A high dynamic range camera for Lunar polar science

Abstract:

Revelio is a high dynamic range, high sensitivity visible/near infrared (VNIR) camera that expands the range of imaging environments for landed or roving missions on the lunar surface. Shadowed regions appear in much greater contrast to sunlit regions on the lunar surface than on bodies with an atmosphere, an issue that is particularly problematic given that many of the highest priority lunar landing sites for science, exploration, and technology are in or near permanently shadowed regions. Revelio helps solve this problem by making it possible to acquire high-resolution, high-science-content images over a range of ambient illuminations – i.e., a high sensor dynamic range (>15,000). This range enables characterizing volatile deposits, identifying potential resources, measuring cratering rates, and carrying out other surface operations in scenes with shadowed regions without an artificial light source.

Revelio combines a flight heritage sensor with Ball’s automatic gain and exposure control (AGEC) and pixel merging algorithms. Revelio’s sensor sends out high- and low- gain images in parallel for every frame. This is supplemented by AGEC algorithms, extending the dynamic range achievable in a single image to maximize signal to noise ratios (SNRs) in direct sunlight and in shadow (intrascene dynamic range > 2x10⁸x). The electronics design enables a low power (~3.5 W without heating/cooling) compact camera. Revelio is a versatile camera that can be used for both science and surface operation applications. An implementation with a butcher block filter enables characterizing surface morphology for geologic context and measuring regolith composition and compactness/roughness. Additionally, the camera can be used panchromatically for surface operations. Revelio satisfies multiple objectives and goals from NASA’s Planetary Science Decadal Survey, Lunar Exploration Roadmap, and Lunar Human Exploration Strategic Knowledge Gaps (SKG) for polar missions where low solar elevation results in highly shadowed scenes.