ИСТИНА

The development of space technologies opens new perspectives in solving the fundamental problems of gravity. We propose the experimental investigation of General Relativity (GR) in space experiments in following: a) measurement of post-Newtonian parameters (PPN), b) gravity wave detection in the low frequency band. The accuracy, with which GR is currently confirmed, is fractions of percent: 2.3× 10(-5) . However, in spite of the remarkable success of GR in the weak-field approximation, there are many reasons to consider alternative relativistic theories of gravity that predict the existence of effects other than GR, thus motivating new fundamental gravitational experiments. In this connection, the experimental measurements of PPN of parameters play a special role. To improve the accuracy of measurement of geodetic effects in the gravitational field of the Earth the clusters of spacecrafts, connected by microwave radio links and optical links, are widely used. Such a scheme allows to suppress effectively a coherent noise acting on the spacecraft, and to measure the distance between the satellites within a fraction of a millimeter. This technology was already tested for GRACE and GRAIL NASA missions. Furthermore, there are technologies allowing to effectively compensate non-gravitational noise to the level of 10(-10) - 10(-12) \ m/s(2/sqrt{Hz}) . The project, which assume the lunch of cluster of the spacecrafts intended to study fundamental processes in the Universe, including the measurement of the PPN parameters and low frequency gravitational waves, is proposed in this report. We study the space-based systems in a configuration of few spacecrafts on different orbits in the gravitational field of the Earth for measuring these effects. Measurements of distances between spacecrafts are performed using microwave radio links, laser interferometry and ultra stable frequency standards. Developed modern technologies for distant measurements allow to reach the accuracy of few nm during integration time of 1 s. Respectively, in some hours of measurements it is possible to reach the accuracy of 0.1 nm or even better. Such an accuracy of measurement of the intersatellite distance is able to provide determination of one of the post-Newtonian parameter (gamma) with an accuracy of 2× 10(-9) .