ИСТИНА

After a brief review of the current relativistic gravitational experiments in the world we concentrate our attention on the two special researches are carried out in Russia at present. These are the experiment with original gravitational detector OGRAN in BNO INR RAS and Gravitational Red Shift experiment with Radioastron satellite. a) OGRAN experiment [1]. The opto-acoustical gravitational detector that structurally combines the principles of interferometrical and solid-state gravitational antennas is described. A large acoustical resonator, which is matched to a commensurate Fabry–Perot (FP) optical interferometer, serves as the sensitive element for recording changes in the gravitational-field gradient. In a test experiment, the spectral density of recorded spatial deformations (metric variations) was 10^{-19} Hz^{–1/2} at a frequency of 1.3 kHz within a band of ~4 Hz, which can be extended by an order of magnitude upon a corresponding increase in the sharpness of the interferometer mirrors. The new antenna is designed for detecting relativistic catastrophes (collapses) in the Galaxy and the nearest vicinity during complex (multi-channel) monitoring with neutrino telescopes of the Baksan Neutrino Observatory of the Institute for Nuclear Research, Russian Academy of Sciences. b) Red Shift experiment [2]. A unique test of general relativity is possible with the space radio telescope RadioAstron. The ultra stable on-board hydrogen maser frequency standard and the highly eccentric orbit make RadioAstron an ideal instrument for probing the gravitational redshift ect. Large gravitational potential variation, occurring on the time scale of ~24 hr, causes large variation of the on-board H-maser clock rate, which can be detected via comparison with frequency standards installed at various ground radio astronomical observatories. The experiment requires specific on-board hardware operating modes and support from ground radio telescopes capable of tracking the spacecraft continuously and equipped with 8.4 or 15 GHz receivers. Our preliminary estimates show that ~ 30 hr of the space radio telescope's observational time are required to reach ~ 2 10^{-5} accuracy in the test, which would constitute a factor of 10 improvement over the well known result achieved with GP-A mission.. At the final remarks we very briefly discuss nearest future projects for a study on non Newtonian gravity effects in the Solar system. References [1] S. N. Bagaev, L. B. Bezrukov, N. L. Kvashnin, V. A. Krysanov, S. I. Oreshkin, A. M. Motylev, S. M. Popov, V. N.Rudenko, A. A. Samoilenko, M. N. Skvortsov, and I. S. Yudin «A high frequency resonance gravity gradiometer» Review of Scientific Instruments 85, 065114 (2014); doi: 10.1063/1.4883901 [2] A. V. Biriukov, V. L. Kauts, V.V.Kulagin, D.A.Litvinov, V. N. Rudenko Gravitational Redshift Test with the Space Radio Telescope “RadioAstron” Astronomy Reports. Vol. 58, No. 11, pp. 783–795, 2014, c_ Pleiades Publishing, Ltd., ISSN 1063-7729,