Kyushu University has initiated a project to understand the current micron-size debris environment by small satellites equipped with impact sensors. The objective of this study is to establish an estimation approach to identify an orbit on which a breakup event occurs using the measurement data from the satellites. This study assumes that two measurement satellites on different earth orbits get impacted with micron-size debris. In addition, this study is based on the presumption that the measurement satellite gets impact data at the line of node intersecting with the orbit of breakup object. This paper focuses on the Chinese anti-satellite missile test in 2007 and the US and Russian satellites accidental collision in 2009 to verify this estimation approach. In this study, a non-linear least squares method is used in order to estimate right ascension of the ascending node and inclination, which define an orbital plane. Using spherical trigonometry (a Napier's rule), an equation to estimate unknown obital elements is derived. Results from this study confirm that the proposed in-situ measurements technique can identify the orbital plane on which the above breakup events occurred.