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38-459: Asteroids are discovered by telescopes which repeatedly survey large areas of sky . Efforts which concentrate on discovering NEOs are considered part of the "Spaceguard Survey," regardless of which organization they are affiliated with. A number of organizations have also raised related discussions and proposals on asteroid-impact avoidance . Arthur C. Clarke coined the term in his novel Rendezvous with Rama (1973) where "Project Spaceguard"

76-544: A few bands can be observed from the Earth's surface. These bands are visible – near-infrared and a portion of the radio-wave part of the spectrum. For this reason there are no X-ray or far-infrared ground-based telescopes as these have to be observed from orbit. Even if a wavelength is observable from the ground, it might still be advantageous to place a telescope on a satellite due to issues such as clouds, astronomical seeing and light pollution . The disadvantages of launching

114-504: A focal point. Optical telescopes are used for astronomy and in many non-astronomical instruments, including: theodolites (including transits ), spotting scopes , monoculars , binoculars , camera lenses , and spyglasses . There are three main optical types: A Fresnel imager is a proposed ultra-lightweight design for a space telescope that uses a Fresnel lens to focus light. Beyond these basic optical types there are many sub-types of varying optical design classified by

152-419: A mirror instead of a lens was being investigated soon after the invention of the refracting telescope. The potential advantages of using parabolic mirrors —reduction of spherical aberration and no chromatic aberration —led to many proposed designs and several attempts to build reflecting telescopes . In 1668, Isaac Newton built the first practical reflecting telescope, of a design which now bears his name,

190-475: A single receiver and records a single time-varying signal characteristic of the observed region; this signal may be sampled at various frequencies. In some newer radio telescope designs, a single dish contains an array of several receivers; this is known as a focal-plane array . By collecting and correlating signals simultaneously received by several dishes, high-resolution images can be computed. Such multi-dish arrays are known as astronomical interferometers and

228-625: A space telescope include cost, size, maintainability and upgradability. Some examples of space telescopes from NASA are the Hubble Space Telescope that detects visible light, ultraviolet, and near-infrared wavelengths, the Spitzer Space Telescope that detects infrared radiation, and the Kepler Space Telescope that discovered thousands of exoplanets. The latest telescope that was launched was

266-477: A telescope was a 1608 patent submitted to the government in the Netherlands by Middelburg spectacle maker Hans Lipperhey for a refracting telescope . The actual inventor is unknown but word of it spread through Europe. Galileo heard about it and, in 1609, built his own version, and made his telescopic observations of celestial objects. The idea that the objective , or light-gathering element, could be

304-412: Is called an observatory . Radio telescopes are directional radio antennas that typically employ a large dish to collect radio waves. The dishes are sometimes constructed of a conductive wire mesh whose openings are smaller than the wavelength being observed. Unlike an optical telescope, which produces a magnified image of the patch of sky being observed, a traditional radio telescope dish contains

342-583: Is in contrast to other surveys which focus on finding much larger (greater than 100 m) objects years to decades before any potential impacts, at times when they could potentially still be deflected away from Earth. Another short-term warning system is the NASA Scout program that came into operation in 2016. On October 19, 2017, one of the Survey telescopes, Pan-STARRS 1, discovered the first interstellar asteroid, 'Oumuamua . The United Kingdom also hosts

380-528: Is now also being applied to optical telescopes using optical interferometers (arrays of optical telescopes) and aperture masking interferometry at single reflecting telescopes. Radio telescopes are also used to collect microwave radiation , which has the advantage of being able to pass through the atmosphere and interstellar gas and dust clouds. Some radio telescopes such as the Allen Telescope Array are used by programs such as SETI and

418-471: Is often referred to as the "Spaceguard Goal." A number of efforts which receive money through NASA are all considered to be working on the "Spaceguard Project." The effect of the impact of Comet Shoemaker–Levy 9 to Jupiter in July 1994 created a greater perception of importance to the detection of near Earth objects. As David Levy stated in an interview "The giggle factor disappeared after Shoemaker-Levy 9." He

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456-482: Is possible to make very tiny antenna). The near-infrared can be collected much like visible light; however, in the far-infrared and submillimetre range, telescopes can operate more like a radio telescope. For example, the James Clerk Maxwell Telescope observes from wavelengths from 3 μm (0.003 mm) to 2000 μm (2 mm), but uses a parabolic aluminum antenna. On the other hand,

494-406: Is underway on several 30–40m designs. The 20th century also saw the development of telescopes that worked in a wide range of wavelengths from radio to gamma-rays . The first purpose-built radio telescope went into operation in 1937. Since then, a large variety of complex astronomical instruments have been developed. Since the atmosphere is opaque for most of the electromagnetic spectrum, only

532-645: The Arecibo Observatory to search for extraterrestrial life. An optical telescope gathers and focuses light mainly from the visible part of the electromagnetic spectrum. Optical telescopes increase the apparent angular size of distant objects as well as their apparent brightness . For the image to be observed, photographed, studied, and sent to a computer, telescopes work by employing one or more curved optical elements, usually made from glass lenses and/or mirrors , to gather light and other electromagnetic radiation to bring that light or radiation to

570-822: The Earth's atmosphere is opaque to this part of the electromagnetic spectrum. An example of this type of telescope is the Fermi Gamma-ray Space Telescope which was launched in June 2008. The detection of very high energy gamma rays, with shorter wavelength and higher frequency than regular gamma rays, requires further specialization. Such detections can be made either with the Imaging Atmospheric Cherenkov Telescopes (IACTs) or with Water Cherenkov Detectors (WCDs). Examples of IACTs are H.E.S.S. and VERITAS with

608-405: The Netherlands at the beginning of the 17th century. They were used for both terrestrial applications and astronomy . The reflecting telescope , which uses mirrors to collect and focus light, was invented within a few decades of the first refracting telescope. In the 20th century, many new types of telescopes were invented, including radio telescopes in the 1930s and infrared telescopes in

646-504: The Newtonian reflector . The invention of the achromatic lens in 1733 partially corrected color aberrations present in the simple lens and enabled the construction of shorter, more functional refracting telescopes. Reflecting telescopes, though not limited by the color problems seen in refractors, were hampered by the use of fast tarnishing speculum metal mirrors employed during the 18th and early 19th century—a problem alleviated by

684-572: The Spitzer Space Telescope , observing from about 3 μm (0.003 mm) to 180 μm (0.18 mm) uses a mirror (reflecting optics). Also using reflecting optics, the Hubble Space Telescope with Wide Field Camera 3 can observe in the frequency range from about 0.2 μm (0.0002 mm) to 1.7 μm (0.0017 mm) (from ultra-violet to infrared light). With photons of the shorter wavelengths, with

722-764: The 1960s. The word telescope was coined in 1611 by the Greek mathematician Giovanni Demisiani for one of Galileo Galilei 's instruments presented at a banquet at the Accademia dei Lincei . In the Starry Messenger , Galileo had used the Latin term perspicillum . The root of the word is from the Ancient Greek τῆλε, romanized tele 'far' and σκοπεῖν, skopein 'to look or see'; τηλεσκόπος, teleskopos 'far-seeing'. The earliest existing record of

760-576: The Earth the next day. New survey projects, such as the Asteroid Terrestrial-impact Last Alert System (ATLAS) program operated by the University of Hawaii , aim to greatly increase the number of small (down to approximately 10 m) impactors that are discovered before atmospheric entry —typically with days to weeks of warning, enabling evacuations of the affected areas and damage mitigation planning. This

798-627: The James Webb Space Telescope on December 25, 2021, in Kourou, French Guiana. The Webb telescope detects infrared light. The name "telescope" covers a wide range of instruments. Most detect electromagnetic radiation , but there are major differences in how astronomers must go about collecting light (electromagnetic radiation) in different frequency bands. As wavelengths become longer, it becomes easier to use antenna technology to interact with electromagnetic radiation (although it

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836-406: The books already, that would take a year ... I mean a typical small mission ... takes four years from approval to start to launch ... Lack of a master plan and dangers of false alarms have been pointed out by Stefan Lövgren. Telescope A telescope is a device used to observe distant objects by their emission, absorption , or reflection of electromagnetic radiation . Originally, it

874-456: The development of systems for surveying abundances in comets as well as techniques for determining the sizes of cometary nuclei which uses optical and infrared measurements. His studies focused on comets as well as asteroids and he also supervises numerous graduate students. He was an elected fellow of the AAAS . He authored over 100 papers published in journals and was also an avid sailor who had

912-682: The higher frequencies, glancing-incident optics, rather than fully reflecting optics are used. Telescopes such as TRACE and SOHO use special mirrors to reflect extreme ultraviolet , producing higher resolution and brighter images than are otherwise possible. A larger aperture does not just mean that more light is collected, it also enables a finer angular resolution. Telescopes may also be classified by location: ground telescope, space telescope , or flying telescope . They may also be classified by whether they are operated by professional astronomers or amateur astronomers . A vehicle or permanent campus containing one or more telescopes or other instruments

950-671: The impact of Comet Shoemaker-Levy 9, asteroid detection programs all over the world received greater funding. The Working Group on Near-Earth Objects (WGNEO) of the International Astronomical Union held a workshop in 1995 entitled Beginning the Spaceguard Survey which led to an international organization called the Spaceguard Foundation . Subsequently, there have been Spaceguard associations or foundations formed in countries around

988-415: The introduction of silver coated glass mirrors in 1857, and aluminized mirrors in 1932. The maximum physical size limit for refracting telescopes is about 1 meter (39 inches), dictating that the vast majority of large optical researching telescopes built since the turn of the 20th century have been reflectors. The largest reflecting telescopes currently have objectives larger than 10 meters (33 feet), and work

1026-558: The mandate of reducing the minimum size at which more than 90% of near-Earth asteroids are known to 140 m. The 2002 Eastern Mediterranean event and the Chelyabinsk meteor (Russia, February 2013) were not detected in advance by any Spaceguard effort. On October 6, 2008, the 4-meter 2008 TC 3 meteoroid was detected by the Catalina Sky Survey (CSS) 1.5 meter telescope at Mount Lemmon , and monitored until it hit

1064-609: The next-generation gamma-ray telescope, the Cherenkov Telescope Array ( CTA ), currently under construction. HAWC and LHAASO are examples of gamma-ray detectors based on the Water Cherenkov Detectors. A discovery in 2012 may allow focusing gamma-ray telescopes. At photon energies greater than 700 keV, the index of refraction starts to increase again. Michael A%27Hearn Michael Francis A'Hearn (November 17, 1940 – May 29, 2017)

1102-624: The rays just a few degrees . The mirrors are usually a section of a rotated parabola and a hyperbola , or ellipse . In 1952, Hans Wolter outlined 3 ways a telescope could be built using only this kind of mirror. Examples of space observatories using this type of telescope are the Einstein Observatory , ROSAT , and the Chandra X-ray Observatory . In 2012 the NuSTAR X-ray Telescope

1140-479: The self-styled Spaceguard Centre which conducts astrometric research (MPC code J26) and is open to the general public daily, but it is not affiliated with or supported by any public body. According to Dr. Michael F. A'Hearn , a typical mission would take too long from approval to launch if there was an emergency: REP. STEWART: ... are we technologically capable of launching something that could intercept [an asteroid]? ... DR. A'HEARN: No. If we had spacecraft plans on

1178-511: The task they perform such as astrographs , comet seekers and solar telescopes . Most ultraviolet light is absorbed by the Earth's atmosphere, so observations at these wavelengths must be performed from the upper atmosphere or from space. X-rays are much harder to collect and focus than electromagnetic radiation of longer wavelengths. X-ray telescopes can use X-ray optics , such as Wolter telescopes composed of ring-shaped 'glancing' mirrors made of heavy metals that are able to reflect

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1216-519: The technique is called aperture synthesis . The 'virtual' apertures of these arrays are similar in size to the distance between the telescopes. As of 2005, the record array size is many times the diameter of the Earth – using space-based very-long-baseline interferometry (VLBI) telescopes such as the Japanese HALCA (Highly Advanced Laboratory for Communications and Astronomy) VSOP (VLBI Space Observatory Program) satellite. Aperture synthesis

1254-515: The world to support the ideas of discovering and studying near-Earth objects. Generally, the Spaceguard organizations formed within individual countries are associated with the international foundation or with the NASA efforts only by name, common interests, and similar goals. The initial Spaceguard Goal was achieved, although in slightly longer than 10 years. An extension to the project gave NASA

1292-439: Was an optical instrument using lenses , curved mirrors , or a combination of both to observe distant objects – an optical telescope . Nowadays, the word "telescope" is defined as a wide range of instruments capable of detecting different regions of the electromagnetic spectrum , and in some cases other types of detectors. The first known practical telescopes were refracting telescopes with glass lenses and were invented in

1330-548: Was an American astronomer and astronomy professor at the University of Maryland College of Computer, Mathematical, and Natural Sciences . He was also the principal investigator for NASA 's EPOXI mission. He received his B.A. in science at Boston College and his Ph.D. in Astronomy at the University of Wisconsin–Madison . He was the principal investigator for the NASA Deep Impact mission. He aided in

1368-447: Was launched which uses Wolter telescope design optics at the end of a long deployable mast to enable photon energies of 79 keV. Higher energy X-ray and gamma ray telescopes refrain from focusing completely and use coded aperture masks: the patterns of the shadow the mask creates can be reconstructed to form an image. X-ray and Gamma-ray telescopes are usually installed on high-flying balloons or Earth-orbiting satellites since

1406-429: Was referring to the contemporary attitude that extinction level events were so improbable that those advocating for research for detection and possible deflection methods were only paranoid alarmists. The impact of one of its fragments created a giant dark spot on Jupiter over 12,000 km across, and was estimated to have released an energy equivalent to 6 teratons of TNT (600 times the world's nuclear arsenal). After

1444-479: Was the name of an early warning system created following a fictional catastrophic asteroid impact . This name was later adopted by a number of real life efforts to discover and study near- Earth objects. The name was used for the Survey "with the permission and encouragement of Clarke." A 1992 US Congressional study produced a "Spaceguard Survey Report" which led to a mandate that NASA locate 90% of near-Earth asteroids larger than 1 km within 10 years. This

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