Optimizing ExoMars Rover Remote Sensing Multispectral Science II: Choosing and Using Multispectral Filters for Dynamic Planetary Surface Exploration With Linear Discriminant Analysis

In this paper we address two problems associated with data‐limited dynamic spacecraft exploration: data‐prioritization for transmission, and data‐reduction for interpretation, in the context of ESA ExoMars rover multispectral imaging. We present and explore a strategy for selecting and combining subsets of spectral channels captured from the ExoMars Panoramic Camera, and attempt to seek hematite against a background of phyllosilicates and basalts as a test case scenario, anticipated from orbital studies of the rover landing site. We compute all available dimension reductions on the material reflectance spectra afforded by 4 spectral parameter types, and consider all possible paired combinations of these. We then find the optimal linear combination of each pair whilst evaluating the resultant target‐vs.‐background separation in terms of the Fisher Ratio and classification accuracy, using Linear Discriminant Analysis. We find ∼50,000 spectral parameter combinations with a classification accuracy >95% that use 6‐or‐less filters, and that the highest accuracy score is 99.6% using 6 filters, but that an accuracy of >99% can still be achieved with 2 filters. We find that when the more computationally efficient Fisher Ratio is used to rank the combinations, the highest accuracy is 99.1% using 4 filters, and 95.1% when limited to 2 filters. These findings are applicable to the task of time‐constrained planning of multispectral observations, and to the evaluation and cross‐comparison of multispectral imaging systems at specific material discrimination tasks. Plain Language Summary Specially designed cameras used by Mars rovers can see not just with the red, green and blue colors of trichromatic vision, but through a dozen or so distinct color channels, some of which extend into the near‐infrared. This super‐human color vision allows for the distinction of a greater diversity of materials, such as types of rocks and soils, than 3‐color vision. This extra color information requires extra data, but there is a limit to the data than can be transmitted from Mars back to Earth each day. If only some of these colors can be transmitted, then which should be chosen? And once transmitted, how should these channels be combined and contrast‐stretched to best convey the content of the scene? That is the problem we address in this paper. We have used mathematical methods from linear algebra to efficiently trial >200,000 possible combinations and contrast stretches of the 12 avai