ИСТИНА

After a first registering of GW radiation from binary BH coalescence practically all non Newtonian effects predicted by GR have got its experimental confirmation. Further development of experimental gravitation is now associated with a more precise measurement of the same effects to check a border of GR validity and to search for a new physics. It is believed that such experiments must be carried in a deep underground or in the board of cosmic apparatus to depress influence of environmental noises. Common feature of the experiments consists in registration of space-time curvature variations produced by small changes of weak gravity fields. Hope of increasing accuracy of measurement at present is associated with the new instrumentation based on optical frequency standards and matter wave interferometers admitting the gain in three order of value of space -time intervals. In this talk we put attention on gravitational experiments are carried out at present in RAS: i) an original underground gravitational detector OGRAN [1] and ii) the gravitational red shift test with the Earth satellite [2]. In the final part we discuss briefly a new possibility of gravity gradient measurement using the new instrument - the atomic fountain gradiometer. i) The opto-acoustical gravitational setup OGRAN structurally combines the principles of interferometer and solid-state gravitational antennas. A large acoustical resonator matched to the commensurate Fabry–Perot (FP) optical cavity serve both as the sensitive elements for registering gravity gradient variations induced by GW. At room temperature the sensitivity of the setup is ~10^{-19} Hz^{–1/2} at a frequency of 1.3 kHz and it can be enhanced up to 10^{-21} Hz^{–1/2} with the cooling to nitrogen temperature. The new antenna is designed for detecting relativistic catastrophes (collapses) in the Galaxy and the nearest vicinity during joint (multi-channel) monitoring with neutrino telescopes of the Baksan Neutrino Observatory INR RAS/ ii) The unique test of general relativity is carried out by Astro Space Center of LPI RAS with the space cosmic apparatus RadioAstron. The ultra-stable on-board hydrogen maser and the highly eccentric orbit make RadioAstron an ideal instrument for probing the gravitational redshift effect. Gravitational potential variations, occurring on the orbiting time scale, causes large variations of the on-board H-maser clock rate, which can be detected via comparison with frequency standards installed at ground radio astronomical observatories. The experiment requires specific on-board hardware operating modes and support from ground radio telescopes capable of tracking the spacecraft with 8.4 or 15 GHz receivers. Estimates show that accumulation of data at 30 orbits allows 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