continued until May 1981. NASA reports at the time questioned Perkin-Elmer's managerial structure, and the polishing began to slip behind schedule and over budget. To save money, NASA halted work on the back-up mirror and put the launch date of the telescope back to October 1984.  The mirror was completed by the end of 1981 with the addition of a reflective coating of aluminium 65 nm thick and a protective coating of magnesium fluoride 25 nm thick. WikipediaNaming Magnesium fluoride (MgF2 is a white crystalline Salt composed of one Magnesium Ion and two Fluoride ions and is used in the 
Doubts continued to be expressed about Perkin-Elmer's competence on a project of this importance as their budget and timescale for producing the rest of the OTA continued to inflate. In response to a schedule described as "unsettled and changing daily", NASA postponed the launch date of the telescope until April 1985. Perkin-Elmer's schedules continued to slip at a rate of about one month per quarter, and at times delays reached one day for each day of work. NASA was forced to postpone the launch date until first March and then September 1986. By this time the total project budget had risen to US$1. 175 billion. 
The spacecraft in which the telescope and instruments were to be housed was another major engineering challenge. It would have to adequately withstand frequent passages from direct sunlight into the darkness of Earth's shadow, which would generate major changes in temperature, while being stable enough to allow extremely accurate pointing of the telescope. A shadow is an area where direct light from a light source cannot reach due to obstruction by an object A shroud of multi-layer insulation keeps the temperature within the telescope stable, and surrounds a light aluminum shell in which the telescope and instruments sit. Multi-layer insulation, or MLI, is thermal insulation composed of multiple layers of thin sheets Within the shell, a graphite-epoxy frame keeps the working parts of the telescope firmly aligned. Carbon fiber reinforced plastic ( CFRP or CRP) is a very strong light and expensive Composite material or fiber reinforced plastic. 
While construction of the spacecraft in which the telescope and instruments would be housed proceeded somewhat more smoothly than the construction of the OTA, Lockheed still experienced some budget and schedule slippage, and by the summer of 1985, construction of the spacecraft was 30% over budget and three months behind schedule. An MSFC report said that Lockheed tended to rely on NASA directions rather than take their own initiative in the construction. 
When launched, the HST carried five scientific instruments: the Wide Field and Planetary Camera (WF/PC), Goddard High Resolution Spectrograph (GHRS), High Speed Photometer (HSP), Faint Object Camera (FOC) and the Faint Object Spectrograph (FOS). The Wide Field/Planetary Camera ( WFPC) (pronounced as wiffpick was a Camera installed on the Hubble Space Telescope. The Goddard High Resolution Spectrograph (GHRS or HRS was a Spectrograph installed on the Hubble Space Telescope. The High Speed Photometer ( HSP) was a scientific instrument installed on the Hubble Space Telescope. The Faint Object Camera ( FOC) was a Camera installed on the Hubble Space Telescope from launch in 1990 until 2002 The Faint Object Spectrograph (FOS was a Spectrograph installed on the Hubble Space Telescope. WF/PC was a high-resolution imaging device primarily intended for optical observations. It was built by NASA's Jet Propulsion Laboratory, and incorporated a set of 48 filters isolating spectral lines of particular astrophysical interest. An optical filter is a device which selectively transmits light having certain properties (often a particular range of Wavelengths that is range of Colours A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range compared The instrument contained eight CCD chips divided between two cameras, each using four CCDs. The "wide field camera" (WFC) covered an angularly large field at the expense of resolution, while the "planetary camera" (PC) took images at a longer effective focal length than the WF chips, giving it a greater magnification. The focal length of an optical system is a measure of how strongly it converges (focuses or diverges (diffuses Light.
The GHRS was a spectrograph designed to operate in the ultraviolet. A spectrometer is an Optical instrument used to measure properties of Light over a specific portion of the Electromagnetic spectrum, typically used It was built by the Goddard Space Flight Center and could achieve a spectral resolution of 90,000. The spectral resolution or resolving power of a Spectrograph, or more generally of a Frequency spectrum, is a measure of its power to resolve features  Also optimized for ultraviolet observations were the FOC and FOS, which were capable of the highest spatial resolution of any instruments on Hubble. Rather than CCDs these three instruments used photon-counting digicons as their detectors. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena FOC was constructed by ESA, while the Martin Marietta corporation built the FOS. Martin Marietta Corporation was founded in 1961 through the Merger of The Martin Company and American-Marietta Corporation.
The final instrument was the HSP, designed and built at the University of Wisconsin–Madison. It was optimized for visible and ultraviolet light observations of variable stars and other astronomical objects varying in brightness. For the astronomical object see Variable star. Variable Star is a 2006 novel written by Spider Robinson It could take up to 100,000 measurements per second with a photometric accuracy of about 2% or better. Photometry is a technique of Astronomy concerned with measuring the Flux, or intensity of an Astronomical object 's Electromagnetic 
HST's guidance system can also be used as a scientific instrument. Its three Fine Guidance Sensors (FGS) are primarily used to keep the telescope accurately pointed during an observation, but can also be used to carry out extremely accurate astrometry; measurements accurate to within 0. The Fine Guidance Sensor (FGS is an interferometric instrument on board the Hubble Space Telescope (HST that provides high-precision pointing information as input to the observatory's Astrometry is the branch of Astronomy that relates to precise measurements and explanations of the positions and movements of Stars and other celestial bodies 0003 arcseconds have been achieved. 
The Space Telescope Science Institute (STScI) is responsible for the scientific operation of the telescope and delivery of data products to astronomers. The Space Telescope Science Institute ( STScI) is the science operations center for the Hubble Space Telescope (HST in orbit since 1990 and for the James The Space Telescope Science Institute ( STScI) is the science operations center for the Hubble Space Telescope (HST in orbit since 1990 and for the James STScI is operated by the Association of Universities for Research in Astronomy (AURA) and is physically located in Baltimore, Maryland on the Homewood campus of Johns Hopkins University, one of the 32 US universities and 7 international affiliates that make up the AURA consortium. The Association of Universities for Research in Astronomy (AURA is a consortium of universities and other institutions that operates astronomical observatories and STScI was established in 1983 after something of a power struggle between NASA and the scientific community at large. NASA had wanted to keep this function "in-house", but scientists wanted it to be based in an academic establishment.  The Space Telescope European Coordinating Facility (ST-ECF), established at Garching bei München near Munich in 1984, provides similar support for European astronomers. The Space Telescope - European Coordinating Facility (ST-ECF is an institution which provides a number of support and service functions primarily for European observers of the NASA/ESA Also spelled " Garching bei Muenchen " (without "ü" Munich (München; Minga is the capital city of Bavaria, Germany.
One rather complex task that falls to STScI is scheduling observations for the telescope.  Hubble is situated in a low-Earth orbit so that it can be reached by the Space Shuttle for servicing missions, but this means that most astronomical targets are occulted by the Earth for slightly less than half of each orbit. In Shia Islam The Occultation is a term used to designate the hidden state of the Imam of the Time. Observations cannot take place when the telescope passes through the South Atlantic Anomaly due to elevated radiation levels, and there are also sizable exclusion zones around the Sun (precluding observations of Mercury), Moon and Earth. The South Atlantic Anomaly (or SAA is the region where Earth 's inner Van Allen radiation belt makes its closest approach to the planet's surface Radiation, as in Physics, is Energy in the form of waves or moving Subatomic particles emitted by an atom or other body as it changes from a higher energy The solar avoidance angle is about 50°, which is specified to keep sunlight from illuminating any part of the OTA. Earth and Moon avoidance is to keep bright light out of the FGSs and to keep scattered light from entering the instruments. If the FGSs are turned off, however, the Moon and Earth can be observed. Earth observations were used very early in the program to generate flat-fields for the WFPC1 instrument. There is a so-called continuous viewing zone (CVZ), at roughly 90 degrees to the plane of Hubble's orbit, in which targets are not occulted for long periods. Due to the precession of the orbit, the location of the CVZ moves slowly over a period of eight weeks. Precession refers to a change in the direction of the axis of a rotating object Because the limb of the Earth is always within about 30° of regions within the CVZ, the brightness of scattered earthshine may be elevated for long periods during CVZ observations. The phenomenon known as planetshine occurs when reflected Sunlight from a Planet illuminates the dark side of one of its moons Typically this
Because Hubble orbits in the upper atmosphere, its orbit changes over time in a way that is not accurately predictable. The density of the upper atmosphere varies according to many factors, and this means that Hubble's predicted position for six weeks' time could be in error by up to 4,000 km. Observation schedules are typically finalized only a few days in advance, as a longer lead time would mean there was a chance that the target would be unobservable by the time it was due to be observed. 
Engineering support for the Hubble is provided by NASA and contractor personnel at the Goddard Space Flight Center in Greenbelt, Maryland, 48 km south of the STScI. Greenbelt is a city in Prince George's County Maryland, United States. Hubble's operation is monitored 24 hours per day by four teams of flight controllers who make up Hubble's Flight Operations Team. 
In early 1986, the planned launch date of October that year looked feasible, but the Challenger disaster brought the US space program to a halt, grounding the Space Shuttle fleet and forcing the launch of Hubble to be postponed for several years. The Space Shuttle Challenger disaster took place on January 28 1986 when ''Challenger'', a Space Shuttle operated by NASA, broke apart The telescope had to be kept in a clean room, powered up and purged with nitrogen, until a launch could be rescheduled. This costly situation (about $6 million per month) pushed the overall costs of the project even higher. On the other hand, engineers used this time to perform extensive tests, swap out a possible failure prone battery, and make other improvements. 
Eventually, following the resumption of shuttle flights in 1988, the launch of the telescope was scheduled for 1990. On 24 April 1990, shuttle mission STS-31 saw Discovery launch the telescope successfully into its planned orbit. Events 1479 BC - Thutmose III ascends to the throne of Egypt, although power effectively shifts to Hatshepsut (according to Year 1990 ( MCMXC) was a Common year starting on Monday (link displays the 1990 Gregorian calendar) STS-31 was the thirty-fifth mission of the American Space Shuttle program, which launched the Hubble Space Telescope astronomical observatory into Space Shuttle Discovery ( Orbiter Vehicle Designation: OV-103 is one of the three currently operational orbiters in the Space Shuttle fleet of 
From its original total cost estimate of about US$400 million, the telescope had by now cost over $2. 5 billion to construct. Hubble's cumulative costs up to this day are estimated to be several times higher still, with US expenditure estimated at between $4. 5 and $6 billion, and Europe's financial contribution at €593 million (1999 estimate). 
Within weeks of the launch of the telescope, the images returned showed that there was a serious problem with the optical system. Although the first images appeared to be sharper than ground-based images, the telescope failed to achieve a final sharp focus, and the best image quality obtained was drastically lower than expected. Images of point sources spread out over a radius of more than one arcsecond, instead of having a point spread function concentrated within a circle 0. A point source is a single identifiable localized source of something The point spread function ( PSF) describes the response of an imaging system to a Point source or point object 1 arcsec in diameter as had been specified in the design criteria.  The detailed performance is shown in graphs from STScI illustrating the mis-figured PSFs compared to post-correction and ground based PSFs. 
Analysis of the flawed images showed that the cause of the problem was that the primary mirror had been ground to the wrong shape. Although it was probably the most precisely figured mirror ever made, with variations from the prescribed curve of no more than 1/65 of the wavelength of visible light, it was too flat at the edges. In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. The mirror was barely 2. 3 micrometres out from the required shape, but the difference was catastrophic, introducing severe spherical aberration, a flaw in which light reflecting off the edge of a mirror focuses on a different point from the light reflecting off its center. A micrometre ( American spelling: micrometer; symbol µm) is one millionth of a Metre, or equivalently one thousandth of a Millimetre spherical-aberration-diskjpg|thumb|300 px|left|A Point source as imaged by a system with negative (top zero (center and positive (bottom spherical aberration In Geometrical optics, a focus, also called an image point, is the point where Light rays originating from a point on the object converge. 
The effect of the mirror flaw on scientific observations depended on the particular observation—the core of the aberrated PSF was sharp enough to permit uniquely high-resolution observations of bright objects, and spectroscopy was largely unaffected. However, the loss of light to the large, out of focus halo severely reduced the usefulness of the telescope for faint objects or high contrast imaging. This meant that nearly all of the cosmological programs were essentially impossible since they required observation of exceptionally faint objects.  NASA and the telescope became the butt of many jokes, and the project was popularly regarded as a white elephant. A white elephant is a valuable possession which its owner cannot dispose of and whose cost (particularly cost of upkeep exceeds its usefulness (For instance, in the movie The Naked Gun 2½: The Smell of Fear, the Hubble was pictured with the Titanic, the Hindenburg, and the Edsel). The Naked Gun 2½ The Smell of Fear is a 1991 Comedy film starring Leslie Nielsen as the comically bumbling Police Lt Construction The Titanic was a White Star Line ocean liner built at the Harland and Wolff shipyard in Belfast, Ireland WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout The Edsel was a marquee division of Ford Motor Company during the 1958 1959 and 1960 model years  Nonetheless, during the first three years of the Hubble mission, before the optical corrections, the telescope still carried out a large number of productive observations. The error was well characterized and stable, enabling astronomers to optimize the results obtained using sophisticated image processing techniques such as deconvolution. Image processing is any form of Signal processing for which the input is an image such as photographs or frames of video the output of image processing can be either an image In Mathematics, deconvolution is an algorithm-based process used to reverse the effects of Convolution on recorded data 
A commission headed by Lew Allen, director of the Jet Propulsion Laboratory, was established to determine how the error could have arisen. General Lew Allen Jr (born September 30, 1925 in Miami Florida) was the tenth Chief of Staff of the United States Air Force. The Allen Commission found that the main null corrector, a device used to measure the exact shape of the mirror, had been incorrectly assembled—one lens was wrongly spaced by 1. null corrector is an optical device used in the testing of large aspheric mirrors 3 mm.  During the polishing of the mirror, Perkin-Elmer had analyzed its surface with two other null correctors, both of which (correctly) indicated that the mirror was suffering from spherical aberration. The company ignored these test results as it believed that the two null correctors were less accurate than the primary device which was reporting that the mirror was perfectly figured. 
The commission blamed the failings primarily on Perkin-Elmer. Relations between NASA and the optics company had been severely strained during the telescope construction due to frequent schedule slippage and cost overruns. NASA found that Perkin-Elmer had not regarded the telescope mirror as a crucial part of their business and were also secure in the knowledge that NASA could not take its business elsewhere once the polishing had begun. While the commission heavily criticized Perkin-Elmer for these managerial failings, NASA was also criticized for not picking up on the quality control shortcomings such as relying totally on test results from a single instrument. 
The design of the telescope had always incorporated servicing missions, and astronomers immediately began to seek potential solutions to the problem which could be applied at the first servicing mission, scheduled for 1993. While Kodak and Itek had each ground back-up mirrors for Hubble, it would have been impossible to replace the mirror in orbit, and too expensive and time-consuming to bring the telescope temporarily back to Earth for a refit. Instead, the fact that the mirror had been ground so precisely to the wrong shape led to the design of new optical components with exactly the same error but in the opposite sense, to be added to the telescope at the servicing mission, effectively acting as "spectacles" to correct the spherical aberration. Glasses, also called eyeglasses or spectacles, are frames bearing lenses worn in front of the Eyes normally for vision correction, 
The first step was a precise characterization of the error in the main mirror. Working backwards from images of point sources, astronomers determined that the conic constant of the mirror was −1. The conic constant is a quantity describing Conic sections and is represented by the letter K 01324, instead of the intended −1. 00230.  The same number was also derived by analyzing the null corrector used by Perkin-Elmer to figure the mirror, as well as by analyzing interferograms obtained during ground testing of the mirror. null corrector is an optical device used in the testing of large aspheric mirrors In physics interference is the addition ( superposition) of two or more Waves that result in a new wave pattern
Because of the way the instruments were designed, two different sets of correctors were required. The design of the Wide Field and Planetary Camera 2, already planned to replace the existing WF/PC, included relay mirrors to direct light onto the eight separate CCD chips making up its two cameras. The Wide Field and Planetary Camera 2 ( WFPC2) is a Camera installed on the Hubble Space Telescope. A charge-coupled device ( CCD) is an analog Shift register, that enables the transportation of analog signals (electric charges through successive stages (capacitors An inverse error built into their surfaces could completely cancel the aberration of the primary. However, the other instruments lacked any intermediate surfaces which could be figured in this way, and so required an external correction device. 
The system designed to correct the spherical aberration for light focused at the FOC, FOS, and GHRS was called the "Corrective Optics Space Telescope Axial Replacement" (COSTAR) and consisted essentially of two mirrors in the light path, one of which would be figured to correct the aberration. The Corrective Optics Space Telescope Axial Replacement (COSTAR is the instrument designed to correct Hubble Space Telescope ’s spherical aberration for light focused The Corrective Optics Space Telescope Axial Replacement (COSTAR is the instrument designed to correct Hubble Space Telescope ’s spherical aberration for light focused  To fit the COSTAR system onto the telescope, one of the other instruments had to be removed, and astronomers selected the High Speed Photometer to be sacrificed. 
The telescope had always been designed so that it could be regularly serviced, but after the problems with the mirror came to light, the first servicing mission assumed a much greater importance, as the astronauts would have to carry out extensive work on the telescope to install the corrective optics. STS-61 was the first Hubble Space Telescope servicing mission and the fifth flight of the Space Shuttle ''Endeavour''. The seven astronauts selected for the mission were trained intensively in the use of the hundred or so specialized tools which would need to be used.  The mission STS-61 of the Space Shuttle Endeavour took place in December 1993, and involved installation of several instruments and other equipment over a total of 10 days. STS-61 was the first Hubble Space Telescope servicing mission and the fifth flight of the Space Shuttle ''Endeavour''. A broader definition of a tool is an entity used to interface between two or more domains that facilitates more effective action of one domain upon the other
Most importantly, the High Speed Photometer was replaced with the COSTAR corrective optics package, and WFPC was replaced with the Wide Field and Planetary Camera 2 (WFPC2) with its internal optical correction system. The High Speed Photometer ( HSP) was a scientific instrument installed on the Hubble Space Telescope. The Corrective Optics Space Telescope Axial Replacement (COSTAR is the instrument designed to correct Hubble Space Telescope ’s spherical aberration for light focused The Wide Field and Planetary Camera 2 ( WFPC2) is a Camera installed on the Hubble Space Telescope. In addition, the solar arrays and their drive electronics were replaced, as well as four of the gyroscopes used in the telescope pointing system, two electrical control units and other electrical components, and two magnetometers. In the field of Photovoltaics, a photovoltaic module is a packaged interconnected assembly of photovoltaic cells also known as Solar cells An installation of A gyroscope is a device for measuring or maintaining orientation, based on the principles of Angular momentum. The onboard computers were upgraded, and finally, the telescope's orbit was boosted, to compensate for the orbital decay from 3 years of drag in the tenuous upper atmosphere. In Fluid dynamics, drag (sometimes called fluid resistance) is the force that resists the movement of a Solid object through a Fluid (a 
On January 13, 1994, NASA declared the mission a complete success and showed the first of many much sharper images. Events 532 - Nika riots in Constantinople. 888 - Odo Count of Paris becomes King of the Franks Year 1994 ( MCMXCIV) was a Common year starting on Saturday (link will display full 1994 Gregorian calendar)  The mission had been one of the most complex ever undertaken, involving five lengthy periods of extravehicular activity and its resounding success was an enormous boon for NASA, as well as for the astronomers who now had a fully capable space telescope.
Servicing Mission 2 Discovery (STS-82) in February 1997 replaced the GHRS and the FOS with the Space Telescope Imaging Spectrograph (STIS) and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS), replaced an Engineering and Science Tape Recorder with a new Solid State Recorder, repaired thermal insulation and again boosted Hubble's orbit. STS-82 was a Hubble Space Telescope servicing mission by Space Shuttle ''Discovery''. The Space Telescope Imaging Spectrograph ( STIS) is a Spectrograph installed on the Hubble Space Telescope, operating from 1997 to 2004 The Near Infrared Camera and Multi-Object Spectrometer ( NICMOS) is a scientific instrument for Infrared astronomy, installed on the Hubble Space Telescope  NICMOS contained a heat sink of solid nitrogen to reduce the thermal noise from the instrument, but shortly after it was installed, an unexpected thermal expansion resulted in part of the heat sink coming into contact with an optical baffle. A heat sink (or heatsink) is an environment or object that absorbs and dissipates heat from another object using Thermal contact (either direct or radiant Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Johnson–Nyquist noise ( thermal noise, Johnson noise, or Nyquist noise) is the electronic noise generated by the thermal agitation Thermal Expansion is the tendency of matter to change in Volume in response to a change in temperature This led to an increased warming rate for the instrument and reduced its original expected lifetime of 4. 5 years to about 2 years. 
Servicing Mission 3A Discovery (STS-103) took place in December 1999, split off from Servicing Mission 3 after three of the six onboard gyroscopes had failed. STS-103 was a Hubble Space Telescope servicing mission by Space Shuttle ''Discovery''. (A fourth failed a few weeks before the mission, rendering the telescope incapable of performing science observations. ) The mission replaced all six gyroscopes, replaced a Fine Guidance Sensor and the computer, installed a Voltage/temperature Improvement Kit (VIK) to prevent battery overcharging, and replaced thermal insulation blankets. The Fine Guidance Sensor (FGS is an interferometric instrument on board the Hubble Space Telescope (HST that provides high-precision pointing information as input to the observatory's  Although the new computer is hardly a powerhouse (a 25 MHz radiation hardened Intel 486 with 2 Megabytes of RAM), it is still 20 times faster, with 6 times more memory, than the DF-224 it replaced. Radiation hardening is a method of designing and testing electronic components and systems to make them resistant to damage or malfunctions caused by high-energy Subatomic particles The Intel 486, otherwise known as the 80486 i486 or just 486 was the first tightly pipelined X86 design The new computer increases throughput by moving some computing tasks from the ground to the spacecraft, and saves money by allowing the use of modern programming languages. 
Servicing Mission 3B Columbia (STS-109) in March 2002 saw the installation of a new instrument, with the FOC being replaced by the Advanced Camera for Surveys (ACS). STS-109 was the most recent NASA Space Shuttle mission to service the Hubble Space Telescope. The Advanced Camera for Surveys (ACS is a third generation axial instrument aboard the Hubble Space Telescope (HST It also saw the revival of NICMOS, which had run out of coolant in 1999. A coolant is a fluid which flows through a device in order to prevent its overheating transferring the heat produced by the device to other devices that utilize or dissipate it A new cooling system was installed which reduced the instrument's temperature enough for it to be usable again. Although not as cold as its original design called for, the temperature is more stable, in many ways a better tradeoff. . ACS in particular enhanced the Hubble's capabilities; it and the revived NICMOS together imaged the Hubble Ultra Deep Field. The Hubble Ultra Deep Field, or HUDF, is an image of a small region of space in the constellation Fornax, composited from Hubble Space Telescope
The mission replaced the solar arrays for the second time. The new arrays were derived from those built for the Iridium comsat system and were only two-thirds the size of the old arrays, resulting in less drag against the tenuous reaches of the upper atmosphere while providing 30% more power. The Iridium Satellite constellation is a system of 66 active communication Satellites with spares in orbit and on the ground The additional power allowed all instruments on board the Hubble to be run simultaneously, and reduced a vibration problem that occurred when the old, less rigid arrays entered and left direct sunlight. Hubble's Power Distribution Unit was also replaced in order to correct a problem with sticky relays, a procedure that required the complete electrical power down of the spacecraft for the first time since it was launched. 
Hubble has helped to resolve some long-standing problems in astronomy, as well as turning up results that have required new theories to explain them. For an object in the constellation of Canis Major also called Eagle nebula see Seagull Nebula. Hubble's law is the statement in Physical cosmology that the Redshift in light coming from distant galaxies is proportional to their distance Among its primary mission targets was to measure distances to Cepheid variable stars more accurately than ever before, and thus constrain the value of the Hubble constant, the measure of the rate at which the universe is expanding, which is also related to its age. A Cepheid variable (pron ˈse-f(ē-id or ˈsē-f(ē-id or Cepheid is a member of a particular class of Variable stars notable for a fairly tight correlation Hubble's law is the statement in Physical cosmology that the Redshift in light coming from distant galaxies is proportional to their distance Before the launch of HST, estimates of the Hubble constant typically had errors of up to 50%, but Hubble measurements of Cepheid variables in the Virgo Cluster and other distant galaxy clusters provided a measured value with an accuracy of 10%, which is consistent with other more accurate measurements made since Hubble's launch using other techniques. In Statistics and optimization, the concepts of statistical error and residual are easily confused with each other The Virgo Cluster is a cluster of galaxies at a distance of approximately 59 ± 4 Mly (18 
While Hubble helped to refine estimates of the age of the universe, it also cast doubt on theories about its future. Astronomers from the High-z Supernova Search Team and the Supernova Cosmology Project used the telescope to observe distant supernovae and uncovered evidence that, far from decelerating under the influence of gravity, the expansion of the universe may in fact be accelerating. The High-z Supernova Search Team was an international cosmology collaboration which used Type Ia Supernovae to chart the expansion of the Universe. The Supernova Cosmology Project is one of two research teams that determined the likelihood of an Accelerating universe and therefore a positive Cosmological constant A supernova (plural supernovae or supernovas) is a stellar Explosion. Gravitation is a natural Phenomenon by which objects with Mass attract one another The deceleration parameter q in cosmology is a Dimensionless measure of the cosmic acceleration of the expansion of the universe This acceleration was later measured more accurately by other ground-based and space-based telescopes which confirmed Hubble's finding, but the cause of this acceleration is currently very poorly understood.
The high-resolution spectra and images provided by the Hubble have been especially well-suited to establishing the prevalence of black holes in the nuclei of nearby galaxies. A black hole is a theoretical region of space in which the Gravitational field is so powerful that nothing not even Electromagnetic radiation (e While it had been hypothesized in the early 1960s that black holes would be found at the centers of some galaxies, and work in the 1980s identified a number of good black hole candidates, it fell to work conducted with the Hubble to show that black holes are probably common to the centers of all galaxies.  The Hubble programs further established that the masses of the nuclear black holes and properties of the galaxies are closely related. The legacy of the Hubble programs on black holes in galaxies is thus to demonstrate a deep and profound connection between galaxies and their central black holes.
The collision of Comet Shoemaker-Levy 9 with Jupiter in 1994 was fortuitously timed for astronomers, coming just a few months after Servicing Mission 1 had restored Hubble's optical performance. Shoemaker-Levy redirects here For other Shoemaker-Levy comets see List of periodic comets. Shoemaker-Levy redirects here For other Shoemaker-Levy comets see List of periodic comets. Hubble images of the planet were sharper than any taken since the passage of Voyager 2 in 1979, and were crucial in studying the dynamics of the collision of a comet with Jupiter, an event believed to occur once every few centuries. A planet, as defined by the International Astronomical Union (IAU is a celestial body Orbiting a Star or stellar remnant that is Voyager 2 is an unmanned Interplanetary Spacecraft launched on August 20, 1977.
Other major discoveries made using Hubble data include proto-planetary disks (proplyds) in the Orion Nebula; evidence for the presence of extrasolar planets around sun-like stars; and the optical counterparts of the still-mysterious gamma ray bursts. A protoplanetary disk (or proplyd) is a rotating Circumstellar disk of dense gas surrounding a young newly formed star a T Tauri star or Herbig star The Orion Nebula (also known as Messier 42, M42, or NGC 1976) is a Diffuse nebula situated south of Orion 's Belt An extrasolar planet, or exoplanet, is a Planet beyond the Solar System, orbiting around other Stars As of September 2008 312 Gamma-ray bursts ( GRB s are the most luminous electromagnetic events occurring in the Universe since the Big Bang.  HST has also been used to study objects in the outer reaches of the Solar System, including the dwarf planets Pluto and Eris. 
A unique legacy of Hubble is Hubble Deep Field and Hubble Ultra Deep Field images, which utilized Hubble's unmatched sensitivity at visible wavelengths to create images of small patches of sky which are the deepest ever obtained at optical wavelengths. The Hubble Deep Field (HDF is an image of a small region in the Constellation Ursa Major, based on the results of a series of observations by the Hubble The Hubble Ultra Deep Field, or HUDF, is an image of a small region of space in the constellation Fornax, composited from Hubble Space Telescope The Hubble Deep Field (HDF is an image of a small region in the Constellation Ursa Major, based on the results of a series of observations by the Hubble The Hubble Ultra Deep Field, or HUDF, is an image of a small region of space in the constellation Fornax, composited from Hubble Space Telescope The images reveal galaxies billions of light years away, and have generated a wealth of scientific papers, providing a new window on the early Universe.
Many objective measures show the positive impact of Hubble data on astronomy. The Hubble Ultra Deep Field, or HUDF, is an image of a small region of space in the constellation Fornax, composited from Hubble Space Telescope Over 4,000 papers based on Hubble data have been published in peer-reviewed journals, and countless more have appeared in conference proceedings. In academia proceedings are the collection of Academic papers that are published in the context of an Academic conference. Looking at papers several years after their publication, about one-third of all astronomy papers have no citations, while only 2% of papers based on Hubble data have no citations. A citation is a reference to a source (not always the original source published or unpublished(citation needed On average, a paper based on Hubble data receives about twice as many citations as papers based on non-Hubble data. Of the 200 papers published each year which receive the most citations, about 10% are based on Hubble data. 
Although the HST has clearly had a significant impact on astronomical research, the financial cost of this impact has been large. A study on the relative impacts on astronomy of different sizes of telescopes found that while papers based on HST data generate 15 times as many citations as a 4 m ground-based telescope such as the William Herschel Telescope, the HST costs about 100 times as much to build and maintain. The William Herschel Telescope or WHT was first conceived in the late 1960s when the Anglo-Australian Observatory was being designed 
Making the decision between investing in ground-based versus space-based telescopes in the future is complex. Advances in adaptive optics have extended the high-resolution imaging capabilities of ground-based telescopes to the infrared imaging of faint objects. Adaptive optics (AO is a Technology used to improve the performance of optical systems by reducing the effects of rapidly changing optical distortion The usefulness of adaptive optics versus HST observations depends strongly on the particular details of the research questions being asked. In the visible bands, adaptive optics can only correct a relatively small field of view, whereas HST can conduct high-resolution optical imaging over a wide field. Even before Hubble's launch, ground-based speckle imaging could provide higher resolution images of bright objects than Hubble can achieve, but Hubble's high resolution extends to dim objects as well. Speckle imaging (also known
Anyone can apply for time on the telescope; there are no restrictions on nationality or academic affiliation.  Competition for time on the telescope is extremely intense, and the ratio of time requested to time available (the oversubscription ratio) typically ranges between 6 and 9. 
Calls for proposals are issued roughly annually, with time allocated for a cycle lasting approximately one year. Proposals are divided into several categories; 'general observer' proposals are the most common, covering routine observations. 'Snapshot observations' are those in which targets require only 45 minutes or less of telescope time, including overheads such as acquiring the target; snapshot observations are used to fill in gaps in the telescope schedule which cannot be filled by regular GO programs. 
Astronomers may make 'Target of Opportunity' proposals, in which observations are scheduled if a transient event covered by the proposal occurs during the scheduling cycle. In addition, up to 10% of the telescope time is designated Director's Discretionary (DD) Time. Astronomers can apply to use DD time at any time of year, and it is typically awarded for study of unexpected transient phenomena such as supernovae.  Other uses of DD time have included the observations that led to the production of the Hubble Deep Field and Hubble Ultra Deep Field, and in the first four cycles of telescope time, observations carried out by amateur astronomers.
The first director of the STScI, Riccardo Giacconi, announced in 1986 that he intended to devote some of his Director Discretionary time to allowing amateur astronomers to use the telescope. Riccardo Giacconi (born October 6, 1931) is an Italian-born American Nobel Prize -winning Astrophysicist. Amateur astronomy, a subset of Astronomy, is a Hobby whose participants enjoy studying and observing celestial objects The total time to be allocated was only a few hours per cycle, but excited great interest among amateur astronomers. 
Proposals for amateur time were stringently peer reviewed by a committee of leading amateur astronomers, and time was awarded only to proposals that were deemed to have genuine scientific merit, did not duplicate proposals made by professionals, and required the unique capabilities of the space telescope. Peer review (also known as refereeing) is the process of subjecting an author's scholarly work research or Ideas to the scrutiny of others who are In total, 13 amateur astronomers were awarded time on the telescope, with observations being carried out between 1990 and 1997. One such study was Transition Comets -- UV Search for OH Emissions in Asteroids. Transition Comets — UV Search for OH Emissions in Asteroids was a study involving amateur Astronomers and the use of the Hubble Space Telescope. After that time, however, budget reductions at STScI made the support of work by amateur astronomers untenable, and no further amateur programs have been carried out. 
Hubble data were initially stored on the spacecraft. When launched, the storage facilities were old-fashioned reel-to-reel tape recorders, but these were replaced by solid state data storage facilities during servicing missions 2 and 3A. This article deals mainly with analog tape recorders for audio applications information on digital recording, recording of video signals, and A solid-state drive ( SSD) is a Data storage device that uses solid-state memory to store persistent Data. From the onboard storage facilities, data are transferred to the ground via the Tracking and Data Relay Satellite System, a system of satellites designed so that satellites in low-Earth orbit can communicate with their mission control facilities during about 85% of their orbit. The Tracking and Data Relay Satellite System ( TDRSS) is a network of Communications satellites (each called a Tracking and Data Relay Satellite Data are transmitted to the TDRSS ground station and then on to the Goddard Space Flight Center and finally to the Space Telescope Science Institute for archiving. 
All Hubble data are eventually made available via the archives of STScI. An archive refers to a collection of historical records and also refers to the location in which these records are kept . Data are usually proprietary—available only to the principal investigator (PI) and astronomers designated by the PI—for one year after being taken. A principal investigator ( PI) is the lead Scientist for a particular well-defined science (or other academic project such as an astronomical observing The PI can apply to the director of the STScI to extend or reduce the proprietary period in some circumstances. 
Observations made on Director's Discretionary Time are exempt from the proprietary period, and are released to the public immediately. Calibration data such as flat fields and dark frames are also publicly available straight away. A dark frame is a photography technique to identify noise in a CCD imaging device. All data in the archive are in the FITS format, which is suitable for astronomical analysis but not for public use. FITS or Flexible Image Transport System is a digital File format used to store transmit and manipulate scientific and other images  The Hubble Heritage Project processes and releases to the public a small selection of the most striking images in JPEG and TIFF formats. The Hubble Heritage Project was founded by a group of astronomers in 1998 
Astronomical data taken with CCDs must undergo several calibration steps before it is suitable for astronomical analysis. A charge-coupled device ( CCD) is an analog Shift register, that enables the transportation of analog signals (electric charges through successive stages (capacitors STScI has developed sophisticated software which automatically calibrates data when it is requested from the archive using the best calibration files available. This 'on-the-fly' processing means that large data requests can take a day or more to be processed and returned. The process by which data is calibrated automatically is known as 'pipeline reduction', and is increasingly common at major observatories. Astronomers may if they wish retrieve the calibration files themselves and run the pipeline reduction software locally. This may be desirable when calibration files other than those selected automatically need to be used. 
Hubble data can be analysed using many different packages. STScI maintains the custom-made STSDAS (Space Telescope Science Data Analysis System) software, which contains all the programs needed to run pipeline reduction on raw data files, as well as many other astronomical image processing tools, tailored to the requirements of Hubble data. The software runs as a module of IRAF, a popular astronomical data reduction program. IRAF (an acronym for I mage R eduction and A nalysis F acility is a huge collection of Software written by astronomers and by programmers 
It has always been important for the Space Telescope to capture the public's imagination, given the considerable contribution of taxpayers to its construction and operational costs.  After the difficult early years when the faulty mirror severely dented Hubble's reputation with the public, the first servicing mission allowed its rehabilitation as the corrected optics produced numerous remarkable images.
Several initiatives have helped to keep the public informed about Hubble activities. The Hubble Heritage Project was established to produce high-quality images for public consumption of the most interesting and striking objects observed. The Hubble Heritage Project was founded by a group of astronomers in 1998 The Heritage team is composed of amateur and professional astronomers, as well as people with backgrounds outside astronomy, and emphasizes the aesthetic nature of Hubble images. Aesthetics or esthetics ( also spelled æsthetics) is commonly known as the study of sensory or sensori-emotional values sometimes called The Heritage Project is granted a small amount of time to observe objects which, for scientific reasons, may not have images taken at enough wavelengths to construct a full-color image. 
In addition, STScI maintains several comprehensive websites for the general public containing Hubble images and information about the observatory. The outreach efforts are coordinated by the Office for Public Outreach, which was established in 2000 to ensure that US taxpayers saw the benefits of their investment in the space telescope program.
Since 1999, the leading Hubble outreach activities group in Europe has been the Hubble European Space Agency Information Centre (HEIC). The Hubble European Space Agency Information Centre (HEIC is a science communication office established at the Space Telescope - European Coordinating Facility (ST-ECF  This office was established at the Space Telescope - European Coordinating Facility (ST-ECF) in Munich, Germany. The Space Telescope - European Coordinating Facility (ST-ECF is an institution which provides a number of support and service functions primarily for European observers of the NASA/ESA HEIC's mission statement is to fulfill the Hubble Space Telescope outreach and education tasks for the European Space Agency (ESA). The European Space Agency ( ESA) established in 1975 is an intergovernmental organisation dedicated to the exploration of space, currently with 17 member The work is centered on the production of news and photo releases that highlight interesting Hubble science results and images. These are often European in origin, and so not only increase the awareness of ESA’s Hubble share (15%), but the contribution of European scientists to the observatory. The group also produces video releases and other innovative educational material.
There is a replica of the Hubble Telescope on the courthouse lawn in Marshfield, Missouri, the hometown of namesake Edwin P. Marshfield is a city in Webster County, Missouri, United States. Hubble.
Past servicing missions have exchanged old instruments for new ones, both avoiding failure and making possible new types of science. The Tarantula Nebula (also known as 30 Doradus, or NGC 2070) is an H II region in the Large Magellanic Cloud. The Large Magellanic Cloud (LMC is a nearby Satellite galaxy of our own galaxy the Milky Way. Without servicing missions, all of the instruments will eventually fail. On August 3, 2004, the power system of the Space Telescope Imaging Spectrograph (STIS) failed, rendering the instrument inoperable. Events 8 - Roman Empire General Tiberius defeats Dalmatians on the river Bathinus. "MMIV" redirects here For the Modest Mouse album see " Baron von Bullshit Rides Again " The Space Telescope Imaging Spectrograph ( STIS) is a Spectrograph installed on the Hubble Space Telescope, operating from 1997 to 2004 The electronics had originally been fully redundant, but the first set of electronics failed in May 2001.  Similarly, the main camera (the ACS) primary electronics failed on 25 June 2006, and the power supply for the backup electronics failed on January 27, 2007. The Advanced Camera for Surveys (ACS is a third generation axial instrument aboard the Hubble Space Telescope (HST Events 524 - Battle of Vézeronce, the Franks defeat the Burgundians Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 98 - Trajan becomes Roman Emperor after the death of Nerva. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century.  Only the instrument's Solar Blind Channel (SBC) is currently operable using the side-1 electronics. The two main channels, visible and UV, remain unusable.  It seems unlikely that any science functionality can be salvaged without a servicing mission.
HST uses gyroscopes to stabilize itself in orbit and point accurately and steadily at astronomical targets. A gyroscope is a device for measuring or maintaining orientation, based on the principles of Angular momentum. Normally, three gyroscopes are required for operation; observations are still possible with two, but the area of sky that can be viewed would be somewhat restricted, and observations requiring very accurate pointing would be more difficult. In 2005, it was decided to switch to two-gyroscope mode for regular telescope operations as a means of extending the lifetime of the mission. The switch to this mode was made on August 31, 2005, leaving Hubble with two gyroscopes in use, two on backup, and two inoperable. Events 1056 - Byzantine Empress Theodora becomes ill dying suddenly a few days later without children to succeed the Throne Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. Estimates of the failure rate of the gyros indicate that Hubble may be down to one gyro by 2008, after which the telescope would be rendered unusable. 
In addition to predicted gyroscope failure, Hubble will eventually require a change of batteries. In electronics a battery is a combination of two or more Electrochemical cells which store chemical Energy which can be converted into electrical energy A robotic servicing mission including this would be tricky, as it requires many operations, and a failure in any might result in irreparable damage to Hubble. However, the observatory was designed so that during Shuttle servicing missions it would receive power from a connection to the Space Shuttle, and this fact may be utilized by adding an external power source (an additional battery) rather than changing the internal ones. 
Hubble orbits the Earth in the extremely tenuous upper atmosphere, and over time its orbit decays due to drag. Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five Orbital decay is the process of prolonged reduction in the height of a satellite's Orbit. In Fluid dynamics, drag (sometimes called fluid resistance) is the force that resists the movement of a Solid object through a Fluid (a If it is not re-boosted by a shuttle or other means, it will re-enter the Earth's atmosphere sometime between 2010 and 2032, with the exact date depending on how active the Sun is and its impact on the upper atmosphere. The state of Hubble's gyros also impacts the re-entry date, as a controllable telescope can be oriented to minimize atmospheric drag. Not all of the telescope would burn up on re-entry. Parts of the main mirror and its support structure would probably survive, leaving the potential for damage or even human fatalities (estimated at up to a 1 in 700 chance of human fatality for a completely uncontrolled re-entry).  If STS-125 is successful, then the natural re-entry date range will be extended further as the mission would re-boost the telescope and replace its gyroscopes. STS-125 is a planned Space Shuttle mission which will be the fifth and final servicing mission to the Hubble Space Telescope (HST
NASA's original plan for safely de-orbiting Hubble was to retrieve it using a space shuttle (see STS-144). STS-144 was a proposed mission of the United States' Space Shuttle program to send the Space Shuttle Columbia to retrieve the Hubble Space Telescope from The Hubble telescope would then have most likely been displayed in the Smithsonian Institution. The Smithsonian Institution (smɪθsoʊnɪən is an educational and research institute and associated Museum complex administered and funded by the Government of This is no longer considered practical because of the costs of a shuttle flight (US$500 million by some estimates), the mandate to retire the space shuttles by 2010, and the risk to a shuttle's crew. Instead NASA looked at adding an external propulsion module to allow controlled re-entry.  The final decision was not to attach a de-orbit module on STS-125, but to add a grapple fixture so a robotic mission could more easily attach such a module later. 
Columbia was originally scheduled to visit Hubble again in February 2005. Space Shuttle Columbia ( NASA Orbiter Vehicle Designation: OV-102) was the first spaceworthy Space shuttle in NASA 's The tasks of this servicing mission would have included replacing a fine guidance sensor and two broken gyroscopes, placing protective "blankets" on top of torn insulation, replacing the Wide Field and Planetary Camera 2 with a new Wide Field Camera 3 and installing the Cosmic Origins Spectrograph (COS). The Wide Field and Planetary Camera 2 ( WFPC2) is a Camera installed on the Hubble Space Telescope. The Wide Field Camera 3 (WFC3 will be the Hubble Space Telescope 's (Hubble last and most technologically advanced instrument to take images in the visible spectrum The Cosmic Origins Spectrograph (COS is an instrument that is scheduled to be installed on the Hubble Space Telescope in October 2008 during STS-125. However, then-NASA Administrator Sean O'Keefe decided that, in order to prevent a repeat of the Columbia disaster, all future shuttles must be able to reach the 'safe-haven' of the International Space Station (ISS) should an in-flight problem develop which would preclude the shuttle from landing safely. Sean O'Keefe (born January 27, 1956) is a former Administrator of NASA, leading the space agency from December 2001 to February 2005 The Space Shuttle Columbia disaster occurred on February 1, 2003, when the Space Shuttle ''Columbia'' disintegrated over Texas The shuttle is incapable of reaching both the Hubble Space Telescope and the International Space Station during the same mission, and so future manned service missions were canceled. 
This decision was assailed by numerous astronomers, who felt that the Hubble telescope was valuable enough to merit the human risk. HST's successor, the James Webb Space Telescope (JWST), will not be ready until well after the 2010 scheduled retirement of the Space Shuttle. The James Webb Space Telescope ( JWST) is a planned space Infrared observatory the successor to the aging Hubble Space Telescope. While Hubble can image in the ultraviolet and visible wavelengths, JWST is limited to the infrared. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays Infrared ( IR) radiation is Electromagnetic radiation whose Wavelength is longer than that of Visible light, but shorter than that of The break in space-observing capabilities between the decommissioning of Hubble and the commissioning of a successor is of major concern to many astronomers, given the great scientific impact of HST taken as a whole.  The consideration that the JWST will not be located in low Earth orbit, and therefore cannot be easily repaired in the event of an early failure, only makes these concerns more acute. A Low Earth Orbit (LEO is generally defined as an Orbit within the locus extending from the Earth’s surface up to an altitude of 2000 km Nor can JWST's instruments be easily upgraded. On the other hand, many astronomers feel strongly that the servicing of Hubble should not take place if the costs of the servicing come from the JWST budget.
On 29 January 2004, O'Keefe said that he would review his decision to cancel the final shuttle servicing mission to HST due to public outcry and requests from Congress for NASA to look for a way to save it. Events 904 - Sergius III comes out of retirement to take over the papacy from the deposed Antipope Christopher. "MMIV" redirects here For the Modest Mouse album see " Baron von Bullshit Rides Again " On 13 July 2004, an official panel from the National Academy of Sciences made the recommendation that the Hubble be preserved despite the apparent risks. Events 1174 - William I of Scotland, a key rebel in the Revolt of 1173-1174, is captured at Alnwick by forces loyal to "MMIV" redirects here For the Modest Mouse album see " Baron von Bullshit Rides Again " The National Academy of Sciences (NAS is a corporation in the United States whose members serve Pro bono as "advisers to the nation on science Their report urged "NASA should take no actions that would preclude a space shuttle servicing mission to the Hubble Space Telescope". On August 11, 2004, O'Keefe requested the Goddard Space Flight Center to prepare a detailed proposal for a robotic service mission. Events 2492 BC - Traditional date of the defeat of Bel by Hayk, progenitor and founder of the Armenian nation "MMIV" redirects here For the Modest Mouse album see " Baron von Bullshit Rides Again " A robot is a mechanical or Virtual Artificial agent In practice it is usually an electro-mechanical system which by its appearance or movements These plans were later canceled, the robotic mission being described as "not feasible. " In late 2004, several Congressional members, led by Sen. Barbara Mikulski (D-MD), held public hearings and carried on a fight with much public support (including thousands of letters from school children across the country) to get the Bush Administration and NASA to reconsider the decision to drop plans for a Hubble rescue mission. 
The arrival in April 2005 of the new NASA Administrator, Mike Griffin, changed the status of the proposed shuttle rescue mission. For other people with the same name see Michael Griffin (disambiguation. At the time, Griffin stated he would reconsider the possibility of a manned servicing mission. Soon after his appointment, he authorized Goddard Space Flight Center to proceed with preparing for a manned Hubble maintenance flight, saying he would make the final decision on this flight after the next two shuttle missions. On October 31, 2006 Griffin gave the final go-ahead for the mission. Events 445 BC – Ezra reads the Book of the Law to the Israelites in Jerusalem (see Nehemiah 91 NLTse Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. The 11-day STS-125 mission by Atlantis, scheduled for launch on 8 October 2008, will install fresh batteries, replace all gyroscopes, and install Wide Field Camera 3 and the Cosmic Origins Spectrograph. STS-125 is a planned Space Shuttle mission which will be the fifth and final servicing mission to the Hubble Space Telescope (HST Space Shuttle Atlantis ( Orbiter Vehicle Designation: OV-104 is one of the three currently operational orbiters in the Space Shuttle fleet of The Wide Field Camera 3 (WFC3 will be the Hubble Space Telescope 's (Hubble last and most technologically advanced instrument to take images in the visible spectrum The Cosmic Origins Spectrograph (COS is an instrument that is scheduled to be installed on the Hubble Space Telescope in October 2008 during STS-125. 
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