Most often, when it comes to the “best” category, it belongs to either the Arabs or the Chinese, and quite often they take the palm from each other. Whatever is created in the world, one of these guys will always make it bigger, more expensive, taller, more futuristic and generally larger-scale. Not long ago, the Chinese managed to become one of the top three owners of the world's largest radio telescopes, where the FAST telescope with its size took second place.
In the list of the largest radio telescopes, the FAST telescope is inferior in size to the Russian RATAN-600, which is in Karachay-Cherkessia, not far from the village of Zelenchukskaya, at an altitude of 970 meters, with a collective area of 12 thousand m² and a diameter of 576 meters. However, the RATAN-600 antenna type has a ring-shaped shape, and the FAST telescope has a fixed spherical shape, and by this type it is the largest in the world, with the largest collecting area, overtaking the American Arecibo, in Puerto Rico.
The FAST telescope stands for “Five hundred meter Aperture Spherical Telescope”, which means “Radio telescope with a five hundred meter aperture”; the Chinese call this technique Tianyang, which means “Eye of Heaven”. The radio telescope was built in Guizhou Province, southwest China. To reduce the cost of construction, the FAST telescope was made in the “Earth Bowls” classification, that is, the natural terrain of the area was used as the basis of the reflector.
The Daodang karst basin in the Qiannan Bui Miao Autonomous Region, with a diameter of 800 meters, was most suitable for the construction of a radio telescope mirror. A rim was made above the surface of the basin on which a network of steel cables was placed, covered with perforated triangular aluminum panels, the number of which was 4450 units. Thus, the FAST telescope received a total physical diameter of 500 meters, of which the effective diameter is 300 meters. The collecting area of the radio telescope was about 190 thousand m².
To focus radio waves, the FAST telescope was equipped with a receiver suspended above a mirror with a focal length of 140 meters. To understand the scale, a 45-story building can be placed in the space from the reflector to the receiver! The receiver cabin is able to move through cables and servomechanisms, which are secondarily adjusted by robots for more accurate reception. The entire system of cables and servomechanisms is attached to six high support towers. The FAST telescope also has a system that allows focusing at any point in space within a deviation of ± 40 ° from the zenith.
As for the history of the project, the idea to build the FAST telescope was first put forward in 1994, but it was approved only in July 2007 by the National Development and Reform Commission. First, villages and residents living within a 5-kilometer radius of the project were resettled. At the end of 2008, the first foundation laying took place. Construction of the structure itself began in March 2011, lasting 5 years until July 2016. The FAST telescope cost China $180 million.
— The whole world was talking about the largest radio telescope, which was launched yesterday in China. How do you assess the importance of this event?
“It would probably be more correct to call this the official completion of the telescope’s construction.” You can call this a discovery, but you need to understand that for all instruments of this class in the world, without exception, it takes years to put them into full operation.
Years since the completion of their construction is announced.
This is due to the fact that such telescopes are technologically extremely complex. And to achieve the parameters that were included in the project, a lot of work is required.
— What is special about the telescope design?
— The FAST telescope is a 500-meter mirror placed inside a natural depression, which has been slightly straightened. Its geometric shape is a sphere. It can be aimed at different objects in the sky with great difficulty, simply because different objects are in different places in the sky at different times. The telescope is similar to the 300-meter Arecibo radio telescope, which is also located in a natural depression. Sometimes, by the way, they say that Arecibo was built in the mouth of a volcano, in fact, in a karst sinkhole. Arecibo is aimed at objects in a fairly limited range of angles by moving the secondary mirror on three cables.
Our Chinese colleagues have made fundamental changes to this scheme, thanks to which FAST will have significantly greater capabilities for pointing at and tracking a celestial object.
In fact, FAST will see a much larger area of the sky, roughly about 2/3 of the entire sky.
How? FAST will actually have an active surface. The 4.5 thousand panels from which it is made cannot yet move. Therefore, the first observations will be made while the telescope is a sphere, at or near the zenith. But within a year or two, Chinese colleagues should learn to make this area active. That is, each panel in real time will be able to adapt to a paraboloid of rotation directed to the point in the sky from which we want to catch radiation. As a result, it won't lose its effective area like Arecibo does, and it will be able to target a wider range of sources and track them for longer. This is a major leap forward relative to Arecibo, not only due to an increase in area, but also due to the introduction of an active surface.
— What will this telescope be the best at?
- He will be the most sensitive. Bye. Because if you sum up the collecting surface, it has the largest one. It will only be most sensitive at the wavelengths at which it operates. Obviously, at short wavelengths it will no longer be able to compete with telescopes such as the Effelsberg antenna, Green Bank Telescope, ALMA and others.
— What are the stated and real goals of the radio telescope?
— Firstly, these are radio pulsars. Because pulsars have an incident spectrum: the shorter the wavelength, the weaker the signal. Therefore, any telescope that operates at long wavelengths is very suitable for pulsars, FAST for studying pulsars will be awesome.
Pulsars are interesting in themselves, let's not forget that they are the most accurate clocks in the world, and that today they are the coolest way to test predictions arising from the general theory of relativity.
In addition, based on pulsars, it is proposed to build a circuit that catches gravitational waves. And this scheme will not replace the ground-based gravitational interferometer LIGO simply because they are focused on studying gravitational waves of different frequencies. The many pulsars in the sky can actually be used as reference points, and we can study how the Earth shakes relative to them. After all, the Earth is the very brick that trembles when space-time changes.
The second task will be the study of dark matter.
One of the reasons we know it exists is because of the rotation curves of neutral hydrogen in the disks of galaxies. If we want to get statistics, rich material on a large number of galaxies, obviously we need a sensitive telescope, and FAST will do this.
Since this is the most sensitive telescope in the world at a wavelength of 18 cm, it will be able to do this for more galaxies located further away.
Undoubtedly, an important task will be the study of so-called ultrafast radio bursts (FRBs). Many of them are quite weak, some were just opened with the help of Arecibo. The problem with such telescopes is that the area of the sky that they can observe at any given time is small. But this problem can be solved. It is necessary to build a multi-beam system with several radiation receivers, which is somewhat reminiscent of CCD matrices in optics. If the Chinese do this, they can get serious about FRBs. And this is cool, since fast radio bursts are detected strictly at those waves on which FAST will operate.
It is still not clear what they are, there is a whole zoo of fast radio bursts, and this telescope will be able to study them much better and collect their statistics.
— The main thing is not to open microwave ovens that are not turned off. FRBs in Australia were erroneously recorded when employees near a radio telescope opened the oven door without turning it off. They didn't wait for the furnace to finish working.
— The whole world is shouting that the telescope will look for life in the Universe. Even The New York Times came out with the headline "China seeks scientific glory and aliens." Is this some kind of populism aimed at attracting attention?
— Obviously, this is being written because it is incomparably easier to explain than the scientific tasks facing the telescope. It’s just that journalists don’t bother to spend time and effort explaining it.
And they can be understood: they need to be read, and most people in the world will not spend more than a minute reading this news.
And with so many characters you won’t be able to write about anything other than “little green men”. At the same time, there is nothing shameful in searching for extraterrestrial intelligence; this is a normal task, one of many that the telescope will solve. I was in China when the FAST builders gave a report on the scientific problems that would be solved. The discussion was professional, there was no populism. This is a very serious project, and the main thing in it is not even science, but technologies that no one else has come up with before.
As for access to the telescope, obviously it will not be closed to the whole world. A couple of years ago, international working groups were organized around it to study prospects for various scientific tasks. It will be accessible to scientists around the world, just like any other major radio telescope today.
— In light of this, will the telescope be involved in such international projects as “Very Long Baseline Radio Interferometry” (VLBI), your “Radioastron” and others?
- Without a doubt, it will be. We really hope that it will be used in the Radioastron program. I hope that our Chinese colleagues will introduce interferometric mode, that is, the opportunity to participate in VLBI programs, before Radioastron ceases its activities. Today, the situation at Radioastron is very good; Roscosmos has extended funding for observations until the end of 2018.
If FAST introduces interferometry before this time, we will definitely work together.
Today, in this mod, we work with all Chinese radio telescopes. This is a 25-meter mirror in Urumqi, a 25-meter mirror near Shanghai and a 65-meter mirror also near Shanghai.
— What place does China occupy today in world radio astronomy and what will it occupy with the introduction of the new telescope?
— Our Chinese radio astronomer colleagues still have room to grow. This is clearly visible, and our Chinese colleagues themselves admit that they still have a shortage of highly qualified personnel in radio astronomy. And in this sense, FAST is one of the ways in which they can fill this shortage of personnel by conducting active training on two, and soon on three, new radio telescopes.
The first is a 65-meter full-revolving mirror with an active surface near Shanghai, which was commissioned a year ago, the second is FAST, and there will be a third
— China begins construction of a record-breaking 110-meter fully rotating telescope in Urumqi.
They will have three high-end telescopes on which they can forge their frames. Those things that their industry can produce on their own, they do themselves. And what they cannot do, they buy. For example, they buy receivers for radio telescopes and the electronics behind them in the USA from the National Radio Astronomy Observatory.
As for the future of global radio astronomy, it is moving towards a 1 square meter antenna array. km SKA (Square Kilometer Array). The first phase of SKA will be built in Australia and South Africa and will be comparable to FAST. But the second phase of SKA, which will be based on a large number of small telescopes, will be incomparably more sensitive than FAST.
— With the introduction of these capacities, will radio astronomy receive a quantitative or qualitative leap?
- Undoubtedly, high quality. Because if you are interested not only in new technologies, but also in the opportunity to make sure that a new telescope will give qualitatively new scientific results, there is an unwritten rule:
that to do this you need to build a telescope that is an order of magnitude better in one of the key parameters.
One of these parameters is sensitivity, or collecting surface. Radioastron took the path of improving angular resolution, increasing it ten times or more, and we got results that no one could have predicted before us. It’s the same with FAST - the huge collecting area will translate into quality and give interesting results.
The FAST radio telescope is a spherical radio telescope with a five hundred meter aperture, which is the literal translation from the English phrase: “Five hundred meter Aperture Spherical Telescope”, abbreviated “FAST”. The unofficial Chinese name for the telescope located in Guizhou Province is Heaven's Eye (天眼). In addition to promising scientific research, this scientific project should demonstrate China's ambitions in space exploration.
Construction of this telescope was completed in July 2016, and required five years and 180 million dollars. Since the completion of construction, the FAST Observatory has received the honorary title of radio telescope with a filled aperture of the largest diameter, namely 500 meters. Thus, FAST surpassed another giant radio telescope, which remained the largest for 53 years, with an aperture diameter of 304.8 meters.
Speaking about the largest radio telescopes with an unfilled aperture, this niche is still occupied by the Russian RATAN-600 (576 m).
Design
The design of the FAST telescope is in many ways similar to the Arecibo Observatory. Its aperture consists of 4,450 perforated triangular aluminum plates with a side of 11 meters. These plates are arranged in a geodesic dome on suspended steel cables forming a grid. The entire aperture is located in a natural depression - a karst funnel. It is noteworthy that the depression itself is formed in the mountains, at an altitude of about 1 km above sea level, which also has a positive effect on the quality of observations carried out by FAST in the future.
Unlike Arecibo Observatory's static aperture, each panel of the FAST radio telescope is capable of changing its position using hydraulic actuators that move a grid of tethers.
Above the dish-shaped reflector there is a movable cabin, which is moved by cable robots. The receiving antennas located in the center of the “dish” are also movable, as they are installed on a movable platform (Hugh-Stewart).
Characteristics
According to information received from Chinese media, the FAST telescope has twice the sensitivity of the Arecibo radio telescope, as well as more than five times the speed of scanning the sky.
The frequency range that the radio telescope covers is from 70 MHz – 3 GHz. The FAST radio telescope can be focused in a direction that, together with the zenith, forms an angle of at least 40°.
Although FAST is called a spherical radio telescope with a 500-meter aperture, it is clearly not spherical in shape, and the effective diameter of its reflector (radius of curvature) is 300 meters. And while Arecibo can make full use of its 305-meter aperture when observing at the zenith, it often observes objects at an angle, where the effective aperture is only 221 meters. Because the FAST radio telescope's reflector is much deeper than Arecibo's, it expands the field of view for observations.
Yet despite FAST's superior performance, Arecibo remains a leader in some types of research. For example, studying the earth's ionosphere, studying the inner planets of the solar system, as well as carrying out precise measurements of the orbits of asteroids in the vicinity of the Earth. Similar studies are available at Arecibo Observatory due to the presence of transmitters and other special equipment that are not available on the FAST radio telescope. In addition, the latter is located 7.5° north of the Arecibo Observatory. With such a closer location of the observatory to the equator, slightly more space bodies fall into its field of view than in the field of view of FAST.
Implications for science and the public
The scientific community intends to use the FAST radio telescope to search for, capture radio emission from, and also to detect extraterrestrial signals of artificial origin.
For the first couple of years, this telescope is available only to Chinese scientists and specialists, after which it will be open to the international scientific community.
Despite the fact that in order to prevent radio interference within a radius of five kilometers, the authorities resettled more than 9 thousand residents with subsequent payment of compensation, various tourist facilities were built near the observatory, which will allow interested parties to attend excursions to the largest radio telescope in the world. For example, the Arecibo Observatory is visited annually by about 200 scientists and 90 thousand tourists from all over the world.
Telescope FAST
The 500-meter FAST radio telescope, the world's largest filled aperture telescope, has been put into operation in China. In terms of its diameter, it is second only to RATAN-600, located in Karachay-Cherkessia, which, however, does not have a filled aperture. The closest analogue of FAST is the 300-meter radio telescope at the Arecibo Observatory. Xinhua agency reports this.
The dimensions of the telescope determine its performance characteristics - sensitivity, resolution, and so on. The larger the radio telescope, the smaller or more distant objects it can detect. In terms of resolution, the absolute record holder is RadioAstron. This is a system for observing space objects using ultra-long baseline interferometry, consisting of the Spektr-R space radio telescope and various ground-based radio telescopes. Together they form an instrument equivalent to a radio telescope with a diameter of about one hundred thousand kilometers.
However, such systems have low sensitivity due to their small effective area. The overall sensitivity is determined as the geometric mean of the sensitivity of the 10-meter Spektr-R and the ground-based radio telescope operating in tandem with it. Therefore, such observations require ground-based instruments of high sensitivity. In addition, new radio telescopes expand the tools available to astronomers around the world.
The new radio telescope is located in Guizhou province and has an area of about 30 football fields. Despite the 500-meter diameter, observations will use reflector fragments with a diameter of about 300 meters - this is the effective diameter of the telescope. By this indicator, FAST is only slightly better than the Arecibo Observatory (221 meters). The 500-meter reflector will allow the telescope to have a much larger field of view.
After commissioning, the first test observations were already carried out at the telescope. According to Qian Lei, a researcher at the National Astronomical Laboratory (China), the telescope successfully detected a signal from one of the pulsars, located 1351 light years from Earth.
FAST's tasks will include tracking pulsars, studying interstellar gas, searching for complex molecules, and analyzing objects from the reionization era. Scientists expect the radio telescope to double the number of pulsars known to science. This can help in the search for gravitational wave signals in "glitches" of pulsar radiation (such observations, for example, by the NANOGrav consortium). Representatives of the RadioAstron project previously stated that FAST will be able to work in tandem with Spektr-R. The radio telescope will be tuned for the first two to three years after commissioning, after which it will become available to the international community.
Interestingly, to build the telescope, the Chinese authorities had to resettle about 9,000 local residents outside the five-kilometer zone around the telescope. Construction took place in July 2016. Next to the telescope there is an observation deck, to which access will be organized for tourist groups - up to two thousand people a day. The cost of a ticket for it will be about 3.5 thousand rubles in terms of Russian money.
Vladimir Korolev
Chinese half-kilometer telescope July 27th, 2015
Yes, we have already discussed it in detail. The diameter of the plate is 304.8 meters. But the Chinese wouldn't be Chinese if they didn't try to build something more... much more!
In the south of China, in the province of Guizhou, construction began on a new miracle of engineering - the “Spherical Radio Telescope with a 500-meter aperture.”
Photo 2. 
Like the area around Arecibo, the Chinese province of Guizhou has many karst depressions formed by water that has eroded limestone over the years. After studying satellite and aerial photography data, Rendong Nan and his colleagues from the National Astronomical Observatory of the People's Republic of China were able to find a crater with a diameter of about 800 meters, which is surrounded by mountains and located far enough from radio frequency interference.
However, the area was not completely deserted. At the very bottom of this depression there was a village, which consisted of a large family of about 80 people. Every day people had to rise to the surface: adults grazed livestock, and children hurried to school. As astronomer Di Li said, people actually had to climb the mountain every day and then go back down. Naturally, all the inhabitants of this village were resettled to the nearest city.
Photo 3. 
Construction is due to be completed in September 2016. To do this, it is necessary to extract several million cubic meters of soil in order to give the funnel a spherical shape.
Photo 4. 
Despite the fact that the designers were inspired by the Arecibo example, technology does not stand still, and FAST will have a number of fundamental differences. For example, the Arecibo antenna is made with a fixed spherical curvature, so incoming radio waves are focused above the “dish” into a line, and hanging secondary and tertiary mirrors direct the radio waves to a point where they can be processed using instruments. This results in only 211 meters of a 305 meter antenna being usable at a time.
Photo 5. 
The 500-meter FAST “dish”, consisting of 4,400 triangular-shaped aluminum panels, will independently focus the signal, without hanging mirrors. To do this, some panels are made movable so that they can form a parabolic mirror with a diameter of 300 anywhere on the 500-meter surface of the antenna. This will allow us to study a wider part of the sky. Thanks to this, FAST can simultaneously study 19 areas of the sky, while Arecibo can only cover 7 areas of the sky at a time.
Photo 6. 
“The radio telescope is like a highly sensitive ear, listening to the white noise of the cosmic background and looking for meaningful radio signals in it,” said Nan Rendong, research director of the FAST project, which is led by the National Astronomical Observatory of the Chinese Academy. Sciences (Chinese Academy of Sciences), “This process is like trying to hear the sounds of cicadas chirping against the backdrop of a raging thunderstorm. But the antenna's large size and high-quality electronics will allow us to receive even the weakest signals, allowing astronomers and SETI scientists to dig further and deeper into the history of our Universe."
“Having a radio telescope with such high sensitivity, we will be able to receive very weak signals from sources located very far in the depths of outer space,” says Wu Xiangping, director general of the Chinese Astronomical Society. “All this will allow “We must attempt to search for intelligent life far beyond the boundaries of our galaxy and explore the mysteries of the origin of the Universe.”
Photo 7. 