Correlation of a thermal model using infra-red camera data for thermo-elastic predictions
The representation of the temperature gradients across a spacecraft structure with a thermal model is key to have a good predictability of any thermo-elastic deformations. This is often not the objective of thermal models built for typical thermal control applications. Typically, it is sufficient to achieve the correlation criteria only at reference points and interfaces. This paper highlights the benefits of exploiting thermocouple data with infra-red camera images to improve the correlation of temperature gradients for a spacecraft structure. The study made use of data acquired from a thermo-elastic demonstrator test. The main objective was to develop techniques to give better predictions of thermo-elastic phenomena. The test structure was brought to steady state conditions in vacuum for a number of thermal load cases. The measured temperatures showed significant deviations from the initial predictions performed in a �classical� manner. Detailed features were introduced to the thermal model, which are often simplified for thermal control applications. In particular: accurate modelling of the heater lines, modelling edges of honeycomb panels to capture important gradients, refining the radiating areas and adding detail near mechanical interfaces. Image processing techniques were developed for the infra-red camera data allowing direct comparisons to the nodes of the thermal model. It was observed that correlating the model only at the discrete thermocouple locations was not sufficient to represent the spatial temperature gradients. Finally, the study demonstrated the added benefit of maintaining a parametric thermal model with individually modelled sensor and heater lines, to allow refinements of the underlying panel mesh. This study was performed at ESTEC, ESA in the framework of the I-METER R&D activity, implemented by Thales Alenia Space.