RadioAstron: an interference response at the shortest wavelength

In conjunction with the early scientific program RadioAstron space radio telescope Spektr-R command Astro Space Center of Lebedev Physical Institute continued interferometric testing at the shortest wavelength radio telescope — 1.3 cm Finally, in May 2012 at this wavelength interference response was received from the compact quasar 2013 +370. The coherence time of the interferometer assessment showed a high level of stability of its space segment.

May 12, 2012, the trials in dual-frequency mode, the ground-space interferometer RadioAstron fixed interference response from a compact quasar 2013 +370 at a wavelength of 1.3 cm on the basis of "space radio telescope Spektr-R — 100-meter Effelsberg radio telescope (Germany) . " At the same time gave a positive correlation response at a wavelength of 6 cm between the Spektr-R radio telescope and Vesterborkskim WSRT (Netherlands). Delay values and frequency responses to interference between the wavelengths of 6 cm 1.3 cm, and consistent with each other.

The figures show the petals, obtained in the experiment on the left — Interference response from the quasar 2013 +370 at a wavelength of 6 cm, on the basis of "Spektr-R — Vesterborg" on the right — the interference response at a wavelength of 1.3 cm, based on the "spectrum P — Effelsberg. " On the vertical axis represents values correlated response radiation (in terms of signal / noise ratio) depending on the delay and the residual frequency interference.

    The projection of the interferometer base during these tests was a quarter the diameter of Earth.
    In its comments, the head of the Laboratory ASC FIAN, Doctor of Physical and Mathematical Sciences Yuri Kovalev explained: "The project RadioAstron extremely important to analyze the so-called coherence time. Coherence time of the call in radio interferometry maximum interval of time during which you can accumulate without loss of signal space radiation. Sensitivity of the experiment is greater the longer the coherent integration time, it is proportional to the square root of this value. On Earth, the coherence time at centimeter wavelengths is limited to the influence of the turbulent atmosphere, the ionosphere and the troposphere and has a value from 1 to 15 minutes. On the one hand, this parameter indicates how accessible radio astronomer studying faint objects, on the other hand, it reflects the overall stability of the entire complex, including the on-board atomic clocks. "
    For the analysis of the coherence time on two of the shortest wavelength interferometer observations were used March 15, 2012 at 6 cm and 12 May 2012 by 1.3 cm on the basis of "CRT-Effelsberg." The results are shown below in Figs.

The figures show the dependence of the signal / noise ratio of the storage time t. The figure on the left shows the dependence of the wavelength of 6 cm on the right — 1.3 cm for the straight line represents the expected dependence vt. (Approximation carried out directly on the chart excluding the last point — the wavelength of 6 cm — and the last three points — to 1.3 cm).

The signal / noise ratio, as the square root of the integration time (search interval lobe) increases substantially, up to 10 minutes, for a wavelength of 6 cm, — up to 2 minutes, — the wavelength of 1.3 cm     According to experts of ASC FIAN, the first assessment of the coherence time of the experiment demonstrates the highest level of stability of the space segment of the interferometer.
    / 14.06.2012 / According to the materials ANI "LPI-Inform"

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