Dark Current Degradation in SiPMs Along Full Orbits in LEO

Utilizing the LabOSat-0l payload with a dedicated Daughter Board, we investigated the behavior of four ONSEMI MicroFC-60035-SMT Silicon Photomultipliers in DC mode in Low Earth Orbit from January 2020 to February 2023. During this time frame, an increase in the measured current of the Silicon Photomultipliers was noted, prompting the exploration of various hypotheses. Among these, there was the potential damage to either the Silicon Photomultipliers themselves or some of the associated electronics. Through a comprehensive examination of the Silicon Photo-multiplier behavior across complete satellite orbits, we were able to dismiss the theory of electronic damage. Our findings lead us to the conclusion that the observed increase in the measured SiPM current is a result of damage sustained by the Silicon Photomultipliers themselves, possibly incurred from interactions with highly energetic particles in orbit. Furthermore, our study demonstrates that the DCDC boost converter LT3571, respon-sible for biasing the Silicon Photomultiplier sensors, remains unaffected by temperature fluctuations in Low Earth Orbit, maintaining proper functionality throughout the mission's three-and-a-half-year duration.