Shadow Chaser: a SmallSat Mission Concept to Measure the Upper Atmosphere of Uranus from Earth Orbit, and Enabling Aerocapture Orbit Insertion Benefits for Uranus Orbiter and Probe

We present the latest design of the Shadow Chaser mission concept that will measure the upper atmosphere of Uranus from Earth orbit using the stellar occultation technique. Upcoming stellar occultations by Uranus represent valuable opportunities to prepare for a potential aerocapture orbit insertion to be incorporated in the Uranus Orbiter and Probe (UOP) Flagship mission, the highest-priority new mission recommended by the 2022 Planetary Science Decadal Survey. An aerocapture maneuver enables faster interplanetary trajectories that do not depend on Jupiter gravity assist, and offer annual launch windows for UOP. However, an aerocapture maneuver’s precision depends on a-priori knowledge of the upper atmosphere, which today primarily comes from the highly uncertain Voyager 2 stellar occultations recently shown to be inconsistent with ground-based occultation measurements during the same era.

To improve upper atmospheric characterization, the Shadow Chaser will observe the occultations by Uranus on February 15, 2031, October 9, 2031 and February 6, 2032 from Earth orbit. Together with the occultation on April 8, 2025 (which we are planning to observe from the ground), these events represent the best opportunities to characterize the Uranian upper atmosphere before UOP arrival. We present the Shadow Chaser’s latest spacecraft and measurement design. We will also present results of analyses funded by NASA Space Technology Mission Directorate to establish the viability of aerocapture for UOP, quantify the benefits of reducing Uranian upper atmospheric uncertainties to improve the aerocapture design, and demonstrate that anticipated new stellar occultation data can be incorporated into the engineering design of aerocapture.