A Brief History of Radio Astronomy in the USSR by unknow

Author:unknow
Language: eng
Format: epub
Publisher: Springer Netherlands, Dordrecht

3.6 Radio Astronomy at GAISH in the Post-transition Period

Radio astronomy research at GAISH developed in the following directions during the 1970s: surveys of the sky on the RATAN-600 telescope, spectral studies, studies of kilometre-wavelength cosmic radio emission using instruments on board spacecraft, submillimetre astronomy and theoretical studies.

Sky Surveys on the RATAN-600

In accordance with the ideas behind its design and realised by its construction, this radio telescope is excellently suited for all-sky surveys. The knife antenna beam makes it possible to carry out comparatively rapid surveys of an appreciable area of the celestial sphere at centimetre wavelengths with high angular resolution in one coordinate. Another important feature is the ability to conduct observations simultaneously at several frequencies. This makes it possible to obtain instantaneous radio spectra during a survey. In contrast to earlier surveys, a multi-frequency survey on the RATAN-600 at 2, 3.5, 7.6 and 18 cm is being planned. Several receiver complexes operating at these wavelengths are being constructed in the RATAN-600 laboratory (partially on its own, partially in collaboration with other organisations). This work was done under the supervision of V. R. Amirkhanyan. The main wavelength of the survey is 7.6 cm.

Large databases require fully automated observation and data-processing procedures. With this idea in mind, a digital and computational complex was developed at GAISH under the supervision of M. G. Larionov. The main principles behind the mathematical reduction algorithms were due to A. G. Gorshkov, and work on the mathematical side of the complex was carried out under his supervision.

The survey observations were begun in 1978. The survey was carried out on the Southern sector of the RATAN-600 using two radiometers at 2 and 3.5 cm. A radiometer operating at 7.6 cm was added in 1979.

A survey of a section of the sky at declinations 0–7.5∘ was conducted in 1981, with the participation of Amirkhanyan, Gorshkov, A. A. Kapustkin, V. K. Konnikova, A. N. Lazutkin, Larionov, A. S. Nikanorov, V. N. Sidorenkov, L. S. Ugol’kova and O. N. Khromov. Of 650 sources detected in a 0.17-steradian area of the sky, 370 proved to be new objects that had never been mapped before; in other words, the number of new sources detected in the survey exceeded the number of previously known sources. This fully confirmed preliminary estimates made by Kardashev in 1964, who argued for the importance of carrying out surveys at centimetre wavelengths. This was the first survey in the Soviet Union that yielded a large number of new radio sources (apart from the Khar’kov survey, conducted at decametre wavelengths).

Analysis of the instantaneous spectra of the radio sources found in this survey showed that the mean spectral index at 2–3.5 cm was 0.4±0.4, roughly the same as had been obtained for non-instantaneous spectra at centimetre wavelengths. This was a very important result, since it indicated that the spectral characteristics of variable radio sources could be studied using non-simultaneous observations at different wavelengths.

The distribution of the 7.6-cm survey sources was found to be uniform on the sky. The survey data

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