Technologies, prospects and hopes of Radio Astron


    The center of the Milky Way galaxy in the Spizer infrared telescope. © NASA We

    continue the conversation with the head of the laboratory of extragalactic radio astronomy of the PN Lebedev Physical Institute of the Russian Academy of Sciences Yuri Kovalev. Today we are talking about data processing technologies that allow you to obtain unique knowledge about interstellar and intergalactic space, about the Nobel potential, about relations with China, and the prospects of domestic radio astronomy.


    © polit.ru

    The RadioAstron project is a radio astronomy experiment based on the method of radio interferometry with extra-long bases (VLBI). The essence of this method is that two or more radio telescopes work as elements of one large antenna. This allows observations to be made with a very high (record) angular resolution, which depends on how far the telescopes are spaced. With ground-based observations, it is impossible to increase the size of the VLBI network over the diameter of the planet Earth. You can increase the resolution by moving one of the telescopes into space. Such a telescope was the 10-meter Russian Spectrum-R. The limitation of this method is that only bright radio sources can be observed in this way: quasars, pulsars, etc. The distance between the Earth and the spacecraft is called the “base projection” and is considered in Earth’s diameters.

    In the first part of the interview, we talked about the results achieved. Today we are talking about the future.


    - I think many will be interested in the question: is there any direction in that RadioAstron program that has potential for the Nobel Prize?

    - The question is good and correct. The problem is that the answer to it characterizes the responder to a greater extent than the project itself. Therefore, it is somewhat difficult for me. But why don’t we try to be careful on the one hand, so as not to be accused of excessive “pop music”, but on the other hand close to the topic. Attempts to map the center of our Galaxy and restore its true image, this is an obvious potential for the Nobel Prize. If we succeed ... If at least sometime the Nobel Prize is given for the most direct or least indirect discovery of a black hole ... the so-called "black hole shadow" - such a circle or crescent at a distance of several event horizons of a black hole - I predict that this will be done without taking into account The effect of the scattering spot substructure we discovered is simply impossible. Therefore, whether Radio Astron will have the Nobel Prize or not, our contribution to the Nobel Prize on this issue is obliged to enter. And it is already included in the sense that all publications of the last 1-2 years on this subject are necessarily discussing this effect, taking into account, analyzing it.

    If we talk about the prize for us, then we conducted the corresponding experiment in September 2015. The mapping of the center of our Galaxy at a wavelength of 1.3 centimeters was carried out using a space radio telescope and about twenty antennas on Earth - American, Australian, Korean, Chinese. If we succeed, after restoring the true image of the center of the Galaxy, to obtain information about the shadow of a black hole, then this is obviously the potential for the Nobel Prize.


    Modeling of various options for the image of a black hole.

    - That is, in fact, you can see a black hole? At least what you can see in it at all.

    - Yes, this is what the project manager Nikolay Semenovich Kardashev said before launch. I was more conservative in the predictions ... Mostly, I tried to evaluate the minimum "guaranteed" list of results that RadioAstron is able to give. Nikolai Semenovich always looks broadly at problems and, often, with his genius, I’m not afraid of the word, he can predict things that, to many others, seem too bold. He said before the launch of Spectra-R into space that Radio Astron would see black holes.

    We tried to do this while observing the center of the galaxy in the constellation Virgo (Virgo A or M 87). Technically, we have such an opportunity with an existing orbit and a working receiver at the shortest wavelength of 1.3 centimeters. We should have been lucky in the sense that the conditions for absorption (sometimes also called synchrotron self-absorption) and the scattering of radiation should have been soft enough to see the shadow of a black hole. Failed. It is possible that due to synchrotron self-absorption. It is clear where to move - to shorter waves, at which these effects are weaker.


    M 87 in the shooting of the Hubble Space Telescope. The relativistic jet from the center of the galaxy (c) NASA is clearly visible

    In the center of the galaxy, they were not going to work, because they knew about dispersion in dense clouds. Our discovery of the scattering substructure effect gave us hope to restore the true image of the center of the Galaxy by taking this effect into account. Maybe we will succeed. This will be a result close to the level of the Nobel Prize ... Again, if you are optimistic, if we are lucky. We are working in this direction, the first results are positive, insanely interesting and a large number of articles on this subject have already been published. In any case, RadioAstron significantly advanced world science in this direction, even if the prize did not go to us.
    (Links: one , two , three , four , five. All publications on the RadioAstron project: here ).


    Modeling the variability of the refraction scattering substructure for a ring to understand what to expect for a “black hole shadow”. The apparent motion is associated with the movement of the turbulent cloud in front of the ring. (c) Michael Johnson (Harvard CfA).

    As for other areas, it is more difficult to predict. There are a lot of interesting results on quasars, however, as far as they have potential for the Nobel Prize, it’s quite difficult for me to judge, I will be careful here.

    - What do you think, the data of Radio Astron, the results of its work will somehow have a significant adjustment or influence on the change in the modern cosmological picture of the Universe?

    - To be realistic, it is unlikely. Cosmological tasks did not confront the RadioAstron project. Perhaps the only direction that could potentially contribute to the understanding of dark energy is the study of megamasers [ starburst clouds in other galaxies ] due to the possibility of an independent estimate of the distances to them.

    - Back to the Earth. You mentioned the participation of Chinese scientists in the project. They built a new telescope. Will it be involved in the RadioAstron program?



    - Undoubtedly, when it starts working in the interferometry mode with extra-long bases (VLBI), it can become an element of the ground-space interferometer, and we will definitely use it in the RadioAstron project. I have absolutely no doubt. We work with all the largest radio telescopes in the world that conduct experiments on VLBI astrophysics. Radio Astron does not impose any special requirements on ground-based telescopes to work in its own mode. Moreover, speaking about China, we have a memorandum of understanding between the Astro Space Center of the Lebedev Physical Institute and the Shanghai Observatory. Obviously, any radio telescope will be honorably politically and scientifically interested in participating in observations with Radio Astron. There have never been projects of this class in centimeter and decimeter space radio astronomy, and in the near future, unfortunately, not expected. For example, it was our success that led to the fact that the Chinese project of the ground-space interferometer, unfortunately, did not happen - this is my reading of the situation. The Chinese Space Agency did not support him. We are the only chance of ground-based telescopes to participate in such experiments in the coming years. And I hope that the FAST telescope - a 500-meter telescope - will introduce an interferometric observation mode as soon as possible in order to work with Radio Astron. There are many examples of telescopes that started working with us being just built and launched. For example, a 65-meter telescope with an active surface near Shanghai, a 64-meter telescope with an active surface in Sardinia. Immediately after returning to service, the 32nd telescope, restored by Latvian colleagues, began to work with us in Irben. For example, it was our success that led to the fact that the Chinese project of the ground-space interferometer, unfortunately, did not happen - this is my reading of the situation. The Chinese Space Agency did not support him. We are the only chance of ground-based telescopes to participate in such experiments in the coming years. And I hope that the FAST telescope - a 500-meter telescope - will introduce an interferometric observation mode as soon as possible in order to work with Radio Astron. There are many examples of telescopes that started working with us being just built and launched. For example, a 65-meter telescope with an active surface near Shanghai, a 64-meter telescope with an active surface in Sardinia. Immediately after returning to service, the 32nd telescope, restored by Latvian colleagues, began to work with us in Irben. For example, it was our success that led to the fact that the Chinese project of the ground-space interferometer, unfortunately, did not happen - this is my reading of the situation. The Chinese Space Agency did not support him. We are the only chance of ground-based telescopes to participate in such experiments in the coming years. And I hope that the FAST telescope - a 500-meter telescope - will introduce an interferometric observation mode as soon as possible in order to work with Radio Astron. There are many examples of telescopes that started working with us being just built and launched. For example, a 65-meter telescope with an active surface near Shanghai, a 64-meter telescope with an active surface in Sardinia. Immediately after returning to service, the 32nd telescope, restored by Latvian colleagues, began to work with us in Irben. it was our success that led to the fact that the Chinese project of the ground-space interferometer, unfortunately, did not happen - this is my reading of the situation. The Chinese Space Agency did not support him. We are the only chance of ground-based telescopes to participate in such experiments in the coming years. And I hope that the FAST telescope - a 500-meter telescope - will introduce an interferometric observation mode as soon as possible in order to work with Radio Astron. There are many examples of telescopes that started working with us being just built and launched. For example, a 65-meter telescope with an active surface near Shanghai, a 64-meter telescope with an active surface in Sardinia. Immediately after returning to service, the 32nd telescope, restored by Latvian colleagues, began to work with us in Irben. it was our success that led to the fact that the Chinese project of the ground-space interferometer, unfortunately, did not happen - this is my reading of the situation. The Chinese Space Agency did not support him. We are the only chance of ground-based telescopes to participate in such experiments in the coming years. And I hope that the FAST telescope - a 500-meter telescope - will introduce an interferometric observation mode as soon as possible in order to work with Radio Astron. There are many examples of telescopes that started working with us being just built and launched. For example, a 65-meter telescope with an active surface near Shanghai, a 64-meter telescope with an active surface in Sardinia. Immediately after returning to service, the 32nd telescope, restored by Latvian colleagues, began to work with us in Irben. that the Chinese project of the space-space interferometer, unfortunately, did not happen - this is my reading of the situation. The Chinese Space Agency did not support him. We are the only chance of ground-based telescopes to participate in such experiments in the coming years. And I hope that the FAST telescope - a 500-meter telescope - will introduce an interferometric observation mode as soon as possible in order to work with Radio Astron. There are many examples of telescopes that started working with us being just built and launched. For example, a 65-meter telescope with an active surface near Shanghai, a 64-meter telescope with an active surface in Sardinia. Immediately after returning to service, the 32nd telescope, restored by Latvian colleagues, began to work with us in Irben. that the Chinese project of the space-space interferometer, unfortunately, did not happen - this is my reading of the situation. The Chinese Space Agency did not support him. We are the only chance of ground-based telescopes to participate in such experiments in the coming years. And I hope that the FAST telescope - a 500-meter telescope - will introduce an interferometric observation mode as soon as possible in order to work with Radio Astron. There are many examples of telescopes that started working with us being just built and launched. For example, a 65-meter telescope with an active surface near Shanghai, a 64-meter telescope with an active surface in Sardinia. Immediately after returning to service, the 32nd telescope, restored by Latvian colleagues, began to work with us in Irben. did not happen - this is my reading of the situation. The Chinese Space Agency did not support him. We are the only chance of ground-based telescopes to participate in such experiments in the coming years. And I hope that the FAST telescope - a 500-meter telescope - will introduce an interferometric observation mode as soon as possible in order to work with Radio Astron. There are many examples of telescopes that started working with us being just built and launched. For example, a 65-meter telescope with an active surface near Shanghai, a 64-meter telescope with an active surface in Sardinia. Immediately after returning to service, the 32nd telescope, restored by Latvian colleagues, began to work with us in Irben. did not happen - this is my reading of the situation. The Chinese Space Agency did not support him. We are the only chance of ground-based telescopes to participate in such experiments in the coming years. And I hope that the FAST telescope - a 500-meter telescope - will introduce an interferometric observation mode as soon as possible in order to work with Radio Astron. There are many examples of telescopes that started working with us being just built and launched. For example, a 65-meter telescope with an active surface near Shanghai, a 64-meter telescope with an active surface in Sardinia. Immediately after returning to service, the 32nd telescope, restored by Latvian colleagues, began to work with us in Irben. We are the only chance of ground-based telescopes to participate in such experiments in the coming years. And I hope that the FAST telescope - a 500-meter telescope - will introduce an interferometric observation mode as soon as possible in order to work with Radio Astron. There are many examples of telescopes that started working with us being just built and launched. For example, a 65-meter telescope with an active surface near Shanghai, a 64-meter telescope with an active surface in Sardinia. Immediately after returning to service, the 32nd telescope, restored by Latvian colleagues, began to work with us in Irben. We are the only chance of ground-based telescopes to participate in such experiments in the coming years. And I hope that the FAST telescope - a 500-meter telescope - will introduce an interferometric observation mode as soon as possible in order to work with Radio Astron. There are many examples of telescopes that started working with us being just built and launched. For example, a 65-meter telescope with an active surface near Shanghai, a 64-meter telescope with an active surface in Sardinia. Immediately after returning to service, the 32nd telescope, restored by Latvian colleagues, began to work with us in Irben. who started working with us being just built and launched. For example, a 65-meter telescope with an active surface near Shanghai, a 64-meter telescope with an active surface in Sardinia. Immediately after returning to service, the 32nd telescope, restored by Latvian colleagues, began to work with us in Irben. who started working with us being just built and launched. For example, a 65-meter telescope with an active surface near Shanghai, a 64-meter telescope with an active surface in Sardinia. Immediately after returning to service, the 32nd telescope, restored by Latvian colleagues, began to work with us in Irben.


    FAST Radio Telescope (China) (c) Fast.bao.ac.cn

    - Do the dimensions and capabilities of the Chinese FAST promise an increase in the quality of observations?

    - Of course they promise. Here is such a beautiful situation: the sensitivity of the interferometer is equal to the root of the product of the sensitivities of the two telescopes that form it. You cannot launch a plate of 500 meters into space, in space you cannot cool amplifiers for very low temperatures for many years ... Either you cool for a short time, or you send “warm” receivers. We have a 10-meter space telescope, it is the largest telescope in space, we even have a certificate of the Guinness Book of Records. Receivers at Radio Astron are cooled passively. If you have a larger telescope on Earth, then it gives you the opportunity to improve the sensitivity of the interferometer as a whole. Today, the largest telescope that works with ours is the 300-meter FAST analogue, the Arecibo antenna in Puerto Rico, USA. Arecibo understands we complement each other perfectly, therefore observations with RadioAstron for the Arecibo telescope are one of the highest priorities. We get the opportunity to study weaker cosmic signals, a larger number of objects further away, as well as more subtle effects, including the effect of the scattering spot substructure and much more.

    - I think many will be interested in where and how the processing of data received by Radio Astron takes place. What capacities?

    - Yes, let's talk about it. During processing, the following occurs. Suppose we are conducting a typical Radio Astron experiment. Usually from 3 to 30 radio telescopes operate on Earth, as well as the Spectrum-R space telescope. At the same time, up to hydrogen frequency standards, observations are made. [The hydrogen frequency standard is ultra-precise atomic clocks - approx.] Accordingly, ground-based telescopes record data in place. The spacecraft dumps in real time to Earth through tracking and collection stations in Pushchino (Moscow region) and Green Bank (West Virginia, USA). Then this data is reduced to the center of correlation in the usual electronic way, that is, transmitted over the Internet. Dedicated channels, in fact.

    The first processing step is the so-called “correlation processing”. It is conducted on one of the three correlators. These are computer clusters with a hundred or two cores. They are used to correlate all data streams recorded from each telescope with each other. As a result, if very simplified, at the output we get the value of the correlation coefficient depending on the time between each pair of telescopes.


    Photo of a part of the cluster used to correlate Radio Astron data at the Lebedev Physical Center. (c) ACC LPI

    The second step is already “post-correlation processing”, when we remove and correct all the effects that the measurement system — the interferometer, and the Earth’s atmosphere — introduced into the data. We compensate for the phase delay of the signal at each telescope. The phase also deteriorates, passing through the atmosphere, the ionosphere, the troposphere of the Earth ... Imperfect clocks on each telescope, delays in electronics. This is completely normal, there is no problem, this is a real experiment. Something perfect happens only on paper, but in life you need to calibrate all these effects. We translate the amplitude from the internal units of the electronics used to physical units. At the output, we get a complex signal with corrected, or, correctly speaking, calibrated amplitude and phase. This is the second processing step.

    Next is the analysis of the data depending on which experiment we conducted. There are very different types of analysis. If you are building an image of a quasar, then this is the so-called "hybrid mapping". From the set of received data, we restore the image of the object. Spectral analysis can be carried out if you are involved in spectroscopy, study a maser, respectively, you are looking for a spectral line in the data. Engaged in pulsars - you need to extract impulses from the entire data stream. This is the last step. We will call "post-correlation analysis."

    Now where are they held. As I said, the first step - correlation - is carried out on three correlators. One is located in Moscow at the LPI Astro Space Center. This is the main correlator of the RadioAstron project. It processes about 85% of the data. The remaining about 15% are correlated in Bonn, at the Max Planck Institute for Radio Astronomy, and at the Joint Institute for VLBI in Europe, the Netherlands. These three correlators are different, hardware, correlation programs are different. One of our prides is that the outputs of these correlators coincide. If you process the same experimental data on these three super-computers, the result will be exactly the same. It's very nice. Naturally, it was extremely important during the first year to make sure that we all agree with each other and independent data analysis,

    Post-correlation processing and analysis is carried out by the research groups of the project, which include co-authors from about twenty countries of the world. Some of their tasks require super-computers, some fairly powerful workstations, some can be done on a laptop.

    - In your opinion, how much longer can RadioAstron work?

    -A frequent question, if I were a politician, I said, “On the basis of the decision of the state commission, the Russian Space Agency extended the RadioAstron project until the end of 2018.” The true truth. The decision was made in the spring of 2016. As for the technical capabilities ... Yes, we see the degradation of equipment on board. However, we and Lavochkin’s NGO all systems are duplicated or tripled. Some today have remained in one or two copies. From the very beginning of the launch of the space project into space, we live with the understanding that today may be our last day, or maybe we will live for many more years.


    "Spectrum-R" in the assembly shop (c) NPO Lavochkina

    - Regarding degradation. Can we say that childhood diseases have passed, and now everything is working as usual?

    - This we could say in the first year of flight. There were childhood diseases, both on Earth and in space. I can tell you the date we finished with the last serious childhood illness. March 15, 2012. Since then, we have been working normally in all modes. Four wavelength ranges, total intensity and polarization, masers, pulsars, quasars - these are all different modes. Multi-frequency mode in a wide range from 18 to 25 GHz.

    Working in the normal mode, it happens that some equipment fails. NPO Lavochkina either switches to spare systems or solves the problem. Today, the characteristics of the Spectrum-R apparatus and its ability to solve scientific problems are at about the same level as in the spring of 2012, when we entered full-fledged combat mode. We have certain new limitations. For example, the situation with gyrodynes . But until now, nothing has significantly affected the ability to continue the implementation of the scientific program, which is formed every year on the basis of an open call for proposals.

    - Quite a poppy question: Can we find aliens with the help of Radio Astron?

    - Aliens can be found, as you understand with glasses, if they land next to your house and go into your apartment. Accordingly, we can. For example, if we see a “cosmic miracle” that cannot be explained by any modern laws of physics.

    - If we using the Radio Astron from any distance observed the Earth, could we determine its certain abnormal behavior? Including in the radio range. If they could, then at what distance?

    - I do not think that you need RadioAstron for this, since the Earth is very small and in any case would look like a point. In this sense, you need a very large and, accordingly, sensitive telescope, such as the same FASTa. He is one of the prototypes of the Square Kilometre Array (a telescope project with a collecting surface the size of a square kilometer). SKA is currently under construction in the southern hemisphere, part in Africa, part in Australia. In fact, if you build a huge very highly sensitive telescope, then you can register the emission of organic molecules from distant planets. Accordingly, life, although not reasonable. This task is facing many ground-based telescopes. The same space Millimetron that we are developing will have the necessary angular resolution to see the shadow of a black hole, it will work at high frequencies, to defeat the takeover problem. And on the third hand, it will have high sensitivity and work at radio frequencies that will allow us to study the radiation of organic molecules.

    - My question was not so much about organic matter, but about our business activities. For example, radars and the like.

    - The Spectrum-R itself, a 10-meter mirror in space, is difficult to compete with the sensitivity of ground-based telescopes to solve this problem. As for interferometry ... Suppose you find some suspicious candidate that you need to investigate with extreme angular resolution, while the sensitivity of the interferometer is enough. Then RadioAstron can connect and find anomalies. You see, poppy question is partially poppy answer. Yes, if we see anomalies, we can discover aliens. So far, we do not see such anomalies in the Universe.

    - You began to answer a question I have not yet asked about Millimetron and about the prospects for Russian radio astronomy in the coming years. What do you expect to expect? What work is currently underway for the future?


    The project of the space radio telescope "Spectrum-M" (Millimetron) (c) ACC LPI

    - Are we talking only about space or about the Earth too?

    -Maybe about the Earth, we are talking about science in principle.

    -Good. I'll start from the earth. Over the past year, an interdepartmental working group of experts collected and analyzed proposals for the development of ground-based astronomical infrastructure (telescopes) in the Russian Federation. It was about building new ones or completing construction work begun. Discussions were conducted widely and openly. A group of experts formed recommendations with ratings and submitted them to the relevant executive authorities of Russia. As for radio astronomy, one international project and two Russian ones reached the final. International project - Russia's participation in Square Kilometre Array(SKA). The recommendation was as follows: SKA is important, great, participation in this project is the future of our country. At the same time, Russia's participation in SKA was recommended after a positive decision to participate in the European Southern Observatory (ESO). The reason is simple - the number of Russian astronomers who can use ESO resources is much more than those who can use SKA.

    Among Russian projects in the field of radio astronomy, two are noted. The first is the completion of construction on the Suffa plateau in Uzbekistan of a 70-meter active surface mirror.


    Canned construction of a radio telescope on the Suffa plateau (Uzbekistan). (c) A. Zharkov

    II - construction of a new type of long-wave digital radio telescope based on the experience of the Pushchino Observatory.

    Why were these projects selected, along with the modernization of the RATAN-600 at the SAO RAS? Now long and short waves have received a serious push forward thanks to the introduction of digital methods of radio astronomy and the development of technology. And with regard to short waves, the most serious example of the latest breakthroughs is the ALMA interferometer located in Chile. Long Waves - LOFAR in the Netherlands.

    Millimetron, in this sense, is a similar step in the dynamics of the development of millimeter and submillimeter astronomy. Millimetron can expand the modern capabilities available thanks to ALMA. The latter is observed only in certain frequency ranges due to the partial opacity of the atmosphere. Millimetron, being in space, wins. He can observe in the entire range of millimeters and submillimeters. Its sensitivity will be increased due to the heat shield and active cooling of the mirror surface.


    A mock-up of the Millimetron heat shield in the assembly shop of the ISS Reshetnev (s) ISS Reshetnev / ORKK

    At the same time, the Millimetron, as a ground-space interferometer, will provide absolutely beyond the range angular resolution while minimizing the problems of scattering and self-absorption of radiation. This is the next step after Radio Astron.

    As for long waves, a lot is known about LOFAR . Russia is lagging behind so far. We do not participate in LOFAR, but the long-wavelength radio astronomy is extremely interesting. We - radio astronomers - were able to overcome two problems. One is the problem associated with the ionosphere and with terrible scattering, actually spoiling the phase of the incoming radio emission. And on the other hand there are nightmares. New technologies for interference cleaning are actively developed and implemented, allowing us to clean the data from interference in automatic mode, losing about 10% of the data.

    You can also mention that, on the proposal of the Space Research Institute, we are discussing the possibility of building an ultra-long-wave radio telescope on the moon. If Russia, of course, will go to the moon.

    On the importance of the moon for Russian and world radio astronomy, we will continue the discussion in the next issue, stay tuned.

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