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100-514: It constitutes the visible portions of the Cygnus Loop , a supernova remnant , many portions of which have acquired their own individual names and catalogue identifiers. The source supernova was a star 20 times more massive than the Sun which exploded between 10,000 and 20,000 years ago. At the time of the explosion, the supernova would have appeared brighter than Venus in the sky, and visible in

200-580: A spectral resolution of 90,000. 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. The FOC was constructed by ESA, while the University of California, San Diego , and Martin Marietta Corporation built

300-732: A 25 MHz Intel-based 80486 processor system during Servicing Mission 3A in 1999. The new computer is 20 times faster, with six times more memory, than the DF-224 it replaced. It increases throughput by moving some computing tasks from the ground to the spacecraft and saves money by allowing the use of modern programming languages. Additionally, some of the science instruments and components had their own embedded microprocessor-based control systems. The MATs (Multiple Access Transponder) components, MAT-1 and MAT-2, use Hughes Aircraft CDP1802CD microprocessors. The Wide Field and Planetary Camera (WFPC) also used an RCA 1802 microprocessor (or possibly

400-488: A back-up mirror using traditional mirror-polishing techniques. (The team of Kodak and Itek also bid on the original mirror polishing work. 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 problems .) The Kodak mirror is now on permanent display at the National Air and Space Museum . An Itek mirror built as part of

500-446: A cloud at the northern edge of the loop, to the east of the northern edge of Pickering's Triangle. NGC 6979 was reported by William Herschel , and while the coordinates he recorded for Veil objects were somewhat imprecise, his position for this one is tolerably close to the knot at J2000 RA 20 50 27.9 Dec +32° 01′ 33″. The identifier NGC 6979 is sometimes taken to refer to Pickering's Triangle, but

600-409: A compact stellar remnant have been largely concentrated here, as the hole may have been caused by the violent ejection of a neutron star. A detailed 2012 study of the blowout region identified a possible pulsar wind nebula, as well as a point-like source within it. Although at almost exactly the same position as a known Seyfert galaxy , the slight offset combined with a lack of a radio counterpart makes

700-419: A different point from the light reflecting off its center. 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 high-resolution observations of bright objects, and spectroscopy of point sources was affected only through a sensitivity loss. However, the loss of light to the large, out-of-focus halo severely reduced

800-586: A father of modern rocketry, along with Robert H. 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. The history of the Hubble Space Telescope can be traced to 1946, to astronomer Lyman Spitzer 's paper "Astronomical advantages of an extraterrestrial observatory". In it, he discussed

900-419: A filament. At the estimated distance of 2400 light-years, the nebula has a radius of 65 light-years (a diameter of 130 light-years). The thickness of each filament is 1 ⁄ 50,000 th of the radius, or about 4 billion miles, roughly the distance from Earth to Pluto. Undulations in the surface of the shell lead to multiple filamentary images, which appear to be intertwined. Even though

1000-437: 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 (PSF) concentrated within a circle 0.1  arcseconds (485 n rad ) in diameter, as had been specified in the design criteria. Analysis of the flawed images revealed that the primary mirror had been polished to

1100-546: A full-up start. There was some opposition on [Capitol] Hill to getting a new start on [Hubble]. It was driven, in large part as I recall, by the budget situation. Jim Fletcher proposed that we put in $ 5 million as a placeholder. I didn't like that idea. It was, in today's vernacular, a "sop" to the astronomy community. "There's something in there, so all is well". I figured in my own little head that to get that community energized we'd be better off zeroing it out. Then they would say, "Whoa, we're in deep trouble", and it would marshal

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1200-461: 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 National Academy of Sciences published a report emphasizing the need for a space telescope, and eventually, the Senate agreed to half the budget that had originally been approved by Congress. The funding issues led to

1300-554: A possibly failure-prone battery, and make other improvements. Furthermore, the ground software needed to control Hubble was not ready in 1986, and was barely ready by the 1990 launch. Following the resumption of shuttle flights, Space Shuttle Discovery successfully launched the Hubble on April 24, 1990, as part of the STS-31 mission. At launch, NASA had spent approximately US$ 4.7 billion in inflation-adjusted 2010 dollars on

1400-449: 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

1500-551: 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 (4 ft 11 in) 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 (ESA). ESA agreed to provide funding and supply one of

1600-565: A resolution of 0.64 megapixels. The wide field camera (WFC) covered a large angular 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 Goddard High Resolution Spectrograph (GHRS) was a spectrograph designed to operate in the ultraviolet. It was built by the Goddard Space Flight Center and could achieve

1700-507: A space-based reflecting telescope with a mirror 3 m (9.8 ft) in diameter, known provisionally as the Large Orbiting Telescope or Large Space Telescope (LST), with a launch slated for 1979. These plans emphasized the need for crewed 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

1800-478: A tenth of the wavelength of visible light , but the Space Telescope was to be used for observations from the visible through the ultraviolet (shorter wavelengths) and was specified to be diffraction limited to take full advantage of the space environment. Therefore, its mirror needed to be polished to an accuracy of 10 nanometers, or about 1/65 of the wavelength of red light. On the long wavelength end,

1900-403: A theoretical diffraction-limited resolution of about 0.05 arcsec for an optical telescope with a mirror 2.5 m (8 ft 2 in) in diameter. Second, a space-based telescope could observe infrared and ultraviolet light, which are strongly absorbed by the atmosphere of Earth . Spitzer devoted much of his career to pushing for the development of a space telescope. In 1962, a report by

2000-684: A very small scale following World War II , as scientists made use of developments that had taken place in rocket technology. The first ultraviolet spectrum of the Sun was obtained in 1946, and NASA launched the Orbiting Solar Observatory (OSO) to obtain UV, X-ray, and gamma-ray spectra in 1962. An orbiting solar telescope was launched in 1962 by the United Kingdom as part of the Ariel programme , and in 1966 NASA launched

2100-406: A way that is not accurately predictable. The density of the upper atmosphere varies according to many factors, and this means Hubble's predicted position for six weeks' time could be in error by up to 4,000 km (2,500 mi). Observation schedules are typically finalized only a few days in advance, as a longer lead time would mean there was a chance the target would be unobservable by the time it

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2200-650: A wide-field, far-ultraviolet nebular spectrometer, tuned to OVI emission lines , was launched aboard a Nike-Black Brant from White Sands Missile Range to observe the Cygnus Loop, the first observed galactic OVI emission line source. The X-ray source Cygnus X-5 coincides with SNR G074.0-08.6 (the Cygnus Loop), located at J2000 RA 20 51.1 Dec +30° 41′, observed by Uhuru at 4U 2046+31. This source also has catalogue numbers 1E 2049.4+3050, 1H 2050+310, and 1M 2051+309, having been observed by

2300-404: Is 6960, which runs behind 52 Cygni , a star that can be seen with the naked eye. NGC 6992 and 6995 are objects on the eastern side of the loop which are also relatively easy to see. NGC 6974 and NGC 6979 are visible as knots in an area of nebulosity along the northern rim. Pickering's Triangle is much fainter and has no NGC number (though 6979 is occasionally used to refer to it). It

2400-547: Is emitted at this wavelength. An 8-inch (200 mm) telescope equipped with an O-III filter shows the delicate lacework apparent in photographs. Smaller telescopes with an O-III filter can show the nebula as well, and some argue that it can be seen without any optical aid except an O-III filter held up to the eye. The brighter segments of the nebula have the New General Catalogue designations NGC 6960, 6974, 6979, 6992, and 6995. The easiest segment to find

2500-437: Is partially intercepted by the supernova remnant. With an estimated (but uncertain) distance of about 1860 ly away, this star seemed to support the revised estimate of 1760 ly. More recent investigations of the Cygnus Loop's distance using Gaia parallax measurements of several stars seen toward the Cygnus Loop have led to more accurate distance estimates. One of these stars, a 9.6 magnitude B8 star (BD+31 4224) located near

2600-827: Is physically located in Baltimore , Maryland on the Homewood campus of Johns Hopkins University , one of the 39 U.S. universities and seven international affiliates that make up the AURA consortium. STScI was established in 1981 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, provided similar support for European astronomers until 2011, when these activities were moved to

2700-585: The Challenger disaster brought the U.S. space program to a halt, grounded the Shuttle fleet, and forced the launch to be postponed for several years. During this delay the telescope was kept in a clean room, powered up and purged with nitrogen, until a launch could be rescheduled. This costly situation (about US$ 6 million per month) pushed the overall costs of the project higher. However, this delay allowed time for engineers to perform extensive tests, swap out

2800-473: The Einstein Observatory , HEAO 1 , and OSO 7 , respectively. The Cygnus Loop is a strong source of soft X-rays. The center of the supernova shell as determined from X-ray data lies at J1950 RA 20 49 45 Dec +30° 53′. A characteristic thermal temperature averaged over the loop from X-ray spectral data is T x = 2.9 ± 1.5 x 10 K. An X-ray surface brightness map of

2900-508: The first space telescope , but it is one of the largest and most versatile, renowned as a vital research tool and as a public relations boon for astronomy . The Hubble telescope is named after astronomer Edwin Hubble and is one of NASA's Great Observatories . The Space Telescope Science Institute (STScI) selects Hubble's targets and processes the resulting data, while the Goddard Space Flight Center (GSFC) controls

3000-462: The nebula . The analysis of the emissions from the nebula indicates the presence of oxygen , sulfur , and hydrogen . The Cygnus Loop is also a strong emitter of radio waves and x-rays . In modern usage, the names Veil Nebula , Cirrus Nebula , and Filamentary Nebula generally refer to all the visible structure of the remnant, or even to the entire loop itself. The structure is so large that several NGC numbers were assigned to various arcs of

3100-465: The 1991 comedy The Naked Gun 2½: The Smell of Fear , in a scene where historical disasters are displayed, Hubble is pictured with RMS Titanic and LZ 129 Hindenburg . Nonetheless, during the first three years of the Hubble mission, before the optical corrections, the telescope carried out a large number of productive observations of less demanding targets. The error was well characterized and stable, enabling astronomers to partially compensate for

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3200-475: The Cygnus Loop progenitor star's mass at 12 to 15 Solar masses , a value that puts the expected remnant firmly within neutron star boundaries. However, despite many searches, no compact stellar remnant had been confidently identified since the identification of the supernova remnant. A noted anomaly is that in X-rays, the nebula appears perfectly spherical aside from a "blowout region" to the south. Searches for

3300-693: The European Space Astronomy Centre. One complex task that falls to STScI is scheduling observations for the telescope. Hubble is in a low-Earth orbit to enable servicing missions, which results in most astronomical targets being occulted by the Earth for slightly less than half of each orbit. 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

3400-584: The FOS. 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. It could take up to 100,000 measurements per second with a photometric accuracy of about 2% or better. HST's guidance system can also be used as a scientific instrument. Its three Fine Guidance Sensors (FGS) are primarily used to keep

3500-608: The Faint Object Spectrograph (FOS). WF/PC used a radial instrument bay, and the other four instruments were each installed in an axial instrument bay. 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. The instrument contained eight charge-coupled device (CCD) chips divided between two cameras, each using four CCDs. Each CCD has

3600-561: The HST is a Cassegrain reflector of Ritchey–Chrétien design , as are most large professional telescopes. This design, with two hyperbolic mirrors, is known for good imaging performance over a wide field of view, with the disadvantage that the mirrors have shapes that are hard to fabricate and test. The mirror and optical systems of the telescope determine the final performance, and they were designed to exacting specifications. Optical telescopes typically have mirrors polished to an accuracy of about

3700-515: The OTA was not designed with optimum infrared performance in mind—for example, the mirrors are kept at stable (and warm, about 15 °C) temperatures by heaters. This limits Hubble's performance as an infrared telescope. Perkin-Elmer (PE) intended to use custom-built and extremely sophisticated computer-controlled polishing machines to grind the mirror to the required shape. However, in case their cutting-edge technology ran into difficulties, NASA demanded that PE sub-contract to Kodak to construct

3800-425: The Shuttle servicing missions. COSTAR was a corrective optics device rather than a science instrument, but occupied one of the four axial instrument bays. Since the final servicing mission in 2009, the four active instruments have been ACS, COS, STIS and WFC3. NICMOS is kept in hibernation, but may be revived if WFC3 were to fail in the future. Of the former instruments, three (COSTAR, FOS and WFPC2) are displayed in

3900-725: The Smithsonian National Air and Space Museum . The FOC is in the Dornier museum, Germany. The HSP is in the Space Place at the University of Wisconsin–Madison . The first WFPC was dismantled, and some components were then re-used in WFC3. Within weeks of the launch of the telescope, the returned images indicated a serious problem with the optical system. Although the first images appeared to be sharper than those of ground-based telescopes, Hubble failed to achieve

4000-575: The Sun (precluding observations of Mercury ), Moon and Earth. The solar avoidance angle is about 50°, to keep sunlight from illuminating any part of the OTA. Earth and Moon avoidance keeps bright light out of the FGSs, and keeps scattered light from entering the instruments. If the FGSs are turned off, the Moon and Earth can be observed. Earth observations were used very early in the program to generate flat-fields for

4100-547: The Triangle is probably not what Herschel saw or what the Catalogue intended for this entry: it was discovered only photographically, after the Catalogue was published, and long after Herschel's observation. NGC 6974 was reported by Lord Rosse , but the position he gave lies in an empty region inside the main loop. It was assumed that he recorded the position incorrectly, and the New General Catalogue gives Rosse's object as

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4200-415: The U.S. National Academy of Sciences recommended 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 scientific objectives for a large space telescope. Also crucial was the work of Nancy Grace Roman , the "Mother of Hubble". Well before it became an official NASA project, she gave public lectures touting

4300-536: The Veil Nebula has been directly observed. Cygnus Loop The Cygnus Loop (radio source W78, or Sharpless 103 ) is a large supernova remnant (SNR) in the constellation Cygnus , an emission nebula measuring nearly 3° across. Some arcs of the loop, known collectively as the Veil Nebula or Cirrus Nebula, emit in the visible electromagnetic range. Radio, infrared, and X-ray images reveal

4400-745: The WFPC1 instrument. There is a so-called continuous viewing zone (CVZ), within roughly 24° of Hubble's orbital poles , 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. 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. Hubble orbits in low Earth orbit at an altitude of approximately 540 kilometers (340 mi) and an inclination of 28.5°. The position along its orbit changes over time in

4500-596: The actual size of the bubble was about 40% smaller than the conventional value, leading to a distance of about 1470 ly. A larger revised value of 540 pc (1760 ly) appeared to be corroborated by Blair's later discovery, via the Far Ultraviolet Spectroscopic Explorer (FUSE), of a star seemingly behind the Veil. A UV spectrum of this star, KPD 2055+3111 of spectral type sdOB, showed absorption lines in its spectrum indicate that its light

4600-681: The complete loop. The visual portion of the Cygnus Loop is known as the Veil Nebula, also called the Cirrus Nebula or the Filamentary Nebula. Several components have separate names and identifiers, including the "Western Veil" or "Witch's Broom", the "Eastern Veil", and Pickering's Triangle. NGC 6960, the Western Veil , is the western part of the remnant, also known as the "Witch's Broom", located at J2000 RA 20 45 58.1 Dec +30° 35′ 43″. As

4700-618: The construction. The two initial, primary computers on the HST were the 1.25 MHz DF-224 system, built by Rockwell Autonetics, which contained three redundant CPUs, and two redundant NSSC-1 (NASA Standard Spacecraft Computer, Model 1) systems, developed by Westinghouse and GSFC using diode–transistor logic (DTL). A co-processor for the DF-224 was added during Servicing Mission 1 in 1993, which consisted of two redundant strings of an Intel-based 80386 processor with an 80387 math co-processor. The DF-224 and its 386 co-processor were replaced by

4800-472: The daytime. The remnants have since expanded to cover an area of the sky roughly 3 degrees in diameter (about 6 times the diameter, and 36 times the area, of the full Moon). While previous distance estimates have ranged from 1200 to 5800 light-years , a recent determination of 2400 light-years is based on direct astrometric measurements. (The distance estimates affect also the estimates of size and age.) The Hubble Space Telescope captured several images of

4900-498: The defective mirror by using sophisticated image processing techniques such as deconvolution . A commission headed by Lew Allen , director of the Jet Propulsion Laboratory , was established to determine how the error could have arisen. The Allen Commission found that a reflective null corrector , a testing device used to achieve a properly shaped non-spherical mirror, had been incorrectly assembled—one lens

5000-410: The eastern end as "Branching nebulosity ... The following part divides into several streams uniting again towards the south." When finely resolved, some parts of the nebula appear to be rope-like filaments. The standard explanation is that the shock waves are so thin, less than one part in 50,000 of the radius, that the shell is visible only when viewed exactly edge-on, giving the shell the appearance of

5100-573: 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, starting with a blank manufactured by Corning from their ultra-low expansion glass. To keep the mirror's weight to a minimum it consisted of top and bottom plates, each 25 mm (0.98 in) thick, sandwiching a honeycomb lattice. Perkin-Elmer simulated microgravity by supporting

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5200-490: The entire frequency range 25 to 5000 MHz. The southeastern knot is located at J2000 RA 20 56 21.2 Dec +30° 23′ 59″ on the southeastern rim of the Cygnus Loop. The knot has been identified as an encounter between the blast wave from the supernova and a small isolated cloud. The knot is a prominent X-ray feature, consisting of a number of filaments correlated with visual line emission. By combining visual and X-ray data, it can be shown that

5300-501: The first Orbiting Astronomical Observatory (OAO) mission. OAO-1's battery failed after three days, terminating the mission. It was followed by Orbiting Astronomical Observatory 2 (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. The OSO and OAO missions demonstrated the important role space-based observations could play in astronomy. In 1968, NASA developed firm plans for

5400-528: 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. Congress eventually approved funding of US$ 36 million for 1978, and the design of the LST began in earnest, aiming for a launch date of 1983. In 1983,

5500-467: 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. Because of the way the HST's instruments were designed, two different sets of correctors were required. The design of the Wide Field and Planetary Camera 2, already planned to replace

5600-413: The launch date of the telescope to October 1984. The mirror was completed by the end of 1981; it was washed using 9,100 L (2,000 imp gal; 2,400 US gal) of hot, deionized water and then received a reflective coating of 65 nm-thick aluminum and a protective coating of 25 nm-thick magnesium fluoride . Doubts continued to be expressed about Perkin-Elmer's competence on

5700-494: The loop was obtained with a one-dimensional X-ray telescope flown aboard an Aerobee 170 sounding rocket launched on March 30, 1973, from the White Sands Missile Range . Most stars that produce supernovae leave behind compact stellar remnants - a neutron star or black hole , typically depending on the mass of the original star. Various techniques based on the features of the supernova remnant estimate

5800-415: The mirror being ground very precisely but to the wrong shape. During fabrication, a few tests using conventional null correctors correctly reported spherical aberration . But these results were dismissed, thus missing the opportunity to catch the error, because the reflective null corrector was considered more accurate. The commission blamed the failings primarily on Perkin-Elmer. Relations between NASA and

5900-414: The mirror from the back with 130 rods that exerted varying amounts of force. This ensured the mirror's final shape would be correct and to specification when deployed. 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 moved

6000-427: The mirror. 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. Many feared that Hubble would be abandoned. The design of the telescope had always incorporated servicing missions, and astronomers immediately began to seek potential solutions to

6100-499: The most detailed visible light images, allowing a deep view into space. Many Hubble observations have led to breakthroughs in astrophysics , such as determining the rate of expansion of the universe . Space telescopes were proposed as early as 1923, and the Hubble telescope was funded and built in the 1970s by the United States space agency NASA with contributions from the European Space Agency . Its intended launch

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6200-415: The nebula has a relatively bright integrated magnitude of 7, it is spread over so large an area that the surface brightness is quite low, so the nebula is notorious among astronomers as being difficult to see. However, an observer can see the nebula clearly in a telescope using an O-III astronomical filter (isolating the wavelength of light from doubly ionized oxygen ), as almost all light from this nebula

6300-403: The nebula. There are three main visual components: NGC 6974 and NGC 6979 are luminous knots in a fainter patch of nebulosity on the northern rim between NGC 6992 and Pickering's Triangle. The nebula was discovered on 5 September 1784 by William Herschel . He described the western end of the nebula as "Extended; passes thro' 52 Cygni... near 2 degree in length", and described

6400-452: The next hurdle for NASA was to obtain funding for the instrument, which would be far more costly than any Earth-based telescope. The U.S. 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. In 1974, public spending cuts led to Congress deleting all funding for

6500-666: The older 1801 version). The WFPC-1 was replaced by the WFPC-2 during Servicing Mission 1 in 1993, which was then replaced by the Wide Field Camera 3 (WFC3) during Servicing Mission 4 in 2009. The upgrade extended Hubble's capability of seeing deeper into the universe and providing images in three broad regions of the spectrum. 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

6600-411: The optics company had been severely strained during the telescope construction, due to frequent schedule slippage and cost overruns. NASA found that Perkin-Elmer did not review or supervise the mirror construction adequately, did not assign its best optical scientists to the project (as it had for the prototype), and in particular did not involve the optical designers in the construction and verification of

6700-442: The other knot in the northern cloud, located at J2000 RA 20 51 04.3 Dec +31° 49′ 41″, one degree north of Rosse's position. (This position is farther east than NGC 6979, even though NGC objects are generally ordered by increasing RA.) These filaments in the north-central area are sometimes known as the "carrot". The spectrum at 34.5 MHz of the region associated with NGC 6974 ranges straight over

6800-412: The point-like source probably unrelated to the galaxy. Whether the feature is a pulsar wind nebula, and if so whether it is related to the Cygnus Loop, is still unknown for certain. If it is indeed the compact stellar remnant of the supernova, the neutron star would have to have been ejected from the center of the nebula at a speed of roughly 1,850  km/s , depending on the precise age and distance of

6900-425: The problem that could be applied at the first servicing mission, scheduled for 1993. While Kodak had ground a back-up mirror for Hubble, it would have been impossible to replace the mirror in orbit, and too expensive and time-consuming to bring the telescope 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

7000-636: The project. Hubble's cumulative costs are estimated to be about US$ 11.3 billion in 2015 dollars, which include all subsequent servicing costs, but not ongoing operations, making it the most expensive science mission in NASA history. Hubble accommodates five science instruments at a given time, plus the Fine Guidance Sensors , which are mainly used for aiming the telescope but are occasionally used for scientific astrometry measurements. Early instruments were replaced with more advanced ones during

7100-508: The remnant's northwestern rim shows evidence of interactions of its stellar wind with the Cygnus Loop's shock wave, thereby indicating it is located actually inside the remnant. This star's Gaia estimated distance of around 730 pc, along with two other stars both at about 740 pc which exhibit spectral features indicating they must lie behind the remnant, leads to new distance of 725 ± {\displaystyle \pm } 15 pc or around 2400 light-years. The Gaia estimated distance to

7200-493: The remnant's optical filaments to calculate a distance of 770 parsecs or 2500 light-years . However, in 1999, William Blair, assuming that the shock wave should be expanding at the same rate in all directions, compared the angular expansion along the sides of the bubble (visible in Hubble Space Telescope images) with direct line-of-sight measurements of the radial expansion towards the Earth and concluded that

7300-402: The remnant. In the novel Mindbridge by Joe Haldeman , the Cygnus Loop is the remains of the home star of an omnipotent, immortal race that ultimately decided to destroy itself. Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble ) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not

7400-409: 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. 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 as built was −1.01390 ± 0.0002 , instead of

7500-439: The scientific value of the telescope. After it was approved, she became the program scientist, setting up the steering committee in charge of making astronomer needs feasible to implement and writing testimony to Congress throughout the 1970s to advocate continued funding of the telescope. Her work as project scientist helped set the standards for NASA's operation of large scientific projects. Space-based astronomy had begun on

7600-534: The sdOB star KPD 2055+3111 is 819 pc (2,670 ly). This new distance, surprisingly close to the value estimated some 60 years ago by Minkowski, means the Cygnus Loop is physically some 37 pc (120 ly) in diameter and has an age of around 20,000 years. The brightest far-ultraviolet sources of the Cygnus Loop occur in the north-east edge of the remnant. The first flight of the High Resolution Emission Line Spectrometer (HIRELS),

7700-451: The southeastern knot is an indentation on the surface of the blast wave, not a small cloud but the tip of a larger cloud. The presence of a reverse shock is evidence that the knot represents an early stage of a blast wave encountering a large cloud. Until 1999, the most often-quoted distance to the supernova remnant was a 1958 estimate made by R. Minkowski , combining his radial velocity measurements with E. Hubble 's proper motion study of

7800-405: The spacecraft in which the telescope and instruments would be housed proceeded somewhat more smoothly than the construction of the OTA, Lockheed experienced some budget and schedule slippage, and by the summer 1985, construction of the spacecraft was 30% over budget and three months behind schedule. An MSFC report said Lockheed tended to rely on NASA directions rather than take their own initiative in

7900-424: The spacecraft. Hubble features a 2.4 m (7 ft 10 in) mirror, and its five main instruments observe in the ultraviolet , visible , and near-infrared regions of the electromagnetic spectrum . Hubble's orbit outside the distortion of Earth's atmosphere allows it to capture extremely high-resolution images with substantially lower background light than ground-based telescopes. It has recorded some of

8000-826: The spectrum are covered by the Compton Gamma Ray Observatory , the Chandra X-ray Observatory , and the Spitzer Space Telescope (which covers the infrared bands). The mid-IR-to-visible band successor to the Hubble telescope is the James Webb Space Telescope (JWST), which was launched on December 25, 2021, with the Nancy Grace Roman Space Telescope due to follow in 2027. In 1923, Hermann Oberth —considered

8100-468: The technology to allow this was soon to become available. The continuing success of the OAO program encouraged increasingly strong consensus within the astronomical community that the LST should be a major goal. 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,

8200-560: The telescope accurately pointed during an observation, but can also be used to carry out extremely accurate astrometry ; measurements accurate to within 0.0003 arcseconds have been achieved. The Space Telescope Science Institute (STScI) is responsible for the scientific operation of the telescope and the delivery of data products to astronomers. STScI is operated by the Association of Universities for Research in Astronomy (AURA) and

8300-418: The telescope project. In 1977, then NASA Administrator James C. Fletcher proposed a token $ 5 million for Hubble in NASA's budget. Then NASA Associate Administrator for Space Science, Noel Hinners , instead cut all funding for Hubble, gambling that this would galvanize the scientific community into fighting for full funding. As Hinners recalls: It was clear that year that we weren't going to be able to get

8400-422: The telescope was named after Edwin Hubble , who confirmed one of the greatest scientific discoveries of the 20th century, made by Georges Lemaître , that the universe is expanding . Once the Space Telescope project had been given the go-ahead, work on the program was divided among many institutions. Marshall Space Flight Center (MSFC) was given responsibility for the design, development, and construction of

8500-575: The telescope, including all five of the main instruments. The fifth mission was initially canceled on safety grounds following the Columbia disaster (2003), but after NASA administrator Michael D. Griffin approved it, the servicing mission was completed in 2009. Hubble completed 30 years of operation in April 2020 and is predicted to last until 2030 to 2040. Hubble is the visible light telescope in NASA's Great Observatories program ; other parts of

8600-436: The telescope, while Goddard Space Flight Center was given overall control of the scientific instruments and ground-control center for the mission. MSFC commissioned the optics company Perkin-Elmer to design and build the optical telescope assembly (OTA) and Fine Guidance Sensors for the space telescope. Lockheed was commissioned to construct and integrate the spacecraft in which the telescope would be housed. Optically,

8700-501: The telescope. 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. Within the shell, a graphite-epoxy frame keeps the working parts of the telescope firmly aligned. Because graphite composites are hygroscopic , there was a risk that water vapor absorbed by the truss while in Lockheed's clean room would later be expressed in

8800-436: The troops. So I advocated that we not put anything in. I don't remember any of the detailed discussions or whether there were any, but Jim went along with that so we zeroed it out. It had, from my perspective, the desired impact of stimulating the astronomy community to renew their efforts on the lobbying front. While I like to think in hindsight it was a brilliant political move, I'm not sure I thought it through all that well. It

8900-455: The two main advantages that a space-based observatory would have over ground-based telescopes. First, the angular resolution (the 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, known to astronomers as seeing . At that time ground-based telescopes were limited to resolutions of 0.5–1.0 arcseconds , compared to

9000-409: The usefulness of the telescope for faint objects or high-contrast imaging. This meant nearly all the cosmological programs were essentially impossible, since they required observation of exceptionally faint objects. This led politicians to question NASA's competence, scientists to rue the cost which could have gone to more productive endeavors, and comedians to make jokes about NASA and the telescope. In

9100-535: The vacuum of space; resulting in the telescope's instruments being covered by ice. To reduce that risk, a nitrogen gas purge was performed before launching the telescope into space. As well as electrical power systems, the Pointing Control System controls HST orientation using five types of sensors (magnetic sensors, optical sensors, and six gyroscopes) and two types of actuators ( reaction wheels and magnetic torquers ). While construction of

9200-747: The westernmost NGC object in the nebula (first in right ascension ), its number is sometimes used as an NGC identifier for the nebula as a whole. These three luminous areas make up the Eastern Veil . NGC 6992 is an HI shell located along the north-eastern edge of the loop at J2000 RA 20 56 19.0 Dec +31° 44′ 34″. NGC 6995 is located farther south at J2000 RA 20 57 10.7 Dec +31° 14′ 07″, and IC 1340 even farther south at J2000 RA 20 56 12.0 Dec +31° 04′ 00″. Also known as Pickering's Wedge, or Pickering's Triangular Wisp, this segment of relatively faint nebulosity

9300-406: The wrong shape. Although it was believed to be one of the most precisely figured optical mirrors ever made, smooth to about 10 nanometers, the outer perimeter was too flat by about 2200 nanometers (about 1 ⁄ 450 mm or 1 ⁄ 11000 inch). This difference was catastrophic, introducing severe spherical aberration, a flaw in which light reflecting off the edge of a mirror focuses on

9400-480: Was discovered photographically in 1904 by Williamina Fleming (after the New General Catalogue was published), but credit went to Edward Charles Pickering , the director of her observatory, as was the custom of the day. The Veil Nebula is expanding at a velocity of about 1.5 million kilometers per hour. Using images taken by the Hubble Space Telescope between 1997 and 2015, the expansion of

9500-490: Was discovered photographically in 1904 by Williamina Fleming at Harvard Observatory, where Edward Charles Pickering was director at the time. The Triangle is brightest along the northern side of the loop, though photographs show the nebulosity extending into the central area as well. These two objects are generally identified today (as by the NGC/IC Project and Uranometria ) with two brighter knots of nebulosity in

9600-534: Was due to be observed. Engineering support for HST is provided by NASA and contractor personnel at the Goddard Space Flight Center in Greenbelt, Maryland , 48 km (30 mi) south of the STScI. Hubble's operation is monitored 24 hours per day by four teams of flight controllers who make up Hubble's Flight Operations Team. By January 1986, the planned launch date for Hubble that October looked feasible, but

9700-480: Was forced to postpone the launch date until 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 withstand frequent passages from direct sunlight into the darkness of Earth's shadow , which would cause major changes in temperature, while being stable enough to allow extremely accurate pointing of

9800-529: Was in 1983, but the project was beset by technical delays, budget problems, and the 1986 Challenger disaster . Hubble was finally launched in 1990, but its main mirror had been ground incorrectly, resulting in spherical aberration that compromised the telescope's capabilities. The optics were corrected to their intended quality by a servicing mission in 1993. Hubble is the only telescope designed to be maintained in space by astronauts. Five Space Shuttle missions have repaired, upgraded, and replaced systems on

9900-414: Was out of position by 1.3 mm (0.051 in). During the initial grinding and polishing of the mirror, Perkin-Elmer analyzed its surface with two conventional refractive null correctors. However, for the final manufacturing step ( figuring ), they switched to the custom-built reflective null corrector, designed explicitly to meet very strict tolerances. The incorrect assembly of this device resulted in

10000-510: Was something that was spur of the moment. [...] $ 5 million would let them think that all is well anyway, but it's not. So let's give them a message. My own thinking, get them stimulated to get into action. Zeroing it out would certainly give that message. I think it was as simple as that. Didn't talk to anybody else about doing it first, just, "Let's go do that". Voila, it worked. Don't know whether I'd do that again. The political ploy worked. In response to Hubble being zeroed out of NASA's budget,

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