For a transatmospheric spacecraft such as a reentry spacecraft controlled by the RCS (Reaction Control System), how to obtain the RCS control moment under the real flight condition is a difficult problem. In this paper, a technique of system identification1 is proposed to obtain the RCS control moment. The triangle-based equivalent RCS jet model is established and candidate aerodynamic model of reentry spacecraft aerodynamic parameters identification is selected. Then model structure is optimized by stepwise linear regression. The parameters identified via linear regression are then used as the initial values of maximum likelihood identification. The state space model considering the second-order term of gravity and the earth's rotation and ellipsoid model is obtained. A parameter identification algorithm based on maximum likelihood criterion and Newton-Raphson iterative algorithm is established. Colored noise assessment methods are used to evaluate the identification results. The identification results based on the reentry spacecraft's actual flight data verifies the effectiveness of the method established in this paper which serves to identify the aerodynamic and RCS moment simultaneously.
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