Highly Sensitive Receiving Complex Designed for Ground VLBI Observations at Wavelengths of 92,18, 6, and 1.35 cm

The development of very long baseline radio-interferometry methods (VLBI) allowed us to increase the angular resolution of radio astronomy tools from several degrees to thousandth fractions of arc second, i.e., by more than six orders of magnitude. Such a high angular resolution makes it possible to obtain images of celestial objects with the finest structure, which provides basically novel possibilities in the area of astrophysics and astronomy. This method is a single tool for studying the structure of quasars, radio-galaxies at cosmological distances. In the framework of the Radioastron Project, we developed and tested a fourfrequency highly sensitive receiving complex for the wavelengths:  = 92 cm, 18 cm, 6 cm, and 1.35 cm. The complex was designed for the equipment of ground receiving stations participating in VLBI interferometric observations. An RT-22 radio telescope is equipped with this receiving complex at the Pushchino Radio Astronomy Observatory. A VLBI station for four wavelengths was organized on the basis of this instrument. The general flowchart of the receiving complex for VLBI observations on an RT-22 in Pushchino is presented in Fig. 1.