Image Cross Correlation as a Measurement of Shape Model Quality

Introduction: Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer will use Stereophotoclinometry [1] (SPC) to generate the shape model of its target, Bennu. This shape model will be used to aid navigation and science processing [2]. The Altimetry Working Group has conducted numerous tests to evaluate the accuracy and performance of SPC in preparation for mission operations when OSIRIS-REx arrives at Bennu. The testing used several truth models that simulated both substantially rough and less rough shape objects with surface albedo, and also included navigational errors to identify SPC's robustness to meet the OSIRIS-REx accuracy requirements [3]. The main metric for the quality of a shape model is to subtract the generated model from the truth model (from which the simulated images were generated), and calculate the root mean squared differences of every vertex (RMS). Subtracting two models is the main tool that is typically used to evaluate two different shape models, such as what was done for Vesta [4]. For a global model, especially one built with direct measurement such as a laser altimeter, it provides a strong measurement of the model.