# HERMES CubeSat Payload Thermal Balance Test and Comparison with Finite Volume Thermal Model
## 4 Test Results
It is possible to observe how tc1 gradient is always below 1 \({}^{\circ}\)C min\({}^{-1}\) as imposed by the test procedures to minimize thermo-mechanical stresses in the detectors. Furthermore, the maximum time needed to reach steady-state is registered by tc1 confirming the assumption made in Section 3.3. Figure 14: Temperature differences caused by heaters. Inside the pale red bands heaters are on. Figure 13: Heated internal boards temperatures and power. Inside the pale red bands heaters are on. The gradient analysis is also helpful to analyze the failure behaviour of tc12 compared to its redundant sensor tc17 (Figure 16). The TVAC temperature oscillations caused by the control action are not sudden due to the large mass of the baseplate, thus they do not justify the gradient spikes of tc12. Finally, the gradient analysis is also useful for Fault Detection Identification and Recovery (FDIR) either on board the CubeSat or by telemetry analysis on ground. Data can be exploited as footprint to spot TC failures on those components that have no redundancy on sensors for the temperature monitoring. Plus, the failure of tc12 confirms the necessity of such redundancy whenever monitoring a boundary condition during the TBT. As explained in Section 3.2, a failed acquisition of the temperature BCs would lead to a wrong model of the test environment, jeopardizing the thermal model correlation. In conclusion, auto-correlation matrices including all TCs have been computed for time intervals in which the temperature at the interface between payload and TVAC has been changed, that is whenever a new set point has been asked to the controller. Auto-correlation was performed by computing the Pearson's coefficient between each measure point and all others for a time interval of 6 h starting whenever a new set point is targeted by the TVAC controller. The goal was to observe the degree of correlation between each TC  
Figure 15: Payload internal components temperature gradients. Inside the pale red bands heaters are on. and the others to obtain a qualitative feeling about how temperature changes occurring in one measure point affect the other parts of the system, with a particular focus on how temperature changes at the DM interface with the TVAC affect the internal components of the payload. The DM TVAC interface is representative of the SM interface in the actual 3U CubeSat. Thus, by observing that region, it is possible to observe whether SM temperature variations will affect the temperature of the payload components. Auto-correlation matrices for internal and structural components are reported in Figure 17, and discussed in the following section. A numerical overview of the test is given in Table 5: the table summarises all steady-state temperature values according to the three different set points with heaters both on and off. The value reported in each table cell refers to the mean over the last hour before the heaters are switched on and before they are switched off so the two steady-states at each set point before and after switching on the heaters are shown.