Spectral Spatial Fluctuations (SSF) of the Cosmic Microwave Background Radiation (CMBR) temperature are considered as a result of an interaction of primordial atoms and molecules with CMBR in proto-objects moving with peculiar velocities relative to the CMBR. Expected optimistic values of ∆T /T are 2×10 −5 −2×10 −6 for SSF caused by HeH + at z =20-30 which are possible redshifts of early reionization scenario. The bandwidth of the lines is 0.1-2% depending on the scale of protoobjects and redshifts. For the SSF search CMBR maps in different spectral channels are to be observed and then processed by the Difference method. Simulation of the experiment is made for MSRT (Tuorla Observatory, Finland) equipped with a 7 × 4 beam cryo-microbolometer array with a chopping flat and frequency multiplexer providing up to 7 spectral channels in each beam (88-100 GHz). Expected ∆T/T limit in the experiment is 2×10 −5 with 6 ′ -7 ′ angular and 2% frequency resolution. Simulation shows that SSF may be recognized in the angular power spectrum when S/N in single frequency CMBR maps is as small as 1.17 or even something less for white noise. Such an experiment gives us a possibility to set upper limit of SSF in MM band and prepare future SSF observations.
International audienceThe results of geometrical optics modelling and optimization of the modified optical system of RATAN-600 radiotelescope are given. Suggested modifications to the optical system include the introduction of an auxiliary mirror in order to increase focal length, reduce aberrations, and expand the field of view. In this context, diffraction modelling is necessary to determine the beam pattern shape and study the polarization characteristics of the antenna. We used the aperture integration method along with the ray tracing for the calculation of the antenna beam patterns in co- and cross-polarization. Finally, the multilevel fast physical optics (PO) method was adapted for near field and beam pattern simulation of RATAN-600 radio telescope to avoid the GO approximation of the aperture field and take the finite wavelength effects into accoun
The paper presents the results of analysis of astroclimatic conditions in the Big Telescope Alt-azimuthal (BTA) region (40°N–50°N; 35°E–55°E). Using data from the European center for medium-range weather forecast ReAnalysis (ERA-5), we estimated the averaged spatial distributions in total cloud cover, vertical integral of mean kinetic energy, vertical component of wind speed, and wind speed shears, as well as inverse values of Richardson number 1/Ri. An extensive region with the development of atmospheric flows is formed south and southeast of BTA in winter. High inverse values of the Richardson number, spatial heterogeneities in vertical wind speed, and significant wind speed shears in the lower atmosphere are observed in this region. In terms of turbulence development over BTA, the best time for astronomical observations falls in summer, when vertical shears of wind speed are weakened in the lower atmospheric layers. The situation is opposite in the upper troposphere. In winter, BTA is in the region of moderate vertical wind shears. In summer, a region with increased vertical wind speed shears is formed. Taking into account that the intensity of optical turbulence decreases rapidly with height, better image quality can be expected in summer. Such structure of the atmosphere does not allow one to directly apply atmospheric models in order to describe turbulence based on the turbulence strength as function of its ground values, or to use the classical model describing the turbulence velocity as function of air flow velocity at the height corresponding to the 200 hPa level.
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