Microwave remote sensing from space provides a possibility of measuring some parameters important for understanding the environment of the Earth on the global scale such as sea surface temperature, ocean salinity, soil moisture, and sea ice concentration. However, realizing the full potential of passive microwave remote sensing from space requires putting relatively large antennas in space. Antenna size is the factor limiting the implementation of L-band radiometers in space to measure soil moisture, and it is also an important factor limiting the development of a microwave sensor to fill the gaps created by clouds in present-day visible and infrared sounding of the atmosphere. A possible means of overcoming this size limitation is to use aperture synthesis. This is a technique in which correlation receivers are used to coherently measure the product of the signal from pairs of small antennas with many different antenna spacings during a relatively large time of receiving radiation from pixel of surface by antennas. One can obtain very high resolution maps of a source by taking measurements with relatively small antennas with different baselines. The purpose of this paper is to develop an algorithm for radiometric signal processing and expressions for the map resolution and sensitivity