The original preset schedule of space telescopes can be disrupted when they receive ultra-high-priority unpredictable tasks.The main objective of this study is to observe such unpredictable tasks,the instability of which leads to failures in delivering the promises made.This paper proposes a method for retaining the robustness of the original plan.We use space-based multi-band variable objects monitor (SVOM) mission as an example to introduce the proposed method.First,the reasons for instability are discussed in detail.Two proactive strategies are proposed to promote the robustness of the schedule.The proactive strategies use the available windows of a given list of jobs.However,the realistic problem of SVOM is analysed using a rescheduling algorithm based on NSGA-Ⅱ experiments with SVOM scenarios showing that the two proposed strategies are effective in reducing the instability caused by unpredictable interruption.