The space industry has experienced substantial growth in recent years, leading to rapid advancements in space exploration and space-based technologies. Consequently, the study of electronics and sensor performance in extreme environments has become crucial. Light sensors play a pivotal role among the detectors utilized in space-based missions. Nonetheless, the space environment poses several challenges for these systems. Among the emerging photodetectors, the single-photon avalanche diode (SPAD) has showcased exceptional timing performance, sensitivity to low light, and scalability due to its increasing compatibility with complementary metal–oxide–semiconductor technology. To investigate the feasibility of implementing SPADs in harsh environments and improving current systems, we first focused on studying the radiation hardness of SPADs. We subjected various SPAD systems to testing using protons and neutrons, which are sources of both ionizing and non-ionizing damage. The impact of radiation on all the figures of merit of SPADs under various operating conditions involving temperature and bias was characterized. Notably, the SPADs were exposed to the highest displacement damage dose (> 1 PeV/g) ever delivered. Furthermore, we explored methods to mitigate damage post-radiation exposure by incorporating annealing steps. Multiple applications using the developed megapixel SPAD camera and individual SPAD pixels were successfully demonstrated. The findings illustrate that a well-engineered SPAD camera is capable of high dynamic range 2D imaging, making it well-suited for space-based imaging scenarios with varying light contrast scenes. Our investigation also encompassed an exploration of how the design of SPAD-based systems and potential radiation-induced damage can influence imaging performance. We presented 3D multi-object ranging utilizing the SPAD camera. Furthermore, the camera's resolution facilitated the reconstruction of 4D light-in-flight imaging by harnessing the concept of apparent superluminal motion. Additionally, the thesis explores wide-field fluorescence lifetime imaging microscopy (FLIM) and spectral FLIM systems. These systems are integrated with machine learning algorithms for data processing, resulting in a significant reduction in processing time by over four orders of magnitude compared to conventional methods. Furthermore, we found that the sensitivity of SPADs to ionizing radiation and high avalanche gain makes them suitable for particle or radiation detection. A particle coincidence timing precision down to 15.3 ps was achieved, which is the best recorded to date. These applications possess potential for planetary exploration, astronomy, and material studies.