The paper considers the concept of space radar monitoring complex performing Earth observation by two spacecrafts according to the technology of synthesized aperture in an interferometry scheme that allows obtaining a global high-precision digital model of the Earth’s relief. The first key problem when creating the complex is the development of an algorithm for determining the heights of the resulting image relative to the relativity surface. Unlike the traditional interferometer scheme using angular coordinates, radar gives the current coordinates of all points involved in the measurement scheme. This allows new algorithm using the difference between two space phase measurements of the downrange to the same surface element to be proposed. Both measurements are performed from two points of common position, spaced apart and representing the interferometry base. As a result, a simple estimate of the potential accuracy of altitude measurement and conditions of its implementation required for the structural scheme of space interferometry are obtained. The second key problem is the arranging coordinated kinematics of the flight of two spacecrafts, forming the base of the space interferometer with the orientation and dimensions that provide the necessary accuracy of altitude measurement. It is shown that both problems are systemically interrelated and the selection of principal solutions to optimize the complex as a whole requires simultaneous consideration and interdisciplinary coordination of the requirements determined by the specifics of each of the two problems. The technique for preliminary project evaluation of results obtained from the orbital group, visually representing all the relationships between individual characteristics of key problem areas of the complex and output target indicators of its work is proposed. The characteristics of the passive flight of spacecraft pair and the conditions for the obtaining high-quality interferometer measurement are considered. It is shown that these conditions are ensured only for a certain part of the orbit, resulting in decreasing efficiency of using the orbital group flight time, and the global survey of the planet relief takes about a year. In this context the possibility of using a small radial thrust applied for a long enough time exceeding a day is shown. As a result, the measurement conditions are stabilized, and the duration of the global survey of the planet relief is reduced to a few months. In addition, the efficiency of using the flight time of the orbital group increases, which allows performing Earth sounding using other possible programs.