Planning operations in Jupiter’s high-radiation environment: optimization strategies from Juno-ultraviolet spectrograph

The Juno Ultraviolet Spectrograph (Juno-UVS) is a remote-sensing science instrument onboard the Juno spacecraft that has been in polar orbit around Jupiter since July 2016. Juno-UVS measures photon events in the ultraviolet from 68 to 210 nm. It is primarily used to observe emission from the Jovian aurorae but is also sensitive to other sources, such as UV-bright stars, sky background Lyman-alpha emission, and reflected sunlight. However, Juno-UVS is also sensitive to the effects of penetrating high-energy radiation, which results in elevated count rates as measured by the instrument detector array. This radiation presents a challenge for efficiently planning the acquisition of mission science data, as data volume is a valuable (and finite) resource that can quickly be filled when the spacecraft periodically passes through regions of high radiation. This background radiation has been found to vary significantly on both short (spacecraft spin-modulated) timescales, as well as longer timescales from minutes to hours during each close approach to Jupiter. This variability has required a multipronged approach in the operation planning of hardware (such as, dynamic instrument voltage adjustment) as well as onboard software (such as, utilizing data quality factors for the selective storage of science data). We present an overview of these current mitigation/optimization techniques and planning strategies used for this instrument, which will likely also be useful for the development and operations of future instruments within high radiation space environments (e.g., the ESA JUICE mission or NASA’s Europa Clipper).