The existence of continuous cooling and heating processes is an important condition governing the behavior of the solar corona, which is characterized by temperatures of several million Kelvin. These processes can be significantly influenced by small-scale coronal formations, which largely determine the thermal balance of the corona and solar-wind disturbances. High-sensitivity observations of polarized radiation allow us to evaluate the complex structure of magnetic fields that accumulate the energy necessary to excite coronal eruptions, bursts and flares. However, at high altitudes the corona becomes optically thin, and observations of it pose a major challenge, requiring the use of instruments with a large effective area. Many researchers note that the emerging field of coronal magnetometry is hard to develop due to the fact that experimental observations in optical range are limited by the low plasma density in the corona, high temperature, and insufficient sensitivity of the instruments. In contrast, higher sensitivity is achievable in the radio frequency range. In particular, the 1–3 GHz range is optimal for detecting very weak coronal structures of emerging activity, despite limitations in spatial resolution. To carry out radio requency observations of the corona on the RATAN-600 large reflector-type radio telescope, a wide-range spectrometer in the range of 1–3 GHz was created. It has continuous coverage of the entire frequency range with maximum frequency and time resolutions, as well as high sensitivity to radiation flux. The results of the first series of observations of weak coronal structures are presented, and their interpretation in terms of their effect on thermal processes in the corona is discussed.

When observing the Sun with RATAN-600 radio telescope using a spectropolarimetric complex in the range 1–3 GHz, as well as when observing coronal rain, absorption in the radio emission was discovered in the spectral region 1.5–1.65 GHz in active solar regions located under a cold filament or on the limb under a prominence. The observed line structure corresponds to the hyperfine splitting frequencies in the ground state of X2Π3/2 hydroxyl (OH) 1612–1720 MHz. When the observed active region passes through the knife-shaped beam pattern of the telescope antenna, the absorption band shifts in frequency due to a shift in the energy levels of the OH molecule in a magnetic field, which changes along the filament.

Modern studies of solar radio emission are complicated by continuous power amplification and multifrequency external interference, which often completely overlap important frequency ranges. Many topical problems in solar radio astronomy require large effective areas of radio telescopes, high frequency and time resolutions, accurate spatial measurements, and a large dynamic range. It becomes relevant to change the concept of receiving recording equipment. This paper deals with topical problems of the physics of the solar corona in combination with optimal methods of observation with large instruments. The features and difficulties of combining high parameters—dynamic, spatial, temporal, and frequency resolutions—are considered. The proposed solutions of the new-generation observation complex implement the possibilities of intelligent selection of registration conditions in a multioctave mode with multichannel over 8000 channels/GHz with temporary permission up to 8 ms/spectrum. A multiobject observation mode becomes available from powerful flaring objects to faint structures of various nature. High-speed data processing makes it possible to implement an online mode of interference elimination, which is based on a fast statistical analysis of the spectrum with the selection of non-Gaussian (interference) structures. Methods for high-speed analysis of large-volume data (the principal component analysis method) and their presentation to the user are proposed. Examples of the operation of the complex in the range of 1–3 GHz are given. The prospects of a new approach for multiobject radio astronomy observations in the implementation of the RATAN-600 tracking mode are considered: from recombination lines to wide-range spectra, from low-contrast fluctuations to fast changes in flares, etc.

To implement the tracking modes of the RATAN-600 radio telescope, it is necessary to introduce new automation tools that provide a new quality of monitoring and control of the antenna system geometry [1, 2].In this work, the ACS is considered by the movement of the type 3 feed and the carriage, its structure is shown, new capabilities of the complex, previously unavailable on the RATAN-600 radio telescope, are considered.

We describe a new radio holography method of the RATAN-600 radio telescope antenna diagnosis and adjustment, using the radial movement of the reference panel. We present the results of geometric optical ray tracing of the "South + Flat" antenna system in the autocollimation mode and radio optical modeling of the hologram recording and field reconstruction procedure, taking noise into account. Estimates for necessary isolation and acceptable spatial separation between transmitting and receiving feeds, geometrical tolerances, and requirements to the reference panel motion control are discussed. The experimental results of the method application to the diagnosis of radial errors in the positioning of panels of the RATAN-600 main mirror are reported.

We describe two methods of fast condition diagnostics of the reflecting surface of the RATAN-600 radio telescope. The first one is based on a radio holography, and the second one relies on measurements of the random scattered background in the observations of the extended radio sources. Both methods were used in the antenna measurements, which proved the reflecting surface of the of the radio telescope main mirror to be in acceptable condition even after 20 years since the last resurfacing.