  We consider the problem of rover relocalization in the context of the
notional Mars Sample Return campaign. In this campaign, a rover (R1) needs to
be capable of autonomously navigating and localizing itself within an area of
approximately 50 x 50 m using reference images collected years earlier by
another rover (R0). We propose a visual localizer that exhibits robustness to
the relatively barren terrain that we expect to find in relevant areas, and to
large lighting and viewpoint differences between R0 and R1. The localizer
synthesizes partial renderings of a mesh built from reference R0 images and
matches those to R1 images. We evaluate our method on a dataset totaling 2160
images covering the range of expected environmental conditions (terrain,
lighting, approach angle). Experimental results show the effectiveness of our
approach. This work informs the Mars Sample Return campaign on the choice of a
site where Perseverance (R0) will place a set of sample tubes for future
retrieval by another rover (R1).
