## 2 Radiation in Space and Its Effects on Electronic Components
### Modeling Radiation Environments in Planetary Missions: Challenges and Approaches  
The space radiation environment around Earth is relatively well characterized, mainly due to the significant number of spacecraft orbiting Earth, which provide in situ measurements, specially in the LEO. However, radiation environments in inter-planetary missions, such as Solar Orbiter or the most recent Juice, can pose significant challenges for spacecraft and instrument design. Accurate radiation modeling is therefore critical for mission success. As an example, we compare in this section two different trapped particle models for the Jupiter environment and estimate solar cell degradation for the Juice mission.  
The two models used in this analysis are JOSE (Jovian Specification Environment) by ESA, and GIRE2 or DG2 (Divine and Garrett updated) by JPL. Five different Jupiter radial distances were considered in this comparison (5 Rj, 10 Rj, 15 Rj, 20 Rj, and 30 Rj). The MCSCREAM model was used to estimate solar cell power degradation (for AZUR 3G28) for the Juice mission, starting from the available differential fluxes at the five fixed distances and interpolating data.  
It can be seen in Table 1 that the differences between the two models can have significant impacts on solar cell performance and the estimated TNID (total non-ionizing dose). The use of the MCSCREAM model to estimate solar cell power degradation provides a valuable tool for mission designers to evaluate the expected performance of solar cells under different radiation conditions.  
Regarding the TID analysis, the general model used for ionizing dose is SHIELDOSE-2 RD, and an updated version called SHIELDOSE-2Q RD is used for the Juice mission due to its capability to treat higher-energy electrons. The method uses a precomputed dataset of doses from electrons, electron-induced Bremsstrahlung, and protons derived from Monte Carlo analysis. The dose is provided as a function of material shielding thickness. In Figure 1, the dose-depth curve is represented as a function of spherical aluminum shielding thickness, and it shows that the dose is dominated by trapped electrons, as well as that the contribution of trapped protons is insignificant compared to that of solar protons. The accumulated dose of solar energetic protons is shown in the figures with a 90% confidence level that higher doses will not be observed.  
As we can see in Figure 1, the expected TID for Juice goes above 1 Megarad for a typical wall thickness of 1.5 mm, considering a mission duration of approximately 12 years. In the case of the Solar Orbiter, the estimated TID for the total mission duration (7 years) is around 100 krad. As it will be discussed in the next section, the expected dose in an LEO mission such as the ISS corresponds to a total dose below 3 Gy/year in the worst case. This  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Cover Glass Thickness** & **150 \(\upmu\)m** & **300 \(\upmu\)m** \\ \hline JOSE (ESA) & 85\% & 90\% \\ GIRE2 (DG2-JPL) & 73\% & 82\% \\ \hline \hline \end{tabular}
\end{table}
Table 1: The preliminary estimation of solar cell degradation with the JPL updated model underlines the need of more effort in the solar cells’ design and in the Jupiter environment definition.  
is why COTS are gaining ground in the space sector, specially in LEOs. With time, it is likely that COTS may be used in interplanetary or Moon missions, since a 1 kGy (100 krad) TID is achievable with COTS technology.