Copyright © 2018 by the International Astronautical Federation (IAF). All rights reserved. This paper proposes to incorporate environmental change due to major breakups into estimation on orbital debris population through in-situ measurements. In-situ measurements should be conducted to understand the environment of sub-millimeter-size debris. Debris smaller than 2 mm cannot be detected by any ground-based observations even though such tiny debris may lead to a spacecraft's missions end. The IDEA project, which has been initiated at Kyushu University to detect sub-millimeter-size debris, aims to monitor the environment of sub-millimeter-size debris and the environmental change due to major breakups. The previous study proposed a statistical method to estimate the environment utilizing the in-situ measurement data. The evaluation in the previous study has demonstrated that the proposed method can estimate the orbital environment sufficiently. To incorporate environmental change due to major breakups into the proposed environmental estimation, this paper simulates the detection and the environmental estimation of sub-millimeter-size debris considering a major breakup. Firstly, the estimation by the proposed method utilizing impact data only from a breakup is demonstrated. This simulation demonstrates that the proposed method can estimate the environmental change due to the breakup when sufficient impact data is obtained. Secondly, a situation in which the impact data measured by the satellite includes both the debris from the breakup and the others is simulated. The result confirms that the orbital region in which the orbital environment is exacerbated by the breakup can be estimated even when the satellite detects the debris both from the breakup and other orbital regions. In conclusion, the estimation method of this study can identify the environmental change due to a major breakup utilizing in-situ measurement.