Abstract. The article describes microwave observations of the Sun with the radio telescope RT-32 of the Ventspils International Radio Astronomy Center. The observations were performed using a multichannel spectral polarimeter for the 6.3-9.4 GHz frequency range. A set of 2D microwave emission maps of the Sun for the Stokes I and V parameters has been obtained and analyzed.

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The generalized maximum entropy method (GMEM) is proven to recover both positive and negative local microwave sources on the 2.7 cm maps of the Sun taken with the radiotelescope RT-32 of the Ventspils International Radio Astronomy Center (VIRAC). The maps of the Sun need to be recovered due to high intensity of the side lobes of the RT-32 diagram pattern − up to 30% at 2.7 cm. The presence of negative local sources associated with Hα filaments is inferred from the 2.7 cm maps of the Sun (RT-32) compared with the 1.76 cm maps of the Sun (Nobeyama Radio Heliograph).

On the base of the 17 GHz radio maps of the Sun taken with the Nobeyama Radio Heliograph we estimate plasma parameters in the specific region of the sunspot atmosphere in the active region AR 11312. This region of the sunspot atmosphere is characterized by the depletion in coronal emission (soft X-ray and EUV lines) and the reduced absorption in the a chromospheric line (He I 1.083 μm). In the ordinary normal mode of 17 GHz emission the corresponding dark patch has the largest visibility near the central solar meridian. We infer that the reduced coronal plasma density of about ~ 5 × 10

An international VLBI experiment on radio location of the asteroid 2012 DA14 was organized on 2013 February 15–16, during its flyby close to Earth. The purpose of observations was to investigate and specify orbital parameters of the asteroid, as well as to evaluate its rotation period and other characteristics. The irradiation of the asteroid was performed by the RT-70 transmitter at Evpatoria (Crimea, Ukraine), while the reflected signals were successfully accepted by the two 32 m radio telescopes at Medicina (Bologna, Italy) and Irbene (Ventspils, Latvia). Processing and interpretation of the data were performed both in the Radiophysical Research Institute at Nizhny Novgorod and in the Ventspils International Radio Astronomy Center. The first results of this experiment are presented and discussed.