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M. V. Sazhin V. E. Zharov T. A. Kalinina 《Monthly notices of the Royal Astronomical Society》2001,323(4):952-964
Parallax measurements allow distances to celestial objects to be determined. Together with measurements of their position on the celestial sphere, they give a full three-dimensional picture of the location of the objects relative to the observer. The distortion of the parallax value of a distant source affected by weak microlensing is considered. This means that the weak microlensing leads to distortion of the distance scale. The gravitational deflection causes a retrograde apparent motion of the image, which is revealed as a negative parallax. It is shown that the distortions may significantly change the parallax values when they amount to several microseconds of arc. In particular, at this level many measured values of parallaxes should be negative. 相似文献
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Astronomy Reports - It has recently become clear that the potential role of astrometry in cosmological studies has been underestimated. Some areas of cosmology that should be investigated using... 相似文献
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A general theory of terrestrial nutation is proposed assuming that the Earth is made up of four envelopes (atmosphere, mantle, fluid core, and solid core) and taking account of all important forces (viscous, electromagnetic, etc.). A theory for the effect produced on the Earth's nutation by viscous forces in the fluid core is developed based on experimental data on the viscosity of molten iron under pressure. The proposed theory predicts nutation in longitude and inclination with an rms deviation of 0.35 milliarcseconds. 相似文献
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Yu. N. Parijskij M. G. Mingaliev N. A. Nizhel’skii N. N. Bursov A. B. Berlin A. A. Grechkin V. I. Zharov G. V. Zhekanis E. K. Majorova T. A. Semenova V. A. Stolyarov P. G. Tsybulev D. V. Kratov R. Yu. Udovitskii V. B. Khaikin 《Astrophysical Bulletin》2011,66(4):424-435
The results of the first stage of the “Cosmological Gene” project of the Russian Academy of Sciences are reported. These results consist in the accumulation of multi-frequency data in 31 frequency channels in the wavelength interval 1–55 cm with maximum achievable statistical sensitivity limited by the noise of background radio sources at all wavelengths exceeding 1.38 cm. The survey region is determined by constraints 00 h < RA < 24 h and 40°30′ < DEC < 42°30′. The scientific goals of the project are refined in view of recent proposals to use cosmological background radiation data for the development of a unified physical theory. Experimental data obtained with the RATAN-600 radio telescope are used to refine the contribution of the main “screens” located between the observer and the formation epoch of cosmic background radiation (z = 1100). Experimental data for synchrotron radiation and free-free noise on scales that are of interest for the anisotropy of cosmic microwave background are reported as well as the contribution of these noise components in millimeter-wave experiments to be performed in the nearest years. The role of dipole radio emission of fullerene-type dust nanostructures is shown to be small. The most precise estimates of the role of background radio sources with inverted spectra are given and these sources are shown to create no serious interference in experiments. The average spectral indices of the weakest sources of the NVSS and FIRST catalogs are estimated. The “saturation” data for all wavelengths allowed a constraint to be imposed on the Sunyaev-Zeldovich noise (the SZ noise) at all wavelengths, and made it possible to obtain independent estimates of the average sky temperature from sources, substantially weaker than those listed in the NVSS catalog. These estimates are inconsistent with the existence of powerful extragalactic synchrotron background associated with radio sources. Appreciable “quadrupole” anisotropy in is detected in the distribution of the spectral index of the synchrotron radiation of the Galaxy, and this anisotropy should be taken into account when estimating the polarization of the cosmic microwave background on small l. All the results are compared to the results obtained by foreign researchers in recent years. 相似文献
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The commissioning of the RadioAstron space radio telescope observing in a radio-interferometer mode with baselines exceeding the baselines of ground-based VLBI systems by more than an order of magnitude requires revision of the formula used to calculate the delay of the arrival of the signal from a distant source to the telescopes in ground-based observations. This formula is derived taking into account all corrections necessary to achieve the required accuracy; numerical estimates of the contributions of all terms are presented. 相似文献
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Effects of instability of the Earth and celestial coordinate systems on Earth orientation parameters
Unknown secular and long-term changes in the Earth orientation parameters attributed to instability (possible rotation) of both the Earth and celestial coordinate systems (ECS and CCS) are studied. Rotation of the CCS due to changes in the coordinates of extragalactic sources resulting from gravitational lensing can lead to errors of the order of several microarcseconds in the orientation parameters. The rotation of the ECS due to the crust pressing on the mantle diminishes the tidal retardation of the Earth's rotation and produces long-term variations in the duration of the day (with a period of about 1500 years) and in the motion of the pole relative to the Earth's surface. 相似文献
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We review the methods of determining the alignment errors of the primary mirror and flat reflector elements of the RATAN-600 radio telescope using a modern coordinate measuring system based on the Leica absolute tracker AT402. We computed the kinematic corrections for the elevation drives. The accuracy of the measurement method was estimated. The antenna readout with the introduced kinematic corrections was tested. 相似文献
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The six-hourly values of the atmospheric angular momentum (AAM) functions computed by the U.S. National Meteorological Center (NMC) were used to estimate the effects of the atmospheric tides on the Earth's rotation. Variations of the equatorial components
1 and
2 of the AAM have periods close to gravitational tidesP
1 andK
1.The amplitudes of the detected variations in
1 and
2 functions have been found to be much larger than the theoretical ones, the reason of this amplification remains unexplained. According to theoretical formulations, these waves can be expressed only as retrograde motions. Because of frame effects, there is a correspondance between diurnal retrograde polar motion and precession-nutations and the atmospheric effect on polar motion cannot be detected from observations.The second part of this paper deals the effects of atmospheric tides in Earth rotation. High-frequency UT1 variations have been derived from VLBI and GPS techniques during the SEARCH'92 campaign (Study ofEarth-AtmosphereRapidCHanges) (Dickey et al. 1994). They have been compared to values derived by Ray et al. (1994) from global ocean tide model. The results obtained in the present paper show the existence of variations of thermal origin with an amplitude of about 1µs in Universal Time UT1. The agreement between observed and theoretical values is better when the determined thermal atmospheric tides are taken into account.Oceanic tidal signal explains a large part (60% of the signal variance) of the diurnal and sub-diurnal variations. Our results show that only a small part of the residuals (5%) accounts for the atmospheric tidal effects. The residual signal remains unexplained; it might be due to mismodelization of oceanic or atmospheric tides or effect of other geophysical phenomena. 相似文献
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Milyukov V. K. Burdanov A. V. Zhamkov A. S. Zharov V. E. Ivlev O. A. Nesterin I. M. Sysoev V. K. 《Solar System Research》2020,54(7):610-620
Solar System Research - Abstract—The paper analyzes the Russian scientific and technological capabilities to manufacture a space-borne observation platform for high-precision monitoring of... 相似文献