printing block

Telescope is an optical instrument that uses concave lens and convex lens to observe distant objects. The light passing through the lens is refracted or reflected by concave mirror into the pinhole to converge and image, and then it is seen through the magnifying eyepiece. Also known as "a thousand-mile mirror". The first function of the telescope is to enlarge the opening angle of distant objects, so that the human eye can see the details with smaller angular distance. The second function of the telescope is to send the light beam collected by the objective lens, which is much thicker than the pupil diameter (up to 8 mm), to the human eye, so that the observer can see dim objects that he could not see before. 1608, the Dutch Hans Kenneth Lieberthal invented the first telescope. 1609 Italian Florentine Galileo Galili Lei Faming made a 40x telescope, which is the first practical telescope put into scientific application.

Coating on Telescope: Maintenance of Telescope The most famous 14 telescope in 400 years.

1, Galileo Refraction Telescope 2, Newton reflecting telescope 3, Herschel Telescope 4, yerkes Refraction Telescope 5, Mount Wilson 60-inch Telescope 6, Hook 100-inch Telescope 7, Sea Ear 200-inch Telescope 8, Horn Antenna 9, Very Large Array Radio Telescope 10, Hubble Space Telescope1. Keck series telescope 12, Si Long 2.5m telescope 13, Wilkinson Cosmic Microwave Anisotropy Exploration Satellite 14 and Swift Observation Satellite.

Hubble Space Telescope Compton Gamma-ray Space Telescope Chandra X-ray Space Telescope XMM- Newton X-ray Space Telescope wilkinson microwave anisotropy probe Spitzer Space Telescope Fermi Gamma-ray Space Telescope James Webb Space Telescope started editing this telescope (telescope/binoculars).

/kloc-One day at the beginning of the 7th century, Hans Lippershey, the owner of an optical shop in a small Dutch town, arranged a convex lens and a concave lens in a line to check the quality of the polished lens. Looking through the lens, he found that the church spire in the distance seemed to be getting closer and closer, so he accidentally discovered the secret of the telescope. 1608, he applied for a patent for his telescope, and made a binoculars according to the requirements of the authorities. It is said that dozens of opticians in the town claimed to have invented the telescope.

Edit this paragraph definition

The basic principle of telescope is a visual optical instrument used to observe distant objects. It can enlarge the small opening angle of distant objects according to a certain proportion, so that they have a larger opening angle in the image space, and make the objects that were invisible or unclear to the naked eye become clear. Therefore, the telescope is an indispensable tool in astronomy and ground observation. It is an optical system that makes the incident parallel beams pass through the objective lens and eyepiece and still exit in parallel. According to the principle of telescope, it is generally divided into three types. Bosma tube wave telescope

An instrument for observing distant objects by collecting electromagnetic waves. In daily life, telescopes mainly refer to optical telescopes. But in modern astronomy, astronomical telescopes include radio telescopes, infrared telescopes, X-ray telescopes and gamma-ray telescopes. In recent years, the concept of astronomical telescope has been further extended to gravitational waves, cosmic rays, dark matter and other fields. Or through a magnifying eyepiece. Optical telescopes in daily life are also called "thousand-mile mirrors". It mainly includes amateur astronomical telescopes, theater telescopes and military binoculars.

Edit the introduction of this paragraph.

The commonly used binoculars need to add a prism system in order to reduce the volume and flip the inverted image. According to different forms, prism system can be divided into RoofPrism system (Schmidt roof prism system) and PorroPrism system (ontological system). The principles and applications of these two systems are similar. Small hand-held telescope for personal use should not use too large magnification, which is generally 3 ~ 12 times. If the magnification is too large, the image definition becomes worse and the jitter is serious. Telescopes larger than 12 times are generally fixed by tripod or other means.

Edit this paragraph history

At the same time, the German astronomer Kepler began to study telescopes. He proposed another kind of astronomical telescope in Bending Optics, which consists of two convex lenses. Unlike Galileo's telescope, it has a wider field of vision than galileo telescope. But Kepler didn't make the telescope he introduced. Sagana first made this telescope between1613-1617. He also made a telescope with a third convex lens according to Kepler's suggestion, and turned the inverted image of the telescope composed of two convex lenses into a positive image. Sagana made eight telescopes, one for observing the sun, and no matter which one can see sunspots with the same shape. Therefore, he dispelled many people's illusion that sunspots may be caused by dust on the lens, and proved that sunspots are really observed. When observing the sun, Sagina installed special shading glass, but Galileo did not add this protective device. As a result, he hurt his eyes and finally became almost blind. Huygens of the Netherlands made a telescope with a tube length of nearly 6 meters to explore Saturn's rings in 1665, and later made a telescope with a tube length of nearly 4 1 meter. A telescope that uses a lens-cutting mirror is called a refractive telescope. Even if the lens barrel is lengthened and the lens is machined accurately, the chromatic aberration cannot be eliminated. Newton once thought that the chromatic aberration of refractive telescope was hopeless, but it turned out to be too pessimistic. 1668, he invented the reflective telescope, which solved the problem of chromatic aberration. The first reflective telescope was very small. The aperture of the mirror in the telescope was only 2.5 cm, but the profit and loss of Jupiter's satellite and Venus could be clearly seen. 1672, Newton made a larger reflecting telescope and gave it to the Royal Society, which is still kept in the library of the Royal Society. 1733, an Englishman Hal made the first achromatic refraction telescope. 1758, the same telescope was made in Boland, London. He made convex lenses and concave lenses from glasses with different refractive indexes to offset the colored edges they formed. However, it is not easy to make a big shot. At present, the largest refracting telescope in the world has a diameter of 102 cm and is installed at the Addis Observatory. Monocular

1793, William Herschel of England made a reflective telescope. The reflector has a diameter of 1 30cm, is made of copper-tin alloy and weighs1ton. The reflecting telescope made in william parsons, England in 1845, the diameter of the reflector is1.82m .. 19 17, and the Hooke telescope was built at Mount Wilson Observatory in California, USA. Its primary mirror aperture is 100 inch. It was with this telescope that Edwin Hubble discovered the amazing fact that the universe is expanding. 1930, BernhardSchmidt, Germany, combines the advantages of refractive telescope and reflecting telescope (refractive telescope has small aberration but chromatic aberration, and the larger the size, the more expensive it is; Reflective telescope has no chromatic aberration, and its cost is low. The reflector can be made large, but there is chromatic aberration), and the first folding reflective telescope is made. After the war, reflective telescopes developed rapidly in astronomical observation. 1950, Haier reflective telescope with a diameter of 5.08m was installed on the Paloma Mountain. 1969, a reflector with a diameter of 6 meters was installed on Pastuhov Mountain in the North Caucasus of the former Soviet Union. 1990, NASA put the Hubble Space Telescope into orbit. However, due to the mirror failure, the Hubble Space Telescope didn't play its full role until 1993 astronauts completed the space repair and replaced the lens. Because it can not be disturbed by the earth's atmosphere, the image clarity of Hubble telescope is 10 times that of similar telescopes on earth. 1993, the Keck telescope with a diameter of 10 meter was built in Monaque Mountain, Hawaii, and its mirrors were composed of 36 mirrors with a diameter of 1.8 meter. 200 1 the European southern observatory in Chile has developed the "VLT", which consists of four 8-meter-diameter telescopes, and its light-gathering capacity is equivalent to one 16-meter reflective telescope. Now, a number of telescopes under construction have begun to attack the White Giant brothers on Mount Monaque. These new competitors include the California Giant Telescope (CELT) with a diameter of 30m, the Giant Magellanic Telescope (GMT) with a diameter of 20m and the Overwhelming Telescope (OWL) with a diameter of 100m. Their supporters point out that these new telescopes can not only provide space pictures with far better image quality than Hubble, but also collect more light, learn more about the initial stars and cosmic gases when galaxies formed 654.38 billion years ago, and clearly see the planets around distant stars.

Edit this section of the Hubble Space Telescope.

Hubble Space Telescope

(Hubble Space Telescope, HST), the first human space telescope, has a total length of over13m and a mass of over1/ton. It runs in an orbit about 600 kilometers above the ground at the outer edge of the earth's atmosphere. It goes around the earth about every 100 minute. Hubble telescope was launched into orbit by NASA and European Space Agency in 1990. Hubble telescope is named after astronomer Edwin Hubble. According to the plan, it will be replaced by James Webb Space Telescope in 20 13. The angular resolution of Hubble telescope is less than 0. 1 sec, and it can acquire 3 to 5 gigabytes of data every day. Because of its operation in outer space, the images obtained by Hubble telescope are not affected by atmospheric disturbance and refraction, and infrared spectral images that are usually absorbed by the atmosphere can be obtained. The Hubble data are analyzed and processed by astronomers and scientists from the Space Telescope Institute. The Institute is affiliated to Johns Hopkins University in Baltimore, Maryland, USA.

history

The idea of Hubble Space Telescope can be traced back to 1946. This telescope was designed, built and launched in A.D. 1970, and cost 2 billion dollars. NASA Marshall Space Flight Center is responsible for the design, development and construction of Hubble Space Telescope. NASA Goddard Space Flight Center is responsible for scientific equipment and ground control. Perkin Elmer is in charge of making the lens. Lockheed is responsible for building telescope mirrors.

Ascend to the sky

The telescope was launched with the space shuttle Discovery on April 24th, 1990. It was originally scheduled to be launched in 1986, but the launch date was postponed after the explosion of Challenger in 1 month that year. The first images sent back to Earth disappointed astronomers and many others. Because Perkin Elmer made the wrong lens thickness, it caused serious spherical aberration and the image was hazy.

Maintenance task (1)

The clear image taken after changing the equipment is much clearer than before. The first task was called STS-6 1,199365438+In February, many new instruments were added, including replacing high-speed photometer (HSP) with COSTAR. Replace WFPC camera with WFPC2 camera. Replace the solar collector. Replace two RSUs, including four gyroscopes. The orbital transfer mission was announced on 1994 65438+ 10/3, and the first clear images were taken and sent back to Earth.

Maintenance tasks (2)

The second task, STS-8 1, started in February 1997. Two instruments and multiple hardware of the telescope were replaced.

Maintenance task (3)A

Task 3A is called STS- 103, and started in February 1999.

Maintenance task (3)B

Task 3B named STS- 109 started in March 2002.

Edit this paragraph classification

First, the refracting telescope

Refraction telescope is a kind of telescope with lens cutting mirror. There are two kinds: galileo telescope with concave lens as eyepiece; Kepler telescope with convex lens as eyepiece. Because the chromatic aberration and spherical aberration of Dan Toujing objective lens are quite serious, modern refractive telescopes generally use two or more lens groups. Among them, the double-lens objective lens is the most widely used. It consists of a convex lens made of crown glass and a concave lens made of flint glass. The two lenses are very close together. It can completely eliminate the position chromatic aberration of two specific wavelengths, and correspondingly weaken the position chromatic aberration of other wavelengths. When certain design conditions are met, spherical aberration and coma can be eliminated. Due to the influence of aberration such as residual chromatic aberration, the relative aperture of the dual-lens objective is relatively small, generally115-1/20, and rarely larger than 1/7, so the available field of view is not large. A double-lens objective with a diameter less than 8 cm can glue two lenses together, which is called a double-glued objective, and a double-separated objective with a certain gap is called a double-glued objective. In order to increase the relative aperture and field of view, a multi-lens objective group can be used. For galileo telescope, the structure is very simple and the light energy loss is less. The lens barrel is short and light. And it is still a positive image, but the magnification is small and the field of vision is narrow. It is generally used for theater mirrors and toy telescopes. For Kepler telescope, it is necessary to add a prism group or lens group behind the objective lens to rotate the image, so that the eyes can observe the positive image. Refractive telescopes generally adopt Kepler structure. Because the imaging quality of refractive telescope is better than that of reflective telescope, it has a large field of view and is convenient to use and maintain. Most small and medium-sized astronomical telescopes and many special instruments use refractive systems, but the manufacture of large refractive telescopes is much more difficult than that in reflecting telescope. Because it is very difficult to smelt high-quality large-aperture lenses, and there is a problem of light absorption by glass, large-aperture telescopes are all reflective (described in detail below).

galileo telescope

The objective lens is a convergent lens and the eyepiece is a telescope with a divergent lens. The real image formed by the refraction of light through the objective lens is in the focus behind the eyepiece (near the back of the human objective lens). This image is a virtual image to the eyepiece, so it is refracted by the eyepiece to form an enlarged upright virtual image. The magnification of galileo telescope is equal to the ratio of the focal length of the objective lens to the focal length of the eyepiece. Its advantage is that the lens barrel is short and can stand upright, but the field of vision is relatively small. A device that juxtaposes two galileo telescope with low magnification and uses a bolt button in the middle to adjust its definition is called a "drama viewing mirror"; Because it is easy to carry, it is often used to watch performances. The telescope invented by Galileo plays an important role in the history of human understanding of nature. It consists of a concave lens (eyepiece) and a convex lens (objective lens). Its advantage is simple structure, which can directly form an upright image.

Kepler telescope

This principle consists of two convex lenses. Because there is a real image between the two, the reticle is easy to install and has excellent performance, so at present, military telescopes, small astronomical telescopes and other professional telescopes all adopt this structure. But the imaging of this structure is inverted, so an upright system should be added in the middle. There are two types of imaging systems: prism imaging system and lens imaging system. Our common typical binoculars with wide front and narrow back adopt a double right-angle prism imaging system. The advantage of this system is that the optical axis is folded twice at the same time, which greatly reduces the volume and weight of the telescope. It is expensive to use a complex set of lenses to invert the image. The Russian 20×50 three-section telescope not only adopts a well-designed lens upright system.

history

16 1 1 year, German astronomer Kepler used two biconvex lenses as the objective lens and eyepiece respectively, which significantly improved the magnification. Later, people called this optical system Kepler telescope. Now people are still using these two kinds of refractive telescopes, and the astronomical telescope adopts Kepler type. It should be pointed out that at that time, because the telescope used a single lens as the objective lens, there was serious chromatic aberration. In order to obtain good observation effect, a lens with small curvature is needed, which will inevitably lead to the lengthening of the mirror body. So for a long time, astronomers have been dreaming of making longer telescopes, and many attempts have ended in failure. 1757, Dulong established the theoretical basis of achromatic lenses by studying the refraction and dispersion of glass and water, and made achromatic lenses with crown glass and flint glass. Since then, the achromatic refraction telescope has completely replaced the long mirror telescope. However, due to technical limitations, it is difficult to cast large flint glass. At the beginning of achromatic telescope, only 10 cm lens can be ground at most. At the end of 19 century, with the improvement of manufacturing technology, it became possible to manufacture large-aperture refractive telescopes, and the climax of manufacturing large-aperture refractive telescopes appeared. Of the eight existing refracting telescopes over 70 cm in the world, seven were built between 1885 and 1897, among which the most representative ones are the Yekeshi telescope with the aperture of 102 cm built in 1897 and the 9/kloc telescope built in 1886. Refractive telescope has the advantages of long focal length, large negative scale and insensitivity to lens barrel bending, and is most suitable for astrometry. But there will always be residual color difference, and at the same time, it absorbs radiation in ultraviolet and infrared bands very strongly. The casting of huge optical glass is also very difficult. When the Yekeshi telescope was built in 1897, the development of refractive telescope reached its peak, and no larger refractive telescope appeared in the next hundred years. This is mainly because it is technically impossible to cast a large piece of perfect glass as a lens, and the large-size lens will be deformed obviously due to the action of gravity, thus losing Ming Rui's focus.

Second, reflecting telescope.

This is a telescope with a concave mirror and a cutting mirror. Can be divided into Newton telescope, seglin telescope and other types. The main advantage of reflective telescope is that there is no chromatic aberration. When the objective lens is a paraboloid, spherical aberration can be eliminated. However, in order to reduce the influence of other aberrations, the available field of view is smaller. The material for making the mirror surface only requires small expansion coefficient, small stress and easy grinding. Generally, polishing mirrors are coated with aluminum film, and the reflectivity of aluminum film is more than 80% in the range of 2000-9000 angstroms, so reflective telescopes are suitable for studying near infrared and near ultraviolet bands in addition to optical bands. The relative aperture of reflecting telescope can be made larger. The relative aperture of the main focal reflecting telescope is about 1/5- 1/2.5, or even larger. Except for Newton telescope, the length of the lens barrel is much shorter than the focal length of the system. In addition, only one surface of the primary mirror needs to be machined, which greatly reduces the cost and manufacturing difficulty. So now the aperture is greater than 1.34 meters. For the reflective telescope with larger aperture, prime focusing system (or Newton system), Casselin system and folding axis system can be obtained by replacing different secondary mirrors. In this way, the telescope can obtain several different relative apertures and fields of view. Reflecting telescope is mainly used in astrophysics.

history

The first reflecting telescope was born in 1668. Newton decided to use a spherical mirror as the main mirror after many failures in grinding aspheric lenses. He grinds out a concave mirror with a diameter of 2.5cm, and places a reflector with an angle of 45o in front of the focus of the main mirror, so that the concentrated light reflected by the main mirror can be reflected from the lens barrel to the eyepiece at an angle of 90o. This system is called Newton reflecting telescope. Although its spherical mirror will produce some aberrations, it is very successful to replace the refracting mirror with the reflecting mirror. In 1663, James Gregory proposed a scheme: use a primary mirror and a secondary mirror, both of which are concave mirror. The secondary mirror is placed outside the focus of the primary mirror, and a small hole is left in the center of the primary mirror, so that the light is reflected twice by the primary mirror and the secondary mirror and then exits from the small hole and reaches the eyepiece. The purpose of this design is to eliminate spherical aberration and chromatic aberration at the same time, which requires a parabolic primary mirror and an ellipsoidal secondary mirror, which is correct in theory, but the manufacturing level at that time could not meet this requirement, so Gregory could not get a useful mirror for him. 1672, Frenchman seglin put forward the third design scheme of reflective telescope. The structure is similar to Gregory telescope, except that the secondary mirror is convex in front of the focus of the primary mirror, which is the most commonly used Cassegrain reflective telescope. This makes the light reflected by the secondary mirror slightly divergent, reducing the magnification, but eliminating the spherical aberration, so that the telescope can also make the focal length very short. The primary mirror and secondary mirror of seglin telescope can have many different forms, and their optical properties are also different. Because of the long focal length, short mirror body and large magnification of seglin telescope, the images obtained are clear; Seglin focus can be used to study celestial bodies with small field of view, while Newton focus can be configured to shoot large-area celestial bodies. Therefore, seglin telescope has been widely used. Herschel is a master of making reflecting telescope. He was a musician in his early years. Because he loves astronomy, he began to grind telescopes from 1773 and made hundreds of telescopes in his life. In the telescope made by Herschel, the objective lens is obliquely placed in the lens barrel, so that the parallel light is reflected and converged on one side of the lens barrel. In the nearly 200 years after the invention of reflective telescope, reflective materials have been an obstacle to its development: bronze casting mirrors is easy to corrode and must be polished regularly, which requires a lot of money and time, while metals with good corrosion resistance are denser and more expensive than bronze. 1856, justus von liebig, a German chemist, invented a method that can coat a thin layer of silver on glass and reflect light efficiently after polishing. In this way, it is possible to make a better and larger reflective telescope. 19 18 At the end of this year, the Hooke telescope with a diameter of 254 cm was put into use and was built by Haier. Astronomers used this telescope to reveal for the first time the true size of the Milky Way and our position in it. More importantly, Hubble's theory of cosmic expansion is the result of observation with Hooke telescope. In the 1920s and 1930s, the success of Hooke Telescope inspired astronomers to build a bigger reflecting telescope. 1948, the United States built a telescope with a diameter of 508 cm. In order to commemorate Haier, an outstanding telescope manufacturer, it was named Haier Telescope. Haier telescope has been designed and manufactured for more than 20 years. Although it has a farther field of vision and stronger resolution than Hooke telescope, it has not given mankind an updated understanding of the universe. As Asimov said, "The Haier telescope (1948), like the Yekeshi telescope (1897) half a century ago, seems to indicate that a certain type of telescope has almost come to an end". 1976, the former Soviet Union built a 600 cm telescope, but its function is not as good as Haier telescope, which also confirms what Asimov said. Reflective telescope has many advantages, for example, it has no chromatic aberration, can record the information sent by celestial bodies in a wide range of visible light, and is easier to make than refractive telescope. However, due to its inherent shortcomings, such as the larger the aperture, the smaller the field of view, and the need for periodic coating of the objective lens.

Third, the folding reflecting telescope.

On the basis of spherical reflector, a refractive element for correcting aberration is added, which can avoid difficult large aspheric surface processing and obtain good image quality. There is a famous Schmidt telescope, and a Schmidt correction plate is placed in the center of the spherical mirror. It is an aspheric surface with one side flat and the other side slightly deformed, which makes the central part of the beam slightly converge and the peripheral part slightly diverge, just to correct spherical aberration and coma. Another kind of Maksutov telescope can correct spherical aberration and coma at the same time by adding a meniscus lens in front of the spherical mirror and choosing appropriate parameters and positions of the meniscus lens. And the derivatives of these two kinds of telescopes, such as super Schmidt telescope, Baker-Noon camera and so on. In catadioptric reflecting telescope, the image is imaged by a mirror, and the refractive mirror is used to correct the aberration. Its characteristics are relatively large aperture (even greater than 1), strong light, wide field of vision and excellent imaging quality. Suitable for sky survey photography and observation of nebulae, comets, meteors and other celestial bodies. If catadioptric card seglin system is used in small vision telescope, the lens barrel can be very short.

history

Reflecting telescope first appeared in 18 14. 193 1 year, the German optician Schmidt used a unique aspheric thin lens close to a parallel plate as a correcting mirror, and cooperated with a spherical reflector to make a Schmidt-type folded reflecting telescope that can eliminate spherical aberration and off-axis aberration. This kind of telescope has strong optical power, large field of view and small aberration, and is suitable for shooting large-area photos of the sky, especially for shooting dim nebulae. Schmidt telescope has become an important tool for astronomical observation. 1940, Maksutov made another kind of folded reflecting telescope with meniscus lens as corrective lens. Its two surfaces are two spherical surfaces with different curvatures, with little difference, but with great curvature and thickness. All its surfaces are spherical, which makes it easier to grind than the correction plate of Schmidt telescope, and the lens barrel is shorter, but the field of view is smaller than that of Schmidt telescope, which requires higher glass. Because folding reflecting telescope can take into account the advantages of both refractive and reflective telescopes, it is very suitable for amateur astronomical observation and astrophotography, and is loved by the vast number of astronomical enthusiasts.

radio telescope

Basic equipment for detecting radio emission of celestial bodies. It can measure the intensity, spectrum and polarization equivalence of celestial radio. It usually consists of antenna, receiver and terminal equipment. The antenna collects the radio emission of celestial bodies, and the receiver processes these signals and converts them into a form that can be recorded and displayed. The terminal equipment records the signal, performs some processing according to the specific requirements, and then displays it. Spatial resolution and sensitivity are the basic indexes to characterize the performance of radio telescopes. The former reflects the ability to distinguish radio point sources close to each other on two celestial spheres, while the latter reflects the ability to detect weak radio sources. Radio telescopes usually require high spatial resolution and high sensitivity. According to different antenna structures, radio telescopes can be divided into two categories: continuous aperture and discontinuous aperture. The former is a classical single dish parabolic antenna radio telescope, and the latter is a variety of combined antenna systems based on interference technology. In 1960s, two new types of discontinuous aperture radio telescopes, very long baseline interferometer and synthetic aperture radio telescope, appeared. The former has extremely high spatial resolution, while the latter can obtain clear radio images. The world's largest traceable classical radio telescope has a parabolic antenna with a diameter of 100 m, which is installed at the Max Planck Institute for Radio Astronomy in Germany. The largest discontinuous aperture radio telescope in the world is a very large antenna array, which is installed in the National Radio Observatory. 193 1 year, in Bell Laboratories, New Jersey, USA, KG Jansky, an American in charge of searching and identifying telephone interference signals, found that there was a maximum radio interference every 23 hours, 56 minutes and 04 seconds. After careful analysis, he asserted in an article published in 1932 that this was a radio emission from the Milky Way. Therefore, Jansky initiated a new era of studying celestial bodies with radio waves. At that time, he used a rotating antenna array with a length of 30.5 meters and a height of 3.66 meters to obtain a "fan-shaped" directional beam with a width of 30 degrees at the wavelength 14.6 meters. Since then, the history of radio telescopes has been a history of constantly improving resolution and sensitivity. Ever since Jansky announced that he had received the radio signal from the Milky Way, American G Rabe devoted himself to the trial production of the radio telescope, which was finally made in 1937. This is a unique parabolic radio telescope in the world before World War II. Its parabolic antenna has a diameter of 9.45 meters, and a pencil beam of 12 degrees is obtained at the wavelength of 1.87 meters to measure the radio waves emitted by celestial bodies such as the sun. Therefore, Raber is called the pioneer of parabolic radio telescope. Radio telescope is the basic equipment for observing and studying celestial radio waves, which includes directional antenna for collecting radio waves, high-sensitivity receiver for amplifying radio signals, information recording, processing and display system, etc. According to the basic principle of radio telescope and optical reflecting telescope, the projected electromagnetic waves will reach the common focus in the same phase after being reflected by an accurate mirror. Using a paraboloid of revolution as a reflector, it is easy to realize in-phase light gathering. Therefore, the antennas of radio telescopes are mostly parabolic. Radio observation is carried out in a wide frequency range, and the radio technology of detection and information processing is more flexible and diverse than that of optical Bosch, so there are more types of radio telescopes and various classification methods. For example, according to the shape of the receiving antenna, it can be divided into parabolic, parabolic cylindrical, spherical, parabolic cut-band, pull, spiral, traveling wave, antenna and other radio telescopes; According to the shape of directional beam, it can be divided into pencil beam, fan beam and multi-beam radio telescope. According to the observation purpose, it can be divided into radio telescopes such as mapping, positioning, calibration, polarization, spectrum and solar image. According to the type of work, it can be divided into full power, swept frequency, fast imaging and other types of radio telescopes.

space telescope

A large telescope for astronomical observation outside the earth's atmosphere. Because it avoids the influence of the atmosphere and will not be distorted by gravity, it can greatly improve the observation ability and resolution, and even make some optical telescopes observe near infrared and near ultraviolet at the same time. However, there are many new strict requirements in manufacturing, for example, the mirror machining accuracy should be within 0.0 1 micron, and all components and mechanical structures should be able to withstand the vibration and overweight during launch, but they should be as light as possible to reduce the launch cost. The first space telescope, also known as Hubble telescope, was put into orbit 600 kilometers above the ground by the American space shuttle Discovery on April 24th, 1990. Its overall shape is cylindrical, with a length of 13m and a diameter of 4m. The front end is a telescope, and the back half is an auxiliary instrument, with a total weight of about11t. The telescope has an effective aperture of 2.4 meters and a focal length of 57.6 meters. The observation wavelength ranges from ultraviolet 120 nm to infrared 1200 nm, and the cost is1500 million USD. The resolution of the original design is 0.005, which is 100 times that of the ground telescope. However, due to a small negligence in manufacturing, it was not until the last day that there was a big spherical error in the instrument, which seriously affected the observation quality. 19931February 2 ~ 13, the American space shuttle Endeavour carried seven astronauts, successfully replaced 1 1 components for Hubble, completed the repair work, and created the history of human repairing large spacecraft in space. The successfully repaired Hubble telescope will continue to provide information on the depth of the universe for 10 years. 199 1 In April, the United States launched the second space telescope, which is a device for observing gamma rays. Total weight 17 ton, power consumption 1.52 watt, signal transmission rate 17000 bit/s, carrying four groups of detectors, with angular resolution of 5'~ 65438. Its service life is about 2 years.

/view/25265.htm#sub25265