Planning and Execution of Juno’s Radio Occultation Campaign

Abstract

The latter part of Juno’s extended mission from 2023-2025 provides numerous opportunities to conduct radio occultation experiments of Jupiter’s atmosphere and ionosphere. Juno’s radio science instrumentation, consisting of dual X-band (8.4 GHz) and Ka-band (32 GHz) radio links to NASA’s Deep Space Network (DSN), was designed for precise measurements of Jupiter’s gravity field at a range-rate precision of <10 um/s. This work describes the preparation campaign undertaken to adapt the existing instrumentation and spacecraft design to make precise radio occultation measurements of Jupiter’s atmosphere and ionosphere. Due to lack of onboard stable frequency reference, the spacecraft will conduct these occultations in a coherent mode, where the downlink signal is coherent with the uplink from the DSN. Although the spacecraft cannot perform a maneuver to counteract the refractive bending, small bias attitudes will be implemented to increase the depth of the occultation measurements. These two constraints required significant preparation work to ensure successful data collection. These occultations will result in atmospheric temperature-pressure profiles down to 500 mbar and ionospheric electron density profiles across a wide range of latitudes, including in the polar and auroral regions of the gas giant.