A.+F.+Zakharov

It is well-known that gravitational lensing is a powerful tool to investigate matter distributions including DM. Typical angular distances between images and typical time scales depend on gravitational lens masses. For microlensing case angular distances between images or typical astrometric shifts due to microlensing are about 10-5-10-6. Such an angular resolution will be reached with the space space—ground interferometer Radioastron. The basic targets for microlensing searches should be bright point-like radio sources at cosmological distances. In this case, an analysis of their variability and a solid determination of microlensing could lead to an estimation of their cosmological mass density, moreover, in this case one could not exclude a possibility that non-baryonic dark matter also form microlenses if the corresponding optical depth will be high enough. To search for microlensing the most perspective objects are gravitational lensed systems as usually, like CLASS gravitational lens B1600+434, for instance. However, for direct resolving these images and direct detection of apparent motion of the knots, a Radioastron sensitivity have to be improved, since an estimated flux density is too low and to observe the phenomena one should improve sensitivity in 10 times at 6~cm wavelength, for instance, otherwise, it is necessary to increase an integration time (assuming that a radio source has a typical core – jet structure and microlensing phenomenon is caused superluminal apparent motion of knots). In the case of a confirmation (or a disproval) of claims about microlensing in gravitational lens systems one can speculate about a microlens contribution into the gravitational lens mass. Astrometric microlensing due Galactic MACHOs actions is not very important because of low optical depths and long typical time scales. Therefore, a launch of space interferometer Radioastron will give new excellent facilities to investigate microlensing in radio band, since in this case there is a possibility not only to resolve microimages but also observe astrometric microlensing. We discuss also a possibility to evaluate paramameters of supermassive black holes to analyzing shapes and sizes of shadows around them.
 * Astrometry and astrophysics with the space telescope RADIOASTRON **
 * Alexander F. Zakharov, Institute of Theoretical and Experimental Physics,Moscow, Russia **