Pre-Computed Navigation and Backplanes in Support of Legacy Outer Planet Missions

Legacy missions such as Voyager, Galileo, Cassini, and New Horizons have provided a treasure trove of historic and irreplaceable data about the outer planets. Making these datasets available to future researchers in the most accessible and analysis-ready manner possible is important to preserving their value. Our project aims to make these datasets easier and more efficient to use by solving two tedious and time-consuming tasks that must be performed by most researchers: image navigation and geometric metadata generation.

A prerequisite for planetary image analysis is knowledge of what each image pixel represents. Typically, this is done using the SPICE toolkit along with a set of "kernel" files that define aspects of the planetary system and spacecraft geometry as a function of time. Unfortunately, spacecraft kernels as supplied by mission teams commonly have errors on the order of dozens to hundreds of pixels, making them of limited value. Researchers must fix these errors by performing their own image navigation using the SPICE toolkit and identifiable reference points such as stars, bodies, or ring features to determine accurate spacecraft pointing. After navigation is complete, the SPICE toolkit can be used to provide geometric information about each image pixel, such as lighting and observation geometry, to enable further scientific exploration.

While the SPICE toolkit has extraordinary capabilities, it also has a steep learning curve. We are eliminating the need for scientists to perform these steps themselves by 1) navigating each image with a precision approaching one image pixel and creating new SPICE kernels containing the improved pointing, 2) creating a collection of summary images, which provide visual context for each navigated image, and 3) creating a comprehensive set of backplanes that describe the geometric content of each pixel within each image. A backplane is an array with the same dimensions as the source image, containing a calculated quantity that is associated with each pixel's location. The backplanes we produce for each image include, for each body in the field of view, latitude, longitude, and surface resolution, and for the ring plane, radius, longitude, and resolution; we also include incidence, emission, and phase angles for both. These pre-computed backplanes can entirely eliminate the need for many scientists to learn the SPICE toolkit. All of our products will be archived with NASA's PDS.

Our navigation and backplane generation techniques [1,2] have already been proven in several research contexts, including Saturn's F Ring [3,4] and Titan's cloud layers [5]. Over the next two years, we would like to partner with additional researchers to help us beta test our results so that we can provide the greatest long-term benefit possible to the research community. If you are interested, please contact us.

[1] French et al. 2014, DPS 46, #422.01; [2] French et al. 2016, DPS 48, #121.14; [3] Lessard et al. 2022, DPS 54, #317.01; [4] French et al. 2024, DPS 56, #204.03; [5] Hanson et al. 2025, Geophys Res Lett, 52, e2024GL113415 (also abstract this conference).