The Russian Academy of Sciences and Federal Space Agency, together with the participation of many international organizations, worked toward the launch of the RadioAstron orbiting space observatory with its onboard 10-m reflector radio telescope from the Baikonur cosmodrome on July 18, 2011. Together with some of the largest ground-based radio telescopes and a set of stations for tracking, collecting, and reducing the data obtained, this space radio telescope forms a multi-antenna groundspace radio interferometer with extremely long baselines, making it possible for the first time to study various objects in the Universe with angular resolutions a million times better than is possible with the human eye. The project is targeted at systematic studies of compact radio-emitting sources and their dynamics. Objects to be studied include supermassive black holes, accretion disks, and relativistic jets in active galactic nuclei, stellar-mass black holes, neutron stars and hypothetical quark stars, regions of formation of stars and planetary systems in our and other galaxies, interplanetary and interstellar plasma, and the gravitational field of the Earth. The results of ground-based and inflight tests of the space radio telescope carried out in both autonomous and ground-space interferometric regimes are reported. The derived characteristics are in agreement with the main requirements of the project. The astrophysical science program has begun.

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We carried out the first satellite experiment for searching the anisotropies of the microwave background. The main goal of the experiment was to obtain a radio brightness map of the sky at 8 mm. We obtained the direction and amplitude of the dipole component at 90% confidence level The variance analysis gives the most stringent constraints on fluctuations of the relic background. For the model with the Zeldovich spectrum of primordial fluctuations we found an upper limit on the quadrupole as 1.6×10−5 at 95% level. We are first to obtain model-independent estimates of the first 15 multipole components. We obtained upper limits on correlation function of angular fluctuations 〈ΔT1ΔT2〉 = 0.005 mK2 for the angular range from 20° to 160°. Intense galactic emission was observed over longitude interval from 90° to 270° and latitudes ±5°. The total flux from this longitude interval is approximately 56,000 Jy. The experiment studies confirmed that a space experiment gives a possibility to reach sensitivities high enough to estimate an anisotropy that is less than the values predicted by modern cosmological models.