N. A. Dugin

First Results of the VLBI Experiment on Radar Location of the Asteroid 2012 DA14

Abstract 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.

Technique and Instrumentation for Precision Measurements of the Intensities of Extraterrestrial Radio Sources

We consider methods for decreasing the measurement error of the intensities of radio sources. The design of a two-temperature standard of noise radiation for calibrating antennas in the case of absolute measurements of the radiation flux densities of radio sources by the method of a “black” disk is described. We consider a method for taking into account the nonuniformity of the intensity distribution around the studied cosmic source, which facilitates choosing reference regions.

Radio interferometric observations of solar bursts in the decimeter range with millisecond temporal resolution

We describe the radio interferometric equipment for observation of solar spike-like events at decimeter wavelengths with millisecond time resolution. The equipment was tested using a two-element interferometer (2 RT7, f=540 MHz, baseline 416 m) at the “Staraya Pustyn” radioastronomical station (RAS) of the Radiophysical Research Institute of Nizhny Novgorod (NIRFI) in October–November 1993 and in September–October 1994. Over 20 solar bursts of different durations, which showed considerable interference response, were detected with time resolution 0.256 ms. The typical time variation scale of the bursts was from 50 to 200 ms. Bursts with time scales less than 20 ms were absent. The actual possibility of measuring the displacements of radio source brightness centers with accuracy up to 1–2 arc s is shown.

Measurements of Interferometer Parameters at Reception of GLONASS and GPS Signals

Abstract The present paper deals with the calibration method of interferometers with antennas having a small effective area, on the quasinoise signals of GLONASS and GPS navigation satellites. Algorithms for calculation of antenna coordinates and instrumental delay from the analysis of correlation interferometer response to signals of satellites in the near field of the instrument were reviewed. The method was tested in VLBI experiments on interferometers with medium and large baselines that included radio telescopes of NIRFI and VIRAC. The values of the antenna coordinates and instrumental delay with an error within the limits of one discrete were obtained. The sources of measurement errors and ways to improve the accuracy of results were analysed.

Radio Interferometric Research of Ionosphere by Signals of Space Satellites

Abstract Since 2012, the Radiophysical Research Institute and the Lobachevsky State University at Nizhny Novgorod, Russia and the Ventspils International Radio Astronomy Centre at Irbene, Latvia are making radio interferometric experiments on study of ionosphere parameters in a quiet (natural) state of medium and research of artificial turbulence of the ionosphere, heated by the emission from the SURA facility. Remote diagnostics of the ionosphere is implemented using a method of radio sounding by signals of navigation satellites in combination with the Very Long Baseline Interferometry (VLBI) method. As a result of spectral and correlation analysis, interferometric responses of the two-element (RRI–UNN) and three-element (RRI–UNN–Irbene) interferometers were received by observations of 12 satellites of the navigation systems GLONASS and GPS. Here the first results are reported.

AN EXPERIMENT ON RADIO LOCATION OF OBJECTS IN THE NEAR-EARTH SPACE WITH VLBI IN 2012

Abstract An experiment on radar location of space debris objects using of the method of VLBI was carried out in April, 2012. The radar VLBI experiment consisted in irradiation of some space debris objects (4 rocket stages and 5 inactive satellites) with a signal of the transmitter with RT-70 in Evpatoria, Ukraine. Reflected signals were received by a complex of radio telescopes in the VLBI mode. The following VLBI stations took part in the observations: Ventspils (RT-32), Urumqi (RT-25), Medicina (RT-32) and Simeiz (RT-22). The experiment included measurements of the Doppler frequency shift and the delay for orbit refining, and measurements of the rotation period and sizes of objects by the amplitudes of output interferometer signals. The cross-correlation of VLBI-data is performed at a correlator NIRFI-4 of Radiophysical Research Institute (Nizhny Novgorod). Preliminary data processing resulted in the series of Doppler frequency shifts, which comprised the information on radial velocities of the objects. Some results of the experiment are presented.

Possibility of Fast Determination of Radio-Interferometer Parameters

We propose a method for fast determination and systematic monitoring of certain radio-interferometer parameters (the baseline projection and the mounting-site longitude). The method is based on reception of the emission from point radio sources at certain values of their hour angles with the subsequent processing of measurement results using a developed algorithm. We show that the method is applicable for determining the parameters of radio interferometers with both two- and one-channel receivers.