Damage detection and warning for space debris collision is one of the most serious problems for space systems operations. Estimation of impact force and its location is necessary for such systems, which can be realized by inverse analysis. However, this analysis requires an enormous amount of computation time, which may preclude on-board processing. To overcome this problem, this paper presents two improvement procedures based on an inverse analysis by using a priori knowledge on duration of impact force that is assumed much shorter than measurement time. Improvements are demonstrated in terms of calculation time and the effects of errors in coefficient matrix on estimation accuracy are analyzed based on the analytical solutions of the structure vibration model with acceleration data corrupted by white noise.