Spectra of Standard Radio Sources at the Current Epoch

The results of observations aimed at determining the spectra of standard radio sources in an “artificial-Moon” absolute flux scale at epoch 2015.5 at wavelengths of 3.5–18 cm are presented. The sample includes sources with small angular sizes, used as flux-density standards for the calibration of various types of antennas, including large synthesized apertures, over a wide range of frequencies. The artificial-Moon flux scale is constructed in a way that makes it the most accurate of existing scales, and the only scale for which source spectra are not deformed. The methods used to construct the articial-Moon flux scale are briefly described. Repeat measurements of the spectra of standard sources, required to preserve the accuracy of the flux scale, were carried out in 2014–2017 (at a mean epoch of 2015.5) on the 32-m telescope of the Svetloe Observatory of the Institute of Applied Astronomy at four wavelengths: 18, 13, 6.2, and 3.5 cm. The characteristic properties of the measurement methods are discussed, and the data obtained are compared with data from earlier epochs.