Abstract:With the increasing number of in-orbit micro-satellites and space debris, in order to ensure the safe operation of satellites, it is necessary to carry out effective tracking, detection and stable cataloging of micro-targets. Rader is the main equipment of near-earth space targets surveillance, and at the level of centimeter target detection and tracking, its working frequency is a key factor. The higher frequency is propitious to detect small targets and the more stable RCS will be obtained, but the equipment is more difficult to be implemented. In order to be suitable for practical engineering application, it is necessary to optimize the frequency based on the cost-effectiveness ratio. In this paper, from the view of target RCS, an optimal selection criterion of space targets monitoring signal frequency is proposed, and the value range of long wavelength ratio(ka) of this criterion is given. In order to explain the application of the optimal selection criterion more clearly, the signal frequency of targets with diameter of 5 cm and 10 cm under the criterion is given.