Uranus Orbiter and Probe: A Novel Approach to Meet the Challenges

Abstract—Motivation: The Origins, Worlds, and Life Decadal Survey recommends a Uranus Orbiter and Probe (UOP) mission as the next planetary flagship [1]. The current President’s Budget Request for Fiscal Year 2025 does not support NASA-funded mission studies until 2027 [2], which will likely result in missing a potential Jupiter Gravity Assist (JGA). We thus need to find other trajectory options to Uranus, arriving ideally before Equinox in 2050 for unique observations. Additionally, other challenges drive the UOP design. We describe these challenges and a novel mission concept which mitigates them while achieving comparable science return to that in the Decadal Survey mission concept.Challenges: The UOP flagship faces numerous challenges. Losing the JGA means reducing flight system mass to maintain flight times to Uranus of 13.5 yrs with thermally-benign perihelia above 0.9 AU. Another challenge is power. Uranus will be 18–19 AU from the Sun, which makes Radioisotope Thermoelectric Generators (RTGs) the best power source option. Based on best estimates, the inventory of RTGs is likely to be limited in this timeframe, driving a desire to reduce power and number of RTGs required while maintaining flagship-worthy science and the earliest possible launch date that budget profiles will allow. Another challenge is ensuring launch date flexibility which allows CONOPS-similar backup launch opportunities. Perhaps the ultimate challenge is to meet these previously mentioned challenges using a credible low-cost and low-risk approach. Approach: Mass and power drivers were examined, informed by >50 years of experience in developing space science missions at JPL. In this preliminary study, we assumed the same Decadal UOP study payload and probe mass [3]. Significant power and mass reductions were achieved by techniques such as eliminating reaction wheels and adopting new electrical power distribution architectures. While some technology evolution was required, we took a “no miracles” approach. We chose a trajectory that allows launch any year without a JGA and without going much below 1 AU (no Venus flybys), thus providing yearly launch and backup opportunities with virtually identical CONOPs and environments.Results: By using a combination of new design approaches, we were able to match the same payload and science as the Decadal UOP study with 42% less dry mass and a requirement of only two Next Gen Mod 1 RTGs. The mass reduction enabled a trajectory that matches the Decadal UOP’s cruise duration while providing yearly launch opportunities. Our approach used a Falcon Heavy Expendable and a kick stage instead of a Falcon Heavy Expendable. The design was run through JPL’s Team X which demonstrated that all appropriate design and cost margins were achieved. Mission development and operations phase costs were comparable to the UOP Decadal study costs. This approach is potentially extensible to other missions.Conclusions: Based on this initial study, it appears that all challenges can be met with adequate margins while achieving comparable Decadal study science using this novel approach. Evolutionary technology was used which can achieve Technology Readiness Level (TRL) 6 by the end of Phase A.