Radio astron

The main scientific goal of the mission is the study of astronomical objects of various types with an unprecedented resolution of up to millionths of a second of arc. The permission achieved with the help of the Radioastron project will allow you to study:

• relativistic jets , as well as the immediate vicinity of supermassive black holes in active galaxies ,
• the structure and dynamics of star formation regions in our Galaxy according to maser and megamaser radiation;
• neutron stars and black holes in our Galaxy - a structure based on measurements of fluctuations in the visibility function, proper motions and parallaxes ;
• structure and distribution of interstellar and interplanetary plasma according to fluctuations of the visibility function of pulsars ;
• construction of a high-precision astronomical coordinate system ;
• building a high-precision model of the Earth’s gravitational field .

Plasma-F Experiment

In addition to the equipment for the main mission, on board the satellite are devices for the Plasma-F experiment ^[6] . The instrument weighs about 20 kg and can measure the flow of solar wind with a time resolution of 30 milliseconds (this is comparable to the performance of satellites such as “ACE” (Advanced Composition Explorer) and “ Wind ”). Measurements of the speed, temperature and concentration of the solar wind have a time resolution of 1.5 seconds ^[7] .

The tasks of the Plasma-F scientific experiment are monitoring of the interplanetary medium in order to make forecasts of “ space weather ”, studying the turbulence of the solar wind and magnetic field in the range of 0.1 - 30 Hz, and studying the processes of acceleration of cosmic particles . The satellite is located outside the Earth’s magnetosphere for several days, which makes it possible to observe the interplanetary medium, and then very quickly passes through all layers of the magnetosphere, so that it can be monitored.

The basis of the project is a terrestrial-space radio interferometer with an extra-long base , consisting of a network of ground-based radio telescopes and a space radio telescope (SRT) ^{[2] [3]} installed on the Russian Spectrum-R spacecraft. The creator of the Spectrum-R apparatus is the Lavochkin NGO ^[8] , the chief designer is Vladimir Bobyshkin ^[7] .

The essence of the experiment is the simultaneous observation of one radio source by space and ground-based radio telescopes. Records obtained with radio telescopes are provided with time stamps from high-precision atomic clocks , which, together with accurate knowledge of the position of the telescopes, allows you to synchronize the records and get the interference of signals recorded on different telescopes. Due to this, independently operating telescopes make up a single interferometer, the angular resolution of which is determined by the distance between the telescopes, and not by the size of the antennas ( VLBI method).The SRT moves in an elliptical orbit with an apogee height of about 340 thousand km ^[9] , comparable with the distance to the Moon , and uses lunar gravity to rotate its orbit plane. High resolution when observing radio sources is provided due to the large arm of the interferometer, equal to the height of the apogee of the orbit.

The main parameters of the ground-space interferometer of the Radioastron project ^[10] :

The width of the interference lobe determines the angular resolution of the radio interferometer, that is, for example, at a wavelength of 92 cm , Radioastron will be able to distinguish two sources of radio emission located at an angular distance of about 540 μs or more from each other, and at a wavelength of 6.2 cm - even closer ( 37 μs and more) ^[11] .

The interferometer requires knowledge of the position of the spacecraft with high accuracy. According to the technical specifications, the required accuracy is: several hundred meters in distance, speed - not worse than 2 cm / s , acceleration - 10 ⁻⁷ m / s² . To ensure these requirements are used ^[4] :

• radiometric measurements of speed and distance using a 64-meter control telescope at the Bear Lakes Space Communication Center , a 72-meter mirror at the East Center for Long-Range Space Communication (Ussuriysk);
• Doppler methods of measuring speed using stations in Pushchino and in the USA;
• laser ranging
• optical methods for determining the position of background stars;
• interometric methods.

Space Radio Telescope

A space radio telescope with a receiving parabolic antenna with a diameter of 10 meters was launched into the high-apogee orbit of an Earth satellite up to 350 thousand km high as part of the Spektr-R spacecraft ^[12] . It is the world's largest space telescope, which was noted in the Guinness Book of Records ^[13] .

In the Radioastron project, the use of a radio telescope in a highly elliptical orbit makes it possible to obtain an interferometer with a base significantly exceeding the diameter of the Earth. An interferometer with such a base allows obtaining information on the structure of galactic and extragalactic radio sources at angular scales of the order of 30 microseconds and even up to 8 microseconds of an arc for the shortest wavelength of the project ( 1.35 cm ) when observing at the maximum base length.

Equipment

The total scientific payload is approximately 2600 kg . It includes the mass of a drop-down parabolic antenna with a diameter of 10 m ( 1500 kg ) and the mass of an electronic complex containing receivers, low-noise amplifiers , frequency synthesizers , control units, signal converters, frequency standards, a highly informative scientific data transmission system (about 900 kg ). The mass of the entire satellite launched into orbit using the Zenit-2SB launch vehicle with the Frigate-2SB booster block is about 3850 kg ^[14]

The total power supply of the system is 2600 W , of which 1150 W is used for scientific instruments. While in the shade, the battery pack of the device allows you to work for about two hours without power from solar panels ^[7] .

Antenna

The antenna of the space radio telescope consists of 27 petals . When launching into the target orbit, the antenna was in a folded (similar to an umbrella) state. After reaching the target orbit, the mechanical opening of the radio telescope antenna was performed ^[7] . The antenna is made of carbon fiber ^[15] .

Communication

Before the failure of the last set of command radio receiver in January 2019, the largest in Russia P-2500 antenna systems (diameter 70 m ) in the Eastern Center for Long-Range Space Communication and TNA-1500 (diameter 64 m ) in the Moscow Space Communication Center near Moscow used the two-way communication sessions. Bear Lakes . " At short distances to the SRT (up to 100 thousand km ), the NS-3.7 antenna was used, located in MCC-L in the NPO named after S. A. Lavochkina.

Communication with the Spectrum-R device was possible in two modes. The first mode is two-way communication, including the transfer of commands on board and receiving telemetric information from it.

The second communication mode is the reset of radio interferometric data through a highly directional antenna of a highly informative radio complex (VIRK). Data had to be transmitted in real time ^[4] , since a large-capacity storage device was not part of the telescope. In 2015, a radio tracking station was used to receive radio interferometric data, created on the basis of the 22-meter RT-22 radio telescope in Pushchino, Moscow Region. The flow of information collected by the telescope was 144 megabits per second. To enable interferometric observations when the spacecraft is not visible to the tracking station in Pushchino, Roscosmos funded the creation of additional tracking stations outside of Russia: in the USA and South Africa ^{[16] [17]} . Since August 2013, a station was commissioned in Green Bank (USA, West Virginia) ^[4] .

The project was launched in 1979-1980, with the approval of Leonid Ilyich Brezhnev , he survived the period of stagnation and the economic downturn of the 1990s .

In the second half of the 2000s, the project was significantly revised for approximately 5 years ^[4] .

Launch

The launch of the SRT was performed on July 18, 2011 at 6:31 Moscow time from the 45th site of the Baikonur Cosmodrome with the Zenit-2SLB80 launch vehicle with the Frigate-SB booster block ^[18] .

On July 18, 2011 at 10:06 Moscow time, the Spektr-R spacecraft reached the target highly elliptical orbit with parameters ^[19] :

• perigee - 600 km ;
• apogee - 330 thousand km ;
• circulation period - 8.2 days ;
• the initial inclination is 51.3 °.

In the morning of July 22, a command was issued to open the antenna, after about 10 minutes a signal was received that the engine responsible for the opening had stopped moving. However, no confirmation signal was received. It was decided on the night of July 22-23 to deploy the satellite so that the sun evenly warmed up the antenna drive structure. In the morning, a second command was issued to open the telescope, and then to fix the petals. After that, signals were received confirming the successful fixation of each of the 27 antenna lobes . ^[four]

Under the influence of lunar gravity, the orbit plane rotates continuously, which allows the observatory to scan space in all directions ^[4] . Over the planned time of work ( 5 years ), the attraction of the moon will raise the apogee of the radio telescope to an altitude of 390,000 km ^[20] .

When moving in orbit, the spacecraft passes through the radiation belts of the Earth , which increases the radiation load on its devices. The service life of the spacecraft is about 5 years ^[21] . According to ballistic calculations, MCT will fly for 9 years , after which it will enter the dense atmosphere and burn out ^[22] .

In March 2012, an orbit correction was carried out, which ensured a gravitationally stable regime for the next 10 years ^[4] .

At the time of its entry into orbit, the space radio telescope mounted on board the Russian Spectrum-R spacecraft was the most remote radio telescope ^[20] .

Getting started

After opening the mirror of the receiving antenna, the SRT took about three months before the start of observations to synchronize with terrestrial radio telescopes ^[23] .

Upon completion of the verification of all systems of the apparatus, the stage of scientific research has begun. On Earth, two hundred-meter radio telescopes are used as synchronous radio telescopes in Green Bank ( West Virginia , USA ) and Effelsberg ( Germany ), as well as the famous Arecibo radio observatory ( Puerto Rico ) ^[20] . A terrestrial-space interferometer with such a base provides information on the morphological characteristics and coordinates of galactic and extragalactic radio sources with a width of interference lobes up to 8 microseconds of an arc for the shortest wavelength of the project ( 1.35 cm ).

By August 5, the entire Plasma-F complex ^[24] was turned ^on and the first measurements ^[25] were obtained.

September 27, "Spectrum-R" first conducted test observations of a space object - the remnant of supernova Cassiopeia A. Successfully conducted observations by scanning in two orthogonal directions in the ranges of 92 and 18 cm in two circular polarizations.

On October 29 and 30, 2011, a radio telescope made observations of the W3 (OH) maser in the constellation Cassiopeia ^[26] .

On November 14–15, 2011, simultaneous observations in the interferometric mode were successfully performed on SRT Spectrum-R, three Russian radio telescopes forming the Quasar radio interferometric network (RT-32 Svetloye , RT-32 Zelenchukskaya , RT-32 Badary ) and the Crimean RT-70 Evpatoria radio telescope. The purpose of the observation was the pulsar PSR B0531 + 21 in the Crab nebula , quasars 0016 + 731 and 0212 + 735 (the German 100-meter radio telescope in Effelsberg ^[27] was additionally used to study the quasar 0212 + 735), as well as sources of maser radiation W3 (OH ) ^[28] .

About 100 scientific experiments are carried out per month ^[4] .

The total costs of the Radioastron program are very high ^{[ how much? ]} , therefore, an international committee was formed to draw up a scientific program; An application for observational time can be submitted by any scientist, the committee selects applications with the strongest scientific level, offering the most interesting scientific ideas. ^[four]

In July 2016, the fourth year of the open observation program began; 11 projects were selected for implementation during this period ^[29] :

The leaders of applications accepted for implementation are three representatives of Russia, two from the Netherlands and one from Spain, Japan, South Africa and the USA. Co-authors of the applications represent 19 countries in the amount of approximately 155 people. The largest number of co-authors of applications is from Russia, followed by the United States, Germany, Spain, the Netherlands, Australia, Italy and others.

- Press release of the Physics Institute. Lebedeva RAS

Lost Communication

Since January 10, 2019, communication with the satellite has been lost; at the same time, the satellite’s warranty period expired in 2014 (it was originally planned to complete the work of Spectrum-R in 2016, but it was extended until the end of 2019) ^{[30] [31]} . January 12, it became known that the radio telescope on the Spektr-R spacecraft stopped working on receiving command data, but at the same time continued to send information to Earth ^[32] . The project’s supervisor, corresponding member of the Russian Academy of Sciences, Yuri Kovalev, explained that the “Spectrum-R” works only on commands from the Earth: before each session, an observation program is put on board and a signal is sent to turn on the transmit-receive antenna; Now such a team does not go on board the device, which is transferred to the “home position”, in this state the solar batteries continue to supply power, but other parts of the satellite are no longer exposed to solar radiation and are cooled ^[33] . There is still hope for a restoration of communication, communication sessions are being conducted in an attempt to establish the situation, but if the spacecraft cannot reconnect and begin to transmit control commands, the satellite and telescope will be completed. By indirect indications, Spectrum-R is fully operational, with the exception of radio equipment that receives commands from the Earth; in its current state, it can exist until September 2019, thanks to the emergency orientation program, which operates in the absence of external commands ^[34] . The last signal from Spectra-R was received on February 5 ^[35] . On February 15, 2019, at a meeting of the State Commission of Roscosmos , it was decided to transfer the device under control to the manufacturer - NPO named after Lavochkin - for further work on establishing communication with the satellite. The work was planned for the period until May 15, after which a decision was made on the fate of the “Spectrum-R” ^[36] .

On May 30, 2019, a meeting of the State Spectrum-R flight test commission was held. The State Commission heard reports from representatives of the rocket and space industry and the scientific community and decided to complete the Spectrum-R project ^[37] .

For the first year of operation (on July 18, 2012) on the ground-space interferometer of the Radioastron project, consisting of CMT and ground-based telescopes, observations were made of 29 active galactic nuclei, 9 pulsars ( neutron stars ), 6 sources of maser lines in the regions of star formation and planetary systems ^[38] .

On October 9, 2012, an international group of active galactic nucleus researchers obtained the first image of a rapidly changing active galaxy 0716 + 714 at a wavelength of 6.2 cm from observations of the Radioastron ground-space interferometer in conjunction with the European VLBI network ^[39] .

One of the main studied types of objects is quasars . With the help of the Radioastron project, it was possible to measure the width of the beginning of the relativistic jet. It turned out to be approximately 1 St. year , this information is actively used to develop models for the formation of such jets ^[4] .

Another result was the measurement of the brightness of relativistic jets of quasars. Terrestrial radio telescopes are limited by a certain magnitude of brightness and do not allow to determine whether the real brightness is equal to it or more. The data obtained from more than 60 quasars made it possible to establish that the brightness of these jets significantly exceeds the previous representations. This requires a major restructuring of existing quasar device models. It was previously believed that relativistic electrons emit mainly in jets. This model does not allow to obtain the observed brightness. One of the new models may be the model of a jet consisting of protons accelerated to relativistic velocities, but then the question arises of the mechanism of proton acceleration to such high energies. Perhaps this problem is related to the problem of the source of high-energy cosmic rays ^[4] .

Observation of the spectrum of pulsars instead of the expected fairly smooth picture gave a number of small peaks. This requires a revision of the theory of the interstellar medium . One of the explanations may be compact turbulence zones, leading to distortion of electromagnetic radiation passing through them ^[4] .

When observing a water megamaser in the galaxy M 106 in the 1.3 MHz band with a baseline of 340 thousand km (together with a ground-based radio telescope in Medicina, Italy), an absolute record of angular resolution in astronomy was achieved - 8 microseconds of an arc (at about this angle, when observing from the Earth, a ruble coin lying on the surface of the Moon will be visible) ^[40] .

Strong scattering of radio emission by interstellar plasma was discovered ^[5] .

In 1979, a radio observatory with the first space radio telescope KRT-10 was created at the Salyut-6 station ^[41] .

In 1997, JAXA (Japan Aerospace Research Agency) launched the HALCA radio telescope with a diameter of 8 meters into an orbit about 10 times lower than the Spektr-R orbit. The device successfully worked until 2005.

China has plans to launch two spacecraft similar to Spectrum-R, while the achievements of the Russian project are actively used. ^[four]

• SNAP (satellite telescope)
• Halca
• Astron
• Millimetron
• Spectrum UV
• Spectrum RG

• Official site of the Radioastron project
• Radioastron is preparing for the first observations , Astronet - a detailed article about the entire project
• Radioastron overcame difficulties , Astronet, 09/23/2011
• Russia has a telescope “superior to the Hubble”
• The Radioastron Project and Space Radio Astronomy
• Radioastron is a radio telescope much larger than the Earth. Scientific program , Physics-Uspekhi 179 1191 (2009)
• Radioastron: A Look Into the Universe. The television plot of the Roscosmos television studio
• "Spectrum-R" - a window into the Universe
• Video of launch of Zenit-3M LV with Spektr-R
• RadioAstron - video builds and checks
• Radioastron began work
• Radioastron: Uncover Secrets of the Universe - Television plot of Roscosmos television studio
• Popular science video lecture by the head of the scientific program of the project: Kovalev Yu. Yu. RadioAstron and surprises of the Universe (neopr.) . "Tribune of the scientist . " Moscow Planetarium (February 26, 2014). Date of treatment January 26, 2015.