An impact event is a collision between astronomical objects causing measurable effects. Impact events have physical consequences and have been found to occur in planetary systems, though the most frequent involve asteroids, comets or meteoroids and have minimal effect; when large objects impact terrestrial planets such as the Earth, there can be significant physical and biospheric consequences, though atmospheres mitigate many surface impacts through atmospheric entry. Impact craters and structures are dominant landforms on many of the Solar System's solid objects and present the strongest empirical evidence for their frequency and scale. Impact events appear to have played a significant role in the evolution of the Solar System since its formation. Major impact events have shaped Earth's history, have been implicated in the formation of the Earth–Moon system, the evolutionary history of life, the origin of water on Earth and several mass extinctions; the famous prehistoric Chicxulub impact, 66 million years ago, is believed to be the cause of the Cretaceous–Paleogene extinction event.
Throughout recorded history, hundreds of Earth impacts have been reported, with some occurrences causing deaths, property damage, or other significant localised consequences. One of the best-known recorded events in modern times was the Tunguska event, which occurred in Siberia, Russia, in 1908; the 2013 Chelyabinsk meteor event is the only known such incident in modern times to result in a large number of injuries, excluding the 1490 Ch'ing-yang event in China. The Chelyabinsk meteor is the largest recorded object to have encountered the Earth since the Tunguska event; the Comet Shoemaker–Levy 9 impact provided the first direct observation of an extraterrestrial collision of Solar System objects, when the comet broke apart and collided with Jupiter in July 1994. An extrasolar impact was observed in 2013, when a massive terrestrial planet impact was detected around the star ID8 in the star cluster NGC 2547 by NASA's Spitzer space telescope and confirmed by ground observations. Impact events have been a background element in science fiction.
In April 2018, the B612 Foundation reported "It’s 100 per cent certain we’ll be hit, but we’re not 100 per cent certain when." In 2018, physicist Stephen Hawking, in his final book Brief Answers to the Big Questions, considered an asteroid collision to be the biggest threat to the planet. In June 2018, the US National Science and Technology Council warned that America is unprepared for an asteroid impact event, has developed and released the "National Near-Earth Object Preparedness Strategy Action Plan" to better prepare. According to expert testimony in the United States Congress in 2013, NASA would require at least five years of preparation before a mission to intercept an asteroid could be launched. Major impact events have shaped Earth's history, having been implicated in the formation of the Earth–Moon system, the evolutionary history of life, the origin of water on Earth, several mass extinctions. Impact structures are the result of impact events on solid objects and, as the dominant landforms on many of the System's solid objects, present the most solid evidence of prehistoric events.
Notable impact events include the Late Heavy Bombardment, which occurred early in history of the Earth–Moon system, the Chicxulub impact, 66 million years ago, believed to be the cause of the Cretaceous–Paleogene extinction event. Small objects collide with Earth. There is an inverse relationship between the frequency of such events; the lunar cratering record shows that the frequency of impacts decreases as the cube of the resulting crater's diameter, on average proportional to the diameter of the impactor. Asteroids with a 1 km diameter strike Earth every 500,000 years on average. Large collisions – with 5 km objects – happen once every twenty million years; the last known impact of an object of 10 km or more in diameter was at the Cretaceous–Paleogene extinction event 66 million years ago. The energy released by an impactor depends on diameter, density and angle; the diameter of most near-Earth asteroids that have not been studied by radar or infrared can only be estimated within about a factor of two based on the asteroid brightness.
The density is assumed because the diameter and mass are generally estimates. Due to Earth's escape velocity, the minimum impact velocity is 11 km/s with asteroid impacts averaging around 17 km/s on the Earth; the most probable impact angle is 45 degrees. Impact conditions such as asteroid size and speed, but density and impact angle determine the kinetic energy released in an impact event; the more energy is released, the more damage is to occur on the ground due to the environmental effects triggered by the impact. Such effects can be shock waves, heat radiation, the formation of craters with associated earthquakes, tsunamis if water bodies are hit. Human populations are vulnerable to these effects. Large seiche waves arising from earthquakes and large-scale deposit of debris can occur within minutes of impact, thousands of kilometres from impact. Stony asteroids with a diameter of 4 meters enter Earth's atmosphere once per year. Asteroids with a diameter of 7 meters enter the atmosphere about every 5 years with as much kinetic energy as the atomic bomb dropped on Hiroshima, but the air burst is reduced to just 5 kilotons.
These ordinarily explode in the upper atmosphere and most or all of the solids are vaporized. However, asteroids with a diameter of 20 m, which st
Tempel 1 is a periodic Jupiter-family comet discovered by Wilhelm Tempel in 1867. It completes an orbit of the Sun every 5.5 years. Tempel 1 was the target of the Deep Impact space mission, which photographed a deliberate high-speed impact upon the comet in 2005, it was re-visited by the Stardust spacecraft on February 14, 2011 and came back to perihelion in August 2016. Tempel 1 was discovered on April 1867, by Wilhelm Tempel, an astronomer working in Marseille. At the time of discovery, it approached perihelion once every 5.68 years. It was subsequently observed in 1873 and in 1879. Photographic attempts during 1898 and 1905 failed to recover the comet, astronomers surmised that it had disintegrated. In fact, its orbit had changed. Tempel 1's orbit brings it sufficiently close to Jupiter to be altered, with a consequent change in the comet's orbital period; this occurred in 1881. Perihelion changed, increasing by 50 million kilometres, rendering the comet far less visible from Earth. Tempel 1 was rediscovered 13 orbits in 1967, after British astronomer Brian G. Marsden performed precise calculations of the comet's orbit that took into account Jupiter's perturbations.
Marsden found that further close approaches to Jupiter in 1941 and 1953 had decreased both the perihelion distance and the orbital period to values smaller than when the comet was discovered. These approaches moved Tempel 1 into its present libration around the 1:2 resonance with Jupiter. Despite an unfavorable 1967 return, Elizabeth Roemer of the Catalina Observatory took several photographs. Initial inspection revealed nothing, but in late 1968 she found a June 8, 1967 exposure that held the image of an 18th magnitude diffuse object close to where Marsden had predicted the comet to be. At least two images are required for orbit computation, so the next return had to be awaited. Roemer and L. M. Vaughn recovered the comet on January 1972, from Steward Observatory; the comet became observed, reached a maximum brightness of magnitude 11 during May, was last seen on July 10. Since that time the comet has been seen at every apparition, in 1978, 1983, 1989, 1994, 2000 and 2005, its orbital period is 5.515 years.
Tempel 1 is not a bright comet. Its nucleus measures 7.6 km × 4.9 km. Measurements taken by the Hubble Space Telescope in visible light and the Spitzer Space Telescope in infrared light suggest a low albedo of only 4%. A two-day rotation rate was determined. On 4 July 2005 at 05:52 UTC, Tempel 1 was deliberately struck by one component of the NASA Deep Impact probe, one day before perihelion; the impact was photographed by the other component of the probe, which recorded a bright spray from the impact site. The impact was observed by earthbound and space telescopes, which recorded a brightening of several magnitudes; the crater that formed was not visible to Deep Impact due to the cloud of dust raised by the impact, but was estimated to be between 100 and 250 meters in diameter and 30 meters deep. The probe's spectrometer instrument detected dust particles finer than human hair, discovered the presence of silicates, smectite, metal sulfides, amorphous carbon and polycyclic aromatic hydrocarbons.
Water ice was detected in the ejecta. The water ice came from 1 meter below the surface crust. In part because the crater formed during the Deep Impact collision could not be imaged during the initial flyby, on 3 July 2007, NASA approved the New Exploration of Tempel 1 mission; the low-cost mission utilized the existing Stardust spacecraft, which had studied Comet Wild 2 in 2004. Stardust was placed into a new orbit so that it approached Tempel 1, it passed at a distance of 181 km on February 15, 2011, 04:42 UTC. This was the first time. On February 15, NASA scientists identified; the crater is estimated to be 150 m in diameter, has a bright mound in the center created when material from the impact fell back into the crater. Energy of impactor According to NASA "The impactor delivers 19 Gigajoules of kinetic energy to excavate the crater; this kinetic energy is generated by the combination of the mass of the impactor and its velocity when it impacts". According to NASA, Expected crater dimensions "The energy from the impact will excavate a crater 100m wide and 28m deep".
The geometry of the flyby allowed investigators to obtain more three-dimensional information about the nucleus from stereo pairs of images than during Deep Impact's encounter. Scientists were able to spot locations where an elevated flow-like formation of icy material on the comet's surface receded due to sublimation between encounters. Comets are in unstable orbits that outgassing. Tempel 1 passed within 0.04 AU - or 5.9 million km - of the dwarf planet Ceres on November 11, 2011. As a Jupiter-family comet, it will spend years interacting with the giant planet Jupiter passing within 0.02 AU - or 3.0 million km - of Mars on October 17, 218
The National Aeronautics and Space Administration is an independent agency of the United States Federal Government responsible for the civilian space program, as well as aeronautics and aerospace research. NASA was established in 1958; the new agency was to have a distinctly civilian orientation, encouraging peaceful applications in space science. Since its establishment, most US space exploration efforts have been led by NASA, including the Apollo Moon landing missions, the Skylab space station, the Space Shuttle. NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle, the Space Launch System and Commercial Crew vehicles; the agency is responsible for the Launch Services Program which provides oversight of launch operations and countdown management for unmanned NASA launches. NASA science is focused on better understanding Earth through the Earth Observing System. From 1946, the National Advisory Committee for Aeronautics had been experimenting with rocket planes such as the supersonic Bell X-1.
In the early 1950s, there was challenge to launch an artificial satellite for the International Geophysical Year. An effort for this was the American Project Vanguard. After the Soviet launch of the world's first artificial satellite on October 4, 1957, the attention of the United States turned toward its own fledgling space efforts; the US Congress, alarmed by the perceived threat to national security and technological leadership, urged immediate and swift action. On January 12, 1958, NACA organized a "Special Committee on Space Technology", headed by Guyford Stever. On January 14, 1958, NACA Director Hugh Dryden published "A National Research Program for Space Technology" stating: It is of great urgency and importance to our country both from consideration of our prestige as a nation as well as military necessity that this challenge be met by an energetic program of research and development for the conquest of space... It is accordingly proposed that the scientific research be the responsibility of a national civilian agency...
NACA is capable, by rapid extension and expansion of its effort, of providing leadership in space technology. While this new federal agency would conduct all non-military space activity, the Advanced Research Projects Agency was created in February 1958 to develop space technology for military application. On July 29, 1958, Eisenhower signed the National Aeronautics and Space Act, establishing NASA; when it began operations on October 1, 1958, NASA absorbed the 43-year-old NACA intact. A NASA seal was approved by President Eisenhower in 1959. Elements of the Army Ballistic Missile Agency and the United States Naval Research Laboratory were incorporated into NASA. A significant contributor to NASA's entry into the Space Race with the Soviet Union was the technology from the German rocket program led by Wernher von Braun, now working for the Army Ballistic Missile Agency, which in turn incorporated the technology of American scientist Robert Goddard's earlier works. Earlier research efforts within the US Air Force and many of ARPA's early space programs were transferred to NASA.
In December 1958, NASA gained control of the Jet Propulsion Laboratory, a contractor facility operated by the California Institute of Technology. The agency's leader, NASA's administrator, is nominated by the President of the United States subject to approval of the US Senate, reports to him or her and serves as senior space science advisor. Though space exploration is ostensibly non-partisan, the appointee is associated with the President's political party, a new administrator is chosen when the Presidency changes parties; the only exceptions to this have been: Democrat Thomas O. Paine, acting administrator under Democrat Lyndon B. Johnson, stayed on while Republican Richard Nixon tried but failed to get one of his own choices to accept the job. Paine was confirmed by the Senate in March 1969 and served through September 1970. Republican James C. Fletcher, appointed by Nixon and confirmed in April 1971, stayed through May 1977 into the term of Democrat Jimmy Carter. Daniel Goldin was appointed by Republican George H. W. Bush and stayed through the entire administration of Democrat Bill Clinton.
Robert M. Lightfoot, Jr. associate administrator under Democrat Barack Obama, was kept on as acting administrator by Republican Donald Trump until Trump's own choice Jim Bridenstine, was confirmed in April 2018. Though the agency is independent, the survival or discontinuation of projects can depend directly on the will of the President; the first administrator was Dr. T. Keith Glennan appointed by Republican President Dwight D. Eisenhower. During his term he brought together the disparate projects in American space development research; the second administrator, James E. Webb, appointed by President John F. Kennedy, was a Democrat who first publicly served under President Harry S. Truman. In order to implement the Apollo program to achieve Kennedy's Moon la
5535 Annefrank, provisional designation 1942 EM, is a stony Florian asteroid and suspected contact binary from the inner asteroid belt 4.5 kilometers in diameter. It was used as a target to practice the flyby technique that the Stardust space probe would use on the comet Wild 2; the asteroid was discovered 23 March 1942, by German astronomer Karl Reinmuth at Heidelberg Observatory in southwest Germany. It was named after a victim of the Holocaust. Annefrank is a member of the Flora family, one of the largest collisional populations of stony asteroids in the main-belt, it orbits the Sun in the inner main-belt at a distance of 2.1–2.4 AU once every 3 years and 3 months. Its orbit has an inclination of 4 ° with respect to the ecliptic; the body's observation arc begins at Crimea–Nauchnij in 1978, with its identification as 1978 EK6, 36 years after its official discovery observation at Heidelberg. Annefrank has been characterized as a common S-type asteroid. On 2 November 2002, the Stardust space probe flew past Annefrank at a distance of 3079 km.
Its images show the asteroid to be 6.6 × 5.0 × 3.4 km, twice as big as thought, its main body shaped like a triangular prism with several visible impact craters. From the photographs, the albedo of Annefrank was computed to be between 0.18 and 0.24. Preliminary analysis of the Stardust imagery suggests that Annefrank may be a contact binary, although other possible explanations exist for its observed shape. In October 2006, ground-based photometric observations were used in an attempt to measure Annefrank's rotational period. Analysis of the ambiguous lightcurve gave a period of 15.12 hours and a brightness variation of 0.25 magnitude with two alternative period solutions of 12 and 22.8 hours, respectively. In January 2014, photometric observations at the Palomar Transient Factory gave a rotation period of 15.156 and 21.33 hours with an amplitude of 0.17 and 0.20 magnitude, respectively. The lightcurve data suggests that Annefrank is not Lambertian, meaning that surface features, such as shadows from boulders and craters, play a role in the object's perceived brightness and not just the asteroid's relative size when seen from that orientation.
The body's shortest axis is aligned perpendicular to its orbital plane. This minor planet was named after Anne Frank, the Dutch-Jewish diarist who died in a Nazi concentration camp; the official naming citation was published by the Minor Planet Center on 14 May 1995. A page with images from the Stardust flyby Ted Stryk's Stardust page, including enhanced images of 5535 Annefrank Asteroid Lightcurve Database, query form Dictionary of Minor Planet Names, Google books Asteroids and comets rotation curves, CdR – Observatoire de Genève, Raoul Behrend Discovery Circumstances: Numbered Minor Planets - – Minor Planet Center 5535 Annefrank at the JPL Small-Body Database Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters
The coma is the nebulous envelope around the nucleus of a comet, formed when the comet passes close to the Sun on its elliptical orbit. This distinguishes it from stars; the word coma comes from the Greek "kome", which means "hair" and is the origin of the word comet itself. The coma is made of ice and comet dust. Water dominates up to 90% of the volatiles that outflow from the nucleus when the comet is within 3-4 AU of the Sun; the H2O parent molecule is destroyed through photodissociation and to a much smaller extent photoionization. The solar wind plays a minor role in the destruction of water compared to photochemistry. Larger dust particles are left along the comet's orbital path while smaller particles are pushed away from the Sun into the comet's tail by light pressure. On 11 August 2014, astronomers released studies, using the Atacama Large Millimeter/Submillimeter Array for the first time, that detailed the distribution of HCN, HNC, H2CO, dust inside the comae of comets C/2012 F6 and C/2012 S1.
On 2 June 2015, NASA reported that the ALICE spectrograph on the Rosetta space probe studying comet 67P/Churyumov–Gerasimenko determined that electrons produced from photoionization of water molecules by solar radiation, not photons from the Sun as thought earlier, are responsible for the degradation of water and carbon dioxide molecules released from the comet nucleus into its coma. Comas grow in size as comets approach the Sun, they can be as large as the diameter of Jupiter though the density is low. About a month after an outburst in October 2007, comet 17P/Holmes had a tenuous dust atmosphere larger than the Sun; the Great Comet of 1811 had a coma the diameter of the Sun. Though the coma can become quite large, its size can decrease about the time it crosses the orbit of Mars around 1.5 AU from the Sun. At this distance the solar wind becomes strong enough to blow the gas and dust away from the coma, enlarging the tail. Comets were found to emit X-rays in late-March 1996; this surprised researchers, because X-ray emission is associated with high-temperature bodies.
The X-rays are thought to be generated by the interaction between comets and the solar wind: when charged ions fly through a cometary atmosphere, they collide with cometary atoms and molecules, "ripping off" one or more electrons from the comet. This ripping off leads to the emission of far ultraviolet photons. With basic Earth-surface based telescope and some technique, the size of the coma can be calculated. Called the drift method, one locks the telescope in position and measures the time for the visible disc pass through the field of view; that time multiplied by the cosine of the comet's declination, times.25, should equal the coma's diameter in arcminutes. If the distance to the comet is known the apparent size of the coma can be determined. In 2015, it was noted that the ALICE instrument on the ESA Rosetta spacecraft to comet 67/P, detected hydrogen, oxygen and nitrogen in the coma, which they called the comet's atmosphere. Alice is an ultraviolet spectrograph, it found that electrons created by UV light were colliding and breaking up molecules of water and carbon monoxide.
OAO-2 discovered large halos of hydrogen gas around comets. Space probe Giotto detected hydrogen ions at distance of 7.8 million km away from Halley when it did close flyby of the comet in 1986. A hydrogen gas halo was detected to be 15 times the diameter of Sun; this triggered NASA to point the Pioneer Venus mission at the Comet, it was determined that the Comet emitting 12 tons of water per second. The hydrogen gas emission has not been detected from Earth's surface because those wavelengths are blocked by the atmosphere; the process by which water is broken down into hydrogen and oxygen was studied by the ALICE instrument aboard the Rosetta spacecraft. One of the issues is where the hydrogen is coming from and how: First, an ultraviolet photon from the Sun hits a water molecule in the comet's coma and ionises it, knocking out an energetic electron; this electron hits another water molecule in the coma, breaking it apart into two hydrogen atoms and one oxygen, energising them in the process.
These atoms emit ultraviolet light, detected at characteristic wavelengths by Alice. A hydrogen gas halo three times the size of the Sun was detected by Skylab around Comet Kohoutek in the 1970s. SOHO detected a hydrogen gas halo bigger than 1 AU in radius around Comet Hale–Bopp. Water emitted by the comet is broken up by sunlight, the hydrogen in turn emits ultra-violet light; the halos have been measured to be ten billion meters across 10 many times bigger than the Sun. The hydrogen atom are light so they can travel a long distance before they are themselves ionized by the Sun; when the hydrogen atoms are ionized they are swept away by the solar wind. The Rosetta mission found carbon monoxide, carbon dioxide, ammonia and methanol in the Coma of Comet 67P, as well as small amounts of formaldehyde, hydrogen sulfide, hydrogen cyanide, sulfur dioxide and carbon disulfide; the four top gases in 67P's halo were water, carbon dioxide, carbon monoxide, oxygen. The ration of oxygen to water coming off the comet remained constant for several months.
Coma Comet nucleus Extraterrestrial atmospheres Comet appearance and structure NASA - Comets NASA - Cosmos - Comets
The nucleus is the solid, central part of a comet, popularly termed a dirty snowball or an icy dirtball. A cometary nucleus is composed of rock and frozen gases; when heated by the Sun, the gases sublimate and produce an atmosphere surrounding the nucleus known as the coma. The force exerted on the coma by the Sun's radiation pressure and solar wind cause an enormous tail to form, which points away from the Sun. A typical comet nucleus has an albedo of 0.04. This is blacker than coal, may be caused by a covering of dust. Results from the Rosetta and Philae spacecraft show that the nucleus of 67P/Churyumov–Gerasimenko has no magnetic field, which suggests that magnetism may not have played a role in the early formation of planetesimals. Further, the ALICE spectrograph on Rosetta determined that electrons produced from photoionization of water molecules by solar radiation, not photons from the Sun as thought earlier, are responsible for the degradation of water and carbon dioxide molecules released from the comet nucleus into its coma.
On 30 July 2015, scientists reported that the Philae spacecraft, that landed on comet 67P/Churyumov-Gerasimenko in November 2014, detected at least 16 organic compounds, of which four were detected for the first time on a comet. Comets, or their precursors, formed in the outer Solar System millions of years before planet formation. How and when comets formed is debated, with distinct implications for Solar System formation and geology. Three-dimensional computer simulations indicate the major structural features observed on cometary nuclei can be explained by pairwise low velocity accretion of weak cometesimals; the favored creation mechanism is that of the nebular hypothesis, which states that comets are a remnant of the original planetesimal "building blocks" from which the planets grew. Astronomers think that comets originate in both the scattered disk. Most cometary nuclei are thought to be no more than about 16 kilometers across; the largest comets that have come inside the orbit of Saturn are C/2002 VQ94, Hale–Bopp, 29P, 109P/Swift–Tuttle, 28P/Neujmin.
The potato-shaped nucleus of Halley's comet contains equal amounts of dust. During a flyby in September 2001, the Deep Space 1 spacecraft observed the nucleus of Comet Borrelly and found it to be about half the size of the nucleus of Halley's Comet. Borrelly's nucleus was potato-shaped and had a dark black surface. Like Halley's Comet, Comet Borrelly only released gas from small areas where holes in the crust exposed the ice to sunlight; the nucleus of comet Hale–Bopp was estimated to be 60 ± 20 km in diameter. Hale-Bopp appeared bright to the unaided eye because its unusually large nucleus gave off a great deal of dust and gas; the nucleus of P/2007 R5 is only 100–200 meters in diameter. The largest centaurs are estimated to be 250 km to 300 km in diameter. Three of the largest would include 10199 Chariklo, 2060 Chiron, the lost 1995 SN55. Known comets have been estimated to have an average density of 0.6 g/cm3. Below is a list of comets that have had estimated sizes and masses. About 80% of the Halley's Comet nucleus is water ice, frozen carbon monoxide makes up another 15%.
Much of the remainder is frozen carbon dioxide and ammonia. Scientists think; the nucleus of Halley's Comet is an dark black. Scientists think that the surface of the comet, most other comets, is covered with a black crust of dust and rock that covers most of the ice; these comets release gas only when holes in this crust rotate toward the Sun, exposing the interior ice to the warming sunlight. The composition of water vapor from Churyumov–Gerasimenko comet, as determined by the Rosetta mission, is different from that found on Earth; the ratio of deuterium to hydrogen in the water from the comet was determined to be three times that found for terrestrial water. This makes it unlikely. On 67P/Churyumov–Gerasimenko comet, some of the resulting water vapour may escape from the nucleus, but 80% of it recondenses in layers beneath the surface; this observation implies that the thin ice-rich layers exposed close to the surface may be a consequence of cometary activity and evolution, that global layering does not occur early in the comet's formation history.
Measurements carried out by the Philae lander on 67P/Churyumov–Gerasimenko comet, indicate that the dust layer could be as much as 20 cm thick. Beneath, hard ice, or a mixture of ice and dust. Porosity appears to increase toward the center of the comet. While most scientists thought that all the evidence indicated that the structure of nuclei of comets is processed rubble piles of smaller ice planetesimals of a previous generation, the Rosetta mission dispelled the idea that comets are "rubble piles" of disparate material; the nucleus of some comets may be fragile, a conclusion supported by the observation of comets splitting apart. Splitting comets include 3D/Biela in 1846, Shoemaker–Levy 9 in 1992, 73P/Schwassmann–Wachmann from 1995 to 2006. Greek historian Ephorus reported that a comet split apart as far back as the winter of 372–373 BC. Comets are suspected of splitting due to internal gas pressure, or impact. Comets 42P/Neujmin and 53P/Van Biesbroeck appear to be fragments of a parent comet.
Numerical integrations have shown that both comets h
The Zimmerwald Observatory is an astronomical observatory owned and operated by the AIUB, the Astronomical Institute of the University of Bern. Built in 1956, it is located at Zimmerwald, 10 kilometers south of Bern, Switzerland. Numerous comets and asteroids have been discovered by Paul Wild at Zimmerwald Observatory, most notably comet 81P/Wild, visited by NASA's Stardust space probe in 2004; the main belt asteroid. The 1-meter aperture ZIMLAT telescope was inaugurated in 1997. List of largest optical reflecting telescopes Swiss Space Office Zimmerwald Observatory