Vlbi research in the ”Radioastron” project: structure of the H2O maser in NGC 2071 IRS 1

Within the Radioastron interferometer scientific program, observational data of the H2O maser at a frequency of 22.2280 GHz in the NGC 2071 nebula were processed. A space radio telescope (SRT — 10 m) and three radio telescopes of the ground network: RT — 32 m (Medicina, Italy), RT — 32 m (Torun, Poland) and RT —64 m (Kalyazin, RF) took part in the observations. A map of the maser spot distribution has been obtained, where there are 13 spatial components with VLSR in the range 4.7 — 20.5 km/s. Correlation is observed on ground-space baselines for the component on VLSR = 14.3 km/s. Based on the visibility function dependence analysis from the baseline projection values, there was proposed a twocomponent model of this component spatial structure with the dimensions of the extended and compact constituent of 4 and 0.06 msec, i.e. 1.56 and 0.023 au, respectively.

Lineviewer — program of the astro space locator (asl) package for constructing and processing averaged spectra

LineViewer program operation a description and demonstration is presented. It is focused on the galactic and extragalactic masers primary spectra processing and visualization of observational data obtained with the SRT-10 space radio telescope (the “Radioastron” project). LineViewer is written in C ++ and is intended for correcting the signal bandwidth, constructing and analyzing the maser sources spectra averaged over time and fringe rate, and identifying maser spectral lines. The LineViewer software allows to analyze quickly the intermediate result and adjust it to obtain the relevant parameters for improving or detecting the correlation in spectral lines.

Probing the ionosphere by the pulsar B0950+08 with help of RadioAstron ground-space baselines

ABSTRACT The ionospheric scattering of pulses emitted by PSR B0950+08 is measured using the 10-mRadioAstron Space Radio Telescope, the 300-m Arecibo Radio Telescope, and the 14 x 25-m Westerbork Synthesis Radio Telescope (WSRT) at a frequency band between 316 and 332 MHz. We analyse this phenomenon based on a simulated model of the phase difference obtained between antennas that are widely separated by nearly 25 Earth diameters. We present a technique for processing and analysing the ionospheric total electron content (TEC) at the ground stations of the ground-space interferometer. This technique allows us to derive almost synchronous half-hour structures of the TEC in the ionosphere at an intercontinental distance between the Arecibo and WSRT stations. We find that the amplitude values of the detected structures are approximately twice as large as the values for the TEC derived in the international reference ionosphere (IRI) project. Furthermore, the values of the TEC outside these structures are almost the same as the corresponding values found by the IRI. According to a preliminary analysis, the detected structures were observed during a geomagnetic storm with a minimum Dst index of ∼75 nT generated by interplanetary disturbances, and may be due to the influence of interplanetary and magnetospheric phenomena on ionospheric disturbances. We show that the Space Very Long Baseline Interferometry provides us with new opportunities to study the TEC, and we demonstrate the capabilities of this instrument to research the ionosphere.

Design and implementation of large space radio telescope antenna

The design of large high-precision antenna is one of the key factors restricting the application and development of antenna. This paper presents a design method for high precision large-scale umbrella-shaped antenna. Studies have been performed on the configuration, cable net forming, mesh optimization, error analysis and rib design to achieve the high precision design. Then, a high-precision umbrella antenna prototype is designed and manufactured based on this method. Finally, the test results of the prototype proved the correctness and feasibility of the proposed method.

Effelsberg Monitoring of a Sample of RadioAstron Blazars

The launch of the RadioAstron space radio telescope provides a unique opportunity to study the extreme high brightness temperature of Active Galactic Nuclei (AGNs) with unprecedented long baselines of up to 28 Earth diameters. A coordinated ground-based flux density monitoring of RadioAstron targets is essential to determine the effect of interstellar scintillation (ISS) on the Space Very Long Baseline Interferometry (SVLBI) visibilities. Moreover, a combination/comparison of scintillation with SVLBI observations is expected to reveal the relative influence of source brightness temperature, compactness, and properties of the interstellar medium on the observed variability at centimeter wavelengths. In 2014 we started a RadioAstron target triggered flux monitoring with the Effelsberg 100-m radio telescope in support of this SVLBI mission. A total of 112 targets were observed during the five-session monitoring performed so far. In this paper we present a statistical study on the short-term flux density variability of the sample, which is focused on the variability characteristics and derived physical properties of the observed sources.

Software Correlator for Radioastron Mission

In this paper, we discuss the characteristics and operation of Astro Space Center (ASC) software FX correlator that is an important component of space–ground interferometer for Radioastron project. This project performs joint observations of compact radio sources using 10[Formula: see text]m space radio telescope (SRT) together with ground radio telescopes at 92, 18, 6 and 1.3 cm wavelengths. In this paper, we describe the main features of space–ground VLBI data processing of Radioastron project using ASC correlator. Quality of implemented fringe search procedure provides positive results without significant losses in correlated amplitude. ASC Correlator has a computational power close to real time operation. The correlator has a number of processing modes: “Continuum”, “Spectral Line”, “Pulsars”, “Giant Pulses”,“Coherent”. Special attention is paid to peculiarities of Radioastron space–ground VLBI data processing. The algorithms of time delay and delay rate calculation are also discussed, which is a matter of principle for data correlation of space–ground interferometers. During five years of Radioastron SRT successful operation, ASC correlator showed high potential of satisfying steady growing needs of current and future ground and space VLBI science. Results of ASC software correlator operation are demonstrated.