## 2 Materials and Methods
When a wireless communication system is applied to a satellite component as a small communication module, the radiation tolerances of the control IC and wireless module are important. Even if the radiation tolerance of the latter is high, its overall reliability will decrease if the radiation tolerance of the former is extremely low. Therefore, the radiation tolerance evaluation of both components is necessary, and a control-IC microcomputer with equivalent or higher radiation tolerance than that of the wireless module should be selected. Various radiation tolerance evaluations have been reported to date concerning consumer microcomputers for installation in small satellite applications, including the PIC16F877 [12], ATmega128 [12], MSP430 FR5739 [13], and H8-3048 [21] devices. Although the Greek team has also used a software configurable transceiver IC at almost the same time, the radiation tolerance results have not been reported. In this study, radiation tolerance evaluations were performed for both the CC1120 wireless module and the ATmega2560 microcontroller, which has an Arduino development environment and many control pins, and is highly versatile when mounted on a satellite. In this study, we conducted irradiation tests at the Tandem Accelerator Facility (Tokai Village, Naka District, Ibaraki Prefecture) of the Japan Atomic Energy Agency (JAEA). In the irradiation tests, an Au thin-film was used as the scattering film for the ion-beam irradiation  
Figure 4: Fabricated wireless communication system. part. Each test object was placed on the circumference for irradiation (Rutherford scattering) to enable the simultaneous acquisition of the test data for the small single-chip wireless communication module and microcomputer, and improve the test efficiency. Figure 5 shows a photograph of the Au scattering film used in the irradiation test. During the test, the package on top of the IC was removed to expose the Si substrate inside the IC. Through this decapping process, which was used in prior studies [20; 22], the effect of radiation attenuation by the IC package was eliminated (Figure 6). Figure 7 shows the schematic and photograph of the test setup. The wireless communication module installed within the chamber was set to transmit test data continuously in a constant transmission mode using the control Arduino installed outside the chamber. To confirm the communication operation, and determine the current and voltage variations during the irradiation test, a high-frequency cable and power cable were connected to an external power supply. An antenna and switch circuit were installed in the control room and implemented via a connector from inside the chamber. Equipment to receive the radio waves transmitted from the wireless module was installed in the control room, and the time history, transmission data, and received signal strength indicator (RSSI) at the time of reception were visually monitored and recorded at all times. Figure 8 shows communications operation and transmission data monitoring during the irradiation test in the control room. Figure 5: Au film for heavy ion-beam scattering. Figure 6: Wireless communication module with exposed IC internal board section. Figure 7: Schematic of the test equipment and its arrangement in the chamber. SEUs and SELs are the main effects of radiation exposure on semiconductor devices. Therefore, we obtained the tolerance data for these phenomena. Three types of ion beams (Ar, Kr, and Xe) were selected as the heavy-ion species for irradiation. Based on the irradiation tests performed by [PERSON] et al. [12; 13], evaluations were first performed for Xe, which has the highest probability of producing a single event, followed by those for the lower-energy Kr and Ar. The SEUs and SELs of the wireless communication module were measured at the linear energy transfer (LET) value, i.e., the radiation energy transfer rate of each irradiated ion species. The SEU and SEL tolerances with respect to the LET were evaluated.