### Space-Based Space Surveillance (SBSS)
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**USA** & \multicolumn{2}{c}{**Russia**} & \multicolumn{2}{c}{**Japan**} & \multicolumn{2}{c}{**Europe**} \\ \hline
**System** & **Year** & **System** & **Year** & **System** & **Year** & **System** & **Year** \\ \hline \hline \multicolumn{1}{c}{Thule radar} & 1943 & Dnepr radar & 1963 & BSGC & 2002 & GRAVES (France) & 2005 \\ \hline \hline \multicolumn{1}{c}{Eglin radar} & 1969 & Dunay-3U radar & 1968 & KSGC & 2004 & TIRA (Germany) & 2009 \\ \hline \hline \multicolumn{1}{c}{GEODSS} & 1980 & Daryl radar & 1984 & & & \\ \hline \hline \multicolumn{1}{c}{SST} & 2011 & Don-2N radar & 1996 & & & \\ \hline \hline \multicolumn{1}{c}{Space fence} & 2020 & Okno optical complex & 1997 & & & \\ \hline \hline \multicolumn{1}{c}{} & \multicolumn{2}{c}{Krona system} & 2008 & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Main ground-based SSA systems. tracking for various commercial actors and orbital startup companies [18]. The overall business of SDA faces formidable challenges. Most objects are extremely difficult to observe when they pass between the Earth and the Sun. Although space-based sensors can provide observations much closer to the Sun, they have limitations when the target positioned between Sun and the sensor [19]. Recent technological advances have led to the concept of multiple spacecraft operating in optimal coordination to accomplish desired mission goals [20]. Considering this, distributed satellite systems (DSS) is a promising concept for the future of SSA and STM. DSS mission architectures move away from the monolith system concept to adopt multiple elements that interact, cooperate, and communicate with each other [21; 22; 23], resulting in new systematic properties and/or emerging functions. Different types of DSS have been proposed to date, including constellations [24], clusters, swarms, trains, fractionated spacecraft, and federated satellites [25; 26; 27; 28]. From the system architecture point of view, these concepts vary across different verticals, such as the number of assets, homogeneity of the assets, physical separation between the assets, and so forth [29]. For better understanding of various DSS configurations, the reader is referred to references [30; 31; 32; 33; 34; 35; 36]. In contrast to the conventional ground-based systems whose observations are conducted from accurately surveyed locations, SBSS platforms are subjected to positional errors and tracking errors caused by onboard TSPI/Navigation systems and tracking sensors, respectively. These errors can be represented geometrically in the form of ellipsoids which can be combined to form the total uncertainty volume that determines the total uncertainty in the tracking estimates [37] to support separation assurance (SA) and collision avoidance (CA) between the RSO, which is followed by the application of relevant collision avoidance manoeuvres. There exists a duality to the approach mentioned previously. On one hand, for the existing DSS constellation, optimized manoeuvres can be performed to avoid collisions with RSO. Alternatively, the design of the astrionics onboard could be optimized to mitigate errors and achieve mission objectives. In this paper, a non-cooperative SBSS scenario is analysed, in which DSS spacecraft collaboratively track the RSO subject  
Figure 2: Various SBSS missions during their respective timelines. to specific errors in tracking and navigation systems for positioning that will ultimately determine the uncertainty volume or a confidence region around the detected RSO.