1,2,1,2,3,4,5,1,2,1,2,1,2,1,2,4,5,4,- 1Department of Industrial Engineering, University of Bologna, Forlì, Italy
- 2Centro Interdipartimentale di Ricerca Industriale Aerospaziale, University of Bologna, Forlì, Italy
- 3Boston University, Boston, MA, USA
- 4Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- 5Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot, Israel
- 6Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA
- 7School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA, USA
- 8Southwest Research Institute, San Antonio, TX, USA
The Juno spacecraft, currently in orbit around Jupiter, provides a unique opportunity to investigate the planet’s atmospheric and ionospheric structure through radio occultation experiments. This study presents an analysis of radio signals transmitted between Juno and Earth-based antennas as the spacecraft passes behind Jupiter’s limb, offering vertical profiles of electron density in the ionosphere with unprecedented resolution.
A radio occultation experiment utilizes the precise tracking of a spacecraft’s radio signal as it is occulted by a planetary body from the line of sight of a ground-based antenna. As the signal propagates through the planetary atmosphere, it experiences bending and phase delay due to refractive index gradients. The passage of the radio signal through Jupiter’s ionosphere induces a frequency-dependent Doppler shift, superimposed on the non-dispersive contributions from the neutral atmosphere and spacecraft dynamics.
Juno's radio science subsystem employs a dual-frequency link, involving coherent X-band (8.4 GHz) and Ka-band (32 GHz) signals transmitted to Earth. By exploiting a linear combination of the sky frequencies recorded at the ground antenna in the two bands, it is possible to isolate the downlink dispersive effect, which is proportional to the integrated electron content along the ray path. This enables the retrieval of accurate vertical electron density profiles through an inversion process based on a ray-tracing technique, assuming Jupiter’s ionosphere to be oblate and axially symmetric. Additionally, an uncertainty quantification has been carried out through a Monte Carlo simulation, providing confidence intervals for each altitude level above Jupiter’s 1 bar reference ellipsoid.
Within the Juno extended mission, starting from July 2023 radio occultations of Jupiter have been occurring at a cadence of approximately one per month, near perijove. In this context, we report on a series of occultation events spanning multiple perijoves, with particular attention to the most recent experiments that probed high latitudes near the auroral zone close to Jupiter’s north pole. Understanding auroral effects is essential for characterizing the coupling between Jupiter’s magnetosphere and ionosphere, and for evaluating their broader impact on the dynamics and thermal structure of the planet’s upper atmosphere.
Our findings contribute to the growing understanding of Jupiter’s upper atmosphere, demonstrating the unique capabilities of dual-frequency radio occultations and paving the way for future ionospheric studies in support of upcoming exploration missions such as JUICE and Europa Clipper.
How to cite: Caruso, A., Gomez Casajus, L., Coffin, D., Buccino, D., Smirnova, M., Galanti, E., Gramigna, E., Parisi, M., Togni, A., Zannoni, M., Tortora, P., Park, R. S., Kaspi, Y., Withers, P., Hubbard, W., Orton, G., Steffes, P., and Bolton, S.: Characterization of Jupiter’s Ionosphere using Juno’s Radio Occultation Measurements, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–12 Sep 2025, EPSC-DPS2025-621, https://doi.org/10.5194/epsc-dps2025-621, 2025.
