# A Review of Requirements for Gamma Radiation Detection in Space Using CubeSats
## 6 Mechanical and Thermal Analysis  
In order to assess the payload resilience to mechanical strains and to predict its thermodynamic behavior, modal and thermal analysis are in general recommended. The goal of the modal analysis is to reveal possible resonant frequencies that could damage the payload during the launch phase.  
The goal of the thermal analysis is to assess the temperature variation of the satellite components along the orbit and to highlight possible overheated regions that could bring to an emergency shut down in order to mitigate the risk of failure.  
In this section, the modal and thermal analysis, both developed under Siemens NX Design software, is presented. As the simulation using finite element method is highly demanding in terms of computation, a simplified rendering of payload and the other subsystems is often required. In order to get meaningful insights from the simulation, material details along with physical properties must be preserved.  
Concerning the modal analysis, the payload has been fixed to eight anchor points and connected in pairs by means of threaded bars as visible in Figure 18.  
Figure 17: The event seen at the level of the readout electronics in 1 ms time window. The two channels on top (namely, CH1 and CH2) did not detect events, while the peaks visible in the CH3 and CH4 correspond to gamma-rays detected in a 175 \(\upmu\)s time range. The red star indicates the simultaneous detection of gamma-rays in both channels due to a Compton effect.  
The analysis generated the first ten natural frequency modes of the system: note that only the lowest frequency (1153 Hz) falls under 2000 Hz, which is the upper limit of the typical vibrational profile of the launching vehicle [34]. Requirements and limits for the vibrational characteristics of the payload depend on the launcher; however, the first natural mode should not appear below a few hundred Hz (typically \(<\) 200 Hz) and normal mode frequency should not shift more than 5% before and after vibrational tests [35].  
To provide a comprehensive thermodynamic analysis for the payload, the whole satellite should be taken into account in order to correctly model the heat exchange among subsystems. In the thermal simulation presented here, a simplified version of the LIGHT-1 satellite (see Section 2) has been considered.  
Figure 19 shows the temperature distribution on various subsystems of the satellite after completing the first orbit. The expected heat generation of each subsystem has been considered.  
Figure 19: The satellite thermal analysis results after one orbit. In this specific case, the deployables are facing the sun. Maximum temperature is \(\sim\)53 \({}^{\circ}\)C (red region) and minimum temperature is \(\sim\)0 \({}^{\circ}\)C (blue region). Courtesy of Basel AlTawil.  
Figure 18: The payload modal analysis. This simulation meshing is based on 3D CTETRA 10 mesh, with maximum mesh size of 5 mm and minimum of 1 mm. Courtesy of Basel AlTawil.  
In this specific case, the temperature span is within the typical temperature operative range (\(-20\ ^{\circ}\mathrm{C}\div 60\ ^{\circ}\mathrm{C}\)) of a CubeSat spacecraft and therefore no active cooling or heating system shall be required, leaving the overall mission power budget unaffected.