## 4 Conclusions  
This work studied the viability of using a payload camera breadboard to detect space debris in LEO orbits. The breadboard was built with COTS components, choosing Aptina MT9J001 as the image sensor, Arducam as the image controller, and a Fujian lens. The camera was characterised to predict the limiting magnitude. The theoretical results demonstrated an optimistic magnitude value of 10.2 for an integration time of 1 s and 11.4 for an integration time of 3 s for a point-like source. Nonetheless, for streak-creating trailing objects, like space debris in orbit, longer exposures do not result in higher counts over the same pixels but in longer streaks. If stationed on the ground, for circular orbits at an altitude of 800 km, resulting in average sky motions of about 706 arcsec/s, our sensor is able to detect debris with a diameter of 0.88 m (if viewed at a pessimistic phase angle of 120 deg) and with a diameter of 0.30 m (if viewed at an optimistic phase angle of 20 deg). If placed in orbit, where the link between sky trailing rates and orbital distances is much more complex, our sensor would be able to detect almost co-orbiting debris of the under \begin{table}
\begin{tabular}{l c c c c} \hline \hline  & \multicolumn{4}{c}{**Observation Parameters**} \\ \hline Starlink & 1346 & 3601 & 2602 & 1349 \\ \hline Date & \multicolumn{4}{c}{27 July 2022} \\ \hline Time (UTC) & 22:44:43 & 22:47:15 & 22:54:56 & 22:56:35 \\ \hline Exposure time & \multicolumn{4}{c}{3} \\ (s) & 548.28 & 543.37 & 550.55 & 549.1 \\ \hline Azimuth (deg) & 169.97 & 310.17 & 72.70 & 208.63 \\ \hline Elevation (deg) & 50.99 & 38.12 & 34.24 & 46.16 \\ \hline Range (km) & 689.40 & 830.13 & 906.12 & 735.25 \\ \hline Sun azimuth (deg) & 329.87 & 330.48 & 332.33 & 332.74 \\ \hline Sun elevation (deg) & \(-\)25.13 & \(-\)25.37 & \(-\)26.07 & \(-\)26.22 \\ \hline Solar phase angle (deg) & 30.10 & 113.72 & 67.61 & 48.16 \\ \hline Estimated magnitude & 5.1 \(\pm\) 0.2 & 6.5 \(\pm\) 0.2 & 7.1 \(\pm\) 0.2 & 6.4 \(\pm\) 0.2 \\ \hline Estimated diameter (cm) & 91 \(\pm\) 16 & 158 \(\pm\) 28 & 63 \(\pm\) 11 & 60 \(\pm\) 11 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Observation details and size estimation. cataloged size-scale of 10 cm from 110 km to 320 km distance from it, depending greatly on the Sun-debris-sensor phase angle. Satellites and rocket bodies were observed, from the ground, to test the camera detectability and validate the theoretical simulations, reaching good results and, hence, showing the viability of our breadboard for space surveillance. Author Contributions: J.F. : methodology, software, investigation, data curation, writing original draft preparation, visualisation; P.G. : conceptualisation, methodology, validation, investigation, data curation, writing review and editing, supervision; N.P. : conceptualisation, methodology, validation, investigation, data curation, writing review and editing, supervision; R.M. : conceptualisation, methodology, validation, investigation, data curation, writing review and editing, supervision; R.G. : conceptualisation, methodology, validation, investigation, writing review and editing, supervision; All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. This research received funding in the framework of the project FLY.PT with references POCI-01-0247-FEDER-046079 and LISBOA-01-0247-FEDER-046079 and with the title Mobilizar a Industria Aeronautica Nacional para a Disrupcao no Transporte Aereo Urbano do Futuro (FLY.PT), co-funded for Fundo Europeu de Desenvolvimento Regional (FEDER) of European Union through the Programa Operacional Competitividade and Internacionalizacao (POCI) of the Programa Operacional Regional de Lisboa 2020, integrated into Portugal 2020. This work was supported by Fundacao para a Ciencia e a Tecnologia (FCT) through the research grants UIDB/04434/2020 and UIDP/04434/2020, CENTRA project UIDB/00099/2020; LAETA project UIDB/50022/2020. The authors declare no conflict of interest.