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The incessant overcrowding of the space around the Earth with new operative satellites is a critical issue in the Space Traffic Management (STM) framework, especially in last years with the beginning of the new space economy. The operative life of the active satellites is seriously endangered by the numerous uncontrolled objects, i.e., the space debris, which populate the outer space. The consequence of an impact between these objects may be catastrophic, as proved by the events in the recent past. In this context, the in-orbit explosions both of dismissed satellites and rockets stages are one of the main causes of space debris generation. For this reason, a suitable observation and detection strategy of the fragments generated by these events is necessary, e.g., by means of optical systems. In this work, the Sapienza Space Systems and Space Surveillance Laboratory (S5Lab) shows the results, by means of a graphical method, of the short-term analysis of the in-orbit explosions that involved the third stage of the Russian rocket FREGAT-SB and the fragmentation of the military Chinese satellite YUNHAI 1–02. In order to approach the study of a fragmentation event, an observation strategy and an analysis method have been developed. The research of fragments was focused on the orbital plane leading to estimation of fragments' number and their distribution. The measurements obtained through the images were analyzed in order to understand if the objects present in the images are either included in the North American Aerospace Defense Command (NORAD) catalogue or not. The unknowns could be fragments. The next analysis follows the hypothesis of the isotropic explosion confined only on the tangential impulses. In first approximation, only semi-major axis and eccentricity change due to the impulse. Therefore, it is possible to generate a new Two-Line Elements (TLE) for each fragment leading to an association between the impulses and the affected TLEs. A new, simple, and fast analysis method was developed, specifically to improve the impulse association. It consists in a graphical method where it is possible to see the distribution of the fragments with respect to the original body using the angular distance trend between them. [ABSTRACT FROM AUTHOR]

The number of satellites orbiting the Earth has significantly increased and large constellations based on thousands of satellites are currently being designed and operated. Among them the Starlink project, owned by SpaceX, is in advanced phase. The massive presence of orbiting objects could have a negative impact on astronomical research. In the case of observations with long exposure times and/or wide field of view (FoV), numerous bright tracklets, caused by the reflection of sunlight on a transiting satellite, may appear in the images. For this reason, the Sapienza Space Systems and Space Surveillance Laboratory (S5Lab), which has been involved in research on space debris and space surveillance for many years, started a new research project on the photometric characterization of some satellites of the Starlink project, using red, green and blue filters and comparing the results with observations performed without filters in order to analyze the features of the transit of Starlink satellites. The observations will stress the high complexity of the Starlink satellites reflection pattern, producing interesting results concerned with the used filters and the observation geometry. [ABSTRACT FROM AUTHOR]