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Sum up the information about Radar Guns.
LESSON 7. RADIO TELESCOPE
1. Read the new words:
radio telescope радиотелескоп
to emit излучать, испускать, выделять
reflector отражатель, рефлектор , зеркальный телескоп
wavelength длина волны
light wave световая волна
to focus собирать, сосредоточивать, помещать в фокусе; фокусировать
steerable paraboloid управляемая параболическая антенна
to dub копировать
pickup antenna приёмная антенна
feedпитающий механизм, (электро) снабжение, облучатель (антенны)
broad bandwidth широкий диапазон
continuum континуум, сплошная среда
radio spectrum спектр радиочастот
frequency range частотный диапазон
time-consuming отнимающий много времени, связанный с тратой времени; трудоемкий
to restrict ограничивать
frequency channel частотный канал
radiometer радиометр, радиометрический приемник; измерительный приемник
weak source источник малой интенсивности
radio emission излучение радиоволн
to amplify усиливать, увеличивать
performanceработа; функционирование, эффективность
to limit ограничивать, служить границей, пределом
to depart отклоняться, уклоняться; отступать
wind load ветровая нагрузка
2. Read the text and translate it:
Radio telescope is an astronomical instrument which is used to detect radio-frequency radiation emitted by extraterrestrial sources.
Radio telescopes are much larger than optical telescopes because radio wavelengths are much longer than optical wavelengths. The longer wavelengths means that the radio waves have lower energy than optical light waves. In order to collect enough radio photons to detect a signal, the radio dishes must be very large. Both optical and radio telescope reflectors use a parabolic shape to perfectly focus the light to a point.
The first radio telescope, built in 1937 by Grote Reber of Wheaton, Ill., U.S., was a steerable paraboloid--i.e., a device with a parabolically shaped reflector, dubbed the "dish," that focuses the incoming radio waves onto a small pickup antenna, or "feed."
Radio telescopes are used to measure broad-bandwidth continuum radiation as well as spectroscopic features due to atomic and molecular lines found in the radio spectrum of astronomical objects. In early radio telescopes, spectroscopic observations were made by tuning a receiver across a sufficiently large frequency range to cover the various frequencies of interest. This procedure, however, was extremely time-consuming and greatly restricted observations. Modern radio telescopes observe simultaneously at a large number of frequencies by dividing the signals up into as many as several thousand separate frequency channels that may range over a total bandwidth of tens to hundreds of megahertz.
Radio telescopes vary widely, but they all have two basic components: a large radio antenna and a radiometer or radio receiver. The sensitivity of a radio telescope, i.e., the ability to measure weak sources of radio emission--depends on the area and efficiency of the antenna, the sensitivity of the radio receiver used to amplify and detect the signals, and the duration of the observation.
The performance of a radio telescope is limited by various factors: the accuracy of a reflecting surface that may depart from the ideal shape because of manufacturing irregularities; the effect of wind load; thermal deformations that cause differential expansion and contraction; and deflections due to changes in gravitational forces as the antenna is pointed to different parts of the sky.
3. Answer the following questions:
1) Is the radio telescope used to detect radio-frequency radiation?
2) Are radio telescopes larger than optical telescopes?
How can you explain it?
3) When was the first radio telescope built?
4) What do you know about spectroscopic observations in early radio telescopes?
5) How do modern radio telescopes observe?
6) What are the basic components of a radio telescope?
7) What is the sensitivity of a radio telescope?
8) What factors do limit the performance of a radio telescope?
4. Correct the wrong statements:
1) Radio telescopes allow astronomers to observe radio waves which have much longer wavelengths than does visible light coming from space.
2) Radio telescopes are smaller than optical telescopes.
3) A radio telescope typically consists of a bowl-shaped antenna similar to a modern satellite dish.
4) The first radio telescope was built in 1973 by Grote Wheaton.
5) In early radio telescopes spectroscopic observations were energy – efficient and time – consuming.
6) The sensitivity of a radio telescope is the ability to restrict observations.
7) Thermal deformations cause differential expansion and make the antenna point to different parts of the sky.
5. Supply the missing connectors (not only … but also, both … and, as well as) in
the following sentences:
Astronomers gain a much more complete understanding of the universe studying in the sky with _________ radio and optical telescopes.
Radio telescopes are used to measure broad-bandwidth continuum radiation __________ spectroscopic features.
As the name suggests, radio telescopes allow astronomers to observe ___________ radio waves, but also microwaves coming from space.
Some radio telescopes are placed in protective radomes that can nearly eliminate the effect of ___________ wind loading and temperature differences throughout the structure.
There have been developed special materials that _________ exhibit very low absorption, but also reflection of radio waves.
The sensitivity of a radio telescope depends ___________ on the area and efficiency of the antenna.
Radio reflector consists a parabolic antenna which operates _____________ a television-satellite receiving antenna.
___________ optical and radio telescope reflectors use a parabolic shape to perfectly focus the light to a point.
Radio telescope antenna not only gathers the minute amount of radio frequency energy from the sky ____________ transforms it to a tiny electrical current.
Pulsars __________ quasars produce radio-frequency radiation and so are only visible in the radio region of electromagnetic spectrum.
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