## 1 Introduction  
A photoelectric device will be subjected to a variety of challenging space radiation environments, including exposure to the inner and outer Van Allen radiation belts surrounding the Earth, as well as solar and galactic cosmic rays, plasma radiation, ultraviolet radiation, and other forms of radiation [1, 2]. The South Atlantic Anomaly (SAA), located at a longitude 90\({}^{\circ}\) W to 20\({}^{\circ}\) E and latitude 0\({}^{\circ}\) S to 40\({}^{\circ}\) S, is the region where the inner radiation belt is closest to the Earth's surface [3, 4]. This area, which covers a large part of South America and the South Atlantic, has an unusually high density of charged particles, primarily consisting of high-energy protons and electrons. When charged particles interact with photoelectric devices or materials, various radiation effects arise, such as total ionizing dose (TID), single event effect (SEE), displacement damage dose effect (DDDD), and charge effect on the material surface [5, 6]. The DDD effect is a critical concern for semiconductor photodetectors, as it shortens the lifetime of minority carriers through the interaction of radiation particles with lattice atoms in photoelectric materials. In contrast, photon-counting detectors based on MCP are less susceptible to the DDD effect [7, 8]. Soft errors, such as single event upset (SEU), or hard errors, such as single event latch-up (SEL) or single event burnout (SEB), are caused by highly energetic particles and lead to SEEs. Microprocessors and memory devices are highly vulnerable to SEEs, while photon-counting imaging detectors and analog circuit elements are relatively insensitive to SEEs. [9]. Therefore, TID is the primary concern for photodetectors and certain integrated circuits in this work. It is essential to implement protective measures that mitigate the damage and failure rates caused by space radiation, based on the mission requirements of space instruments and the specific characteristics of the orbit environment. The most commonly used radiation particle models in aerospace engineering, such as AP-8/AE-8 [10], only provide information about the omnidirectional flux of particles and lack directional information about particle incidence. However, space environment monitors on satellites such as FY-3A and FY-3B have been able to obtain high-energy electron and proton spectra and directivity data [11; 12]. By using the equipment's normal direction and the satellite's attitude, it is possible to calculate the angular distributions of ejected particles. The results indicate that directional flux is related to the coverage of the ejection angle and that spatial radiation dose has significant anisotropy. In addition, high-intensity particle radiation also exhibits an extremely strong directional distribution. The design of instrument structure and thermal analysis typically focuses on achieving a lightweight design [13; 14]. Even if radiation resistance is assessed, it is typically only carried out for single-layer and composite materials, and all-directional protection is not considered [15; 16; 17]. Our team has developed two scientific instruments, the Extreme Ultraviolet Camera [18; 19] and the Wide-angle Aurora Imager [20; 21], that were launched into orbit in 2013 and 2017, respectively, using photon-counting imaging detectors. In addition, our recently developed solar X-ray and Extreme Ultraviolet Imager [22], which began operations at the end of 2021, also uses photodetectors, such as a CCD and a four-quadrant photodiode. During the operation of the aforementioned instruments, short-term and long-term effects of the different types of detectors have been observed, especially the interference of charged particles on photon-counting imaging detectors. Due to satellite space constraints, it is difficult to completely avoid the direction of strong radiation in the instrument's installation position, the lens pointing, and the placement of signal processing circuits.