Computed tomographic imaging spectroscopy for the measurement of re-entry break-up and demise

Computed tomographic imaging spectroscopy for the measurement of re-entry break-up and demise

Spectral measurements of re-entry events are essential to the development and validation of the numerical models of re-entry that are required for safe and sustainable space industries. Imaging spectrometers are the dominant instrument for re-entry capsule measurements; and, while they have had some success in re-entry demise observations, they cannot discriminate between multiple objects with overlapping spectral signatures. These successes have required substantial separation of the objects along the dispersion-normal axis. To overcome this restrictive requirement, spectral imaging methods that are suitable for measurements of objects with overlapping spectral signatures are required. In this work, the viability of the computed tomographic imaging spectroscopy (CTIS) technique for re-entry applications is demonstrated. A prototype CTIS instrument was developed and used to measure scenes replicating aspects of the spatial and spectral properties of re-entry break-up fields; a spatiospectral field significantly different to those previously investigated using CTIS. A new CTIS calibration method which is suitable for in-situ fieldwork calibration was developed. The prototype instrument was able to reconstruct both the high-frequency spatial features and the narrowband spectral features of the test scene, demonstrating its potential for material identification during re-entry. Through measurements of a known-radiance source, CTIS was shown to be capable of resolving spectral irradiance in wavelength and amplitude, should the spectral sensitivity of the instrument be suitable. These newly validated capabilities of CTIS could enable its application in broader contexts, such as the high-enthalpy flows produced in shock tunnels and plasma facilities. Practical recommendations to develop the prototype into an observation-ready instrument design are provided.