Juno
The JUNO mission
The mission, launched in August 2011, is aimed to improve our knowledge regarding the origin and evolution of Jupiter. Together with the scientific activity, Italy will provide JUNO with the Ka-band translator system (KaTS), the on-board instrument that will allow the acquisition of highly precise radiometric measurements, and that will play a key role in the JUNO radioscience experiment.
One of the main goals of the NASA Juno mission was the determination of the interior structure of the planet, which can be achieved by measuring its exterior gravitational field. Accurate gravity measurements are enabled via the radioscience instrumentation hosted onboard the spacecraft, i.e., the Ka-band Translator System (KaTS), funded by ASI. This instrument enables establishing a Ka/Ka-band radio link with a ground station (DSN’s DSS-25, in Goldstone, California). When used in conjunction with the Deep Space Transponder (DST), which establish a X/X radio link, the two radiometric data can be used to provide cancellation of plasma noise (mainly solar plasma and Io Plasma Torus) via a multi-frequency link calibration scheme, therefore providing extremely accurate Doppler data.
During gravity-dedicated passes, the spacecraft collected valuable data which determined for the first time the north-south asymmetric nature of Jupiter’s zonal gravity field (Iess, et al., 2018), which has been explained by zonal winds penetrating deep into the planet, down to about 3000 km (Kaspi, et al., 2018), while the interior rotates as a solid body (Guillot, et al., 2018). The analysis of more data collected up to the mid of Juno’s prime mission revealed the presence of unknown accelerations, at the level of 2x10-8 m/s2 acting on the spacecraft (Durante, et al., 2020).
Recent analysis based on a more comprehensive dataset explained the data with normal modes (Durante, et al., 2022) internal oscillations of the planet which perturb the density profile and thus its gravity field. Results show an amplitude spectrum with a peak radial velocity of 10–50 cm/s at 900–1200 μHz (compatible with ground-based observations) and provide an upper bound on lower frequency f-modes (with radial velocities smaller than 1 cm/s at the surface). These new Juno results could open the possibility of exploring the interior structure of the gas giants through measurements of the time-variable gravity or with onboard instrumentation devoted to the observation of normal modes, which could drive spacecraft operations of future missions.
In the extended mission, Juno is also targeting flybys of the Galilean moons to make new discoveries. Two recent flybys of Io provided an updated measurement of Io’s tidal deformation (Park, et al., 2025), which is consistent with Io having a mostly solid mantle and confirming that a shallow global magma ocean does not exist within the moon.
Scientific publications
Parisi, M., E. Galanti, S. Finocchiaro, L. Iess, and Y. Kaspi (2016). Probing the depth of Jupiter's Great Red Spot with the Juno gravity experiment. Icarus 267, 232–242. https://doi.org/10.1016/j.icarus.2015.12.011
Durante, D., T. Guillot, and L. Iess (2017). The effect of Jupiter oscillations on Juno gravity measurements, Icarus 282, 174–182, https://doi.org/10.1016/j.icarus.2016.09.040
Galanti, E., D. Durante, S. Finocchiaro, L. Iess, and Y. Kaspi (2017). Estimating Jupiter’s Gravity Field Using Juno Measurements, Trajectory Estimation Analysis, and a Flow Model Optimization, The Astronomical Journal 152:2. https://doi.org/10.3847/1538-3881/aa72db
Bolton, S. J., A. Adriani, V. Adumitroaie, M. Allison, J. Anderson, S. Atreya, et al. (2017). Jupiter’s interior and deep atmosphere: The initial pole-to-pole passes with the Juno spacecraft, Science 356, 821-825. https://doi.org/10.1126/science.aal2108
Folkner, W.M., L. Iess, J.D. Anderson, S.W. Asmar, D.R. Buccino, D. Durante, et al. (2017). Jupiter gravity field estimated from the first two Juno orbits, Geophysical Research Letters 44. https://doi.org/10.1002/2017GL073140
Iess, L., W.M. Folkner, D. Durante, M. Parisi, Y. Kaspi, E. Galanti, et al. (2018). Measurement of Jupiter’s asymmetric gravity field, Nature 555, 220-222. https://doi.org/10.1038/nature25776
Kaspi, Y., E. Galanti, W.B. Hubbard, D.J. Stevenson, L. Iess, T. Guillot, et al. (2018). The extension of Jupiter’s jet to a depth of thousands of kilometers, Nature 555, 223-226. https://doi.org/10.1038/nature25793
Guillot, T., Y. Miguel, B. Militzer, W.B. Hubbard, E. Galanti, Y. Kaspi, et al. (2018). A suppression of differential rotation in Jupiter’s deep interior, Nature 555, 227–230. https://doi.org/10.1038/nature25775
Galanti, E., Y. Kaspi, F. Simons, D. Durante, M. Parisi, and S.J. Bolton (2019). Determining the depth of Jupiter’s Great Red Spot: a Slepian approach, The Astrophysical Journal Letters 874, L24. https://doi.org/10.3847/2041-8213/ab1086
Notaro, V., D. Durante, and L. Iess (2019). On the determination of Jupiter’s satellite-dependent tides with Juno gravity data, Planetary and Space Science 175, 34–40. https://doi.org/10.1016/j.pss.2019.06.001
Durante, D. (2019). Effect of Juno’s solar panel bending on gravity measurements, Journal of Guidance, Control, and Dynamics 42:12, 2694–2699. https://doi.org/10.2514/1.G004503
Serra, D., G. Lari, G. Tommei, D. Durante, L. Gomez Casajus, V. Notaro, et al. (2019). A Solution of Jupiter's Gravitational Field from Juno Data with the ORBIT14 Software, Monthly Notices of the Royal Astronomical Society 490, 766–772. https://doi.org/10.1093/mnras/stz2657
Durante, D., M. Parisi, D. Serra, M. Zannoni, V. Notaro, P. Racioppa, et al. (2020). Jupiter’s gravity field halfway through the Juno mission. Geophysical Research Letters 47, 4. https://doi.org/10.1029/2019GL086572
Notaro, V., D. Durante, L. Iess, and S. Bolton (2021). Determination of Jupiter's mass from Juno radio tracking data, Journal of Guidance, Control, and Dynamics 44, 5. https://doi.org/10.2514/1.G005311
Moirano, A., L. Gomez Casajus, M. Zannoni, D. Durante, and P. Tortora (2021). Morphology of the Io Plasma Torus from Juno Radio Occultations, Journal of Geophysical Research: Space Physics 126, e2021JA029190. https://doi.org/10.1029/2021JA029190
Parisi, M., Y. Kaspi, E. Galanti, D. Durante, S.J. Bolton, S.M. Levin, et al. (2021). The depth of Jupiter’s Great Red Spot constrained by the Juno gravity overflights, Science 374, 964–968. https://doi.org/10.1126/science.abf1396
Miguel, Y., M. Bazot, T. Guillot, S. Howard, E. Galanti, Y. Kaspi, et al. (2022). Jupiter’s inhomogeneous envelope, Astronomy and Astrophysics 662, A18. https://doi.org/10.1051/0004-6361/202243207
Durante, D., T. Guillot, L. Iess, D.J. Stevenson, C.R. Mankovich, S. Markham, et al. (2022). Juno spacecraft gravity measurements provide evidence for normal modes of Jupiter, Nature Communications 13, 4632. https://doi.org/10.1038/s41467-022-32299-9
Gomez Casajus, L., A.I. Ermakov, M. Zannoni, J.T. Keane, D. Stevenson, et al. (2022). The gravity field of Ganymede after the Juno’s extended mission, Geophysical Research Letters 49, e2022GL099475. https://doi.org/10.1029/2022GL099475
Kaspi, Y., E. Galanti, R. Park, K. Duer, N. Gavriel, D. Durante, et al. (2023). Observational evidence for cylindrically oriented zonal flows on Jupiter. Nature Astronomy 7, 1463-1472, https://doi.org/10.1038/s41550-023-02077-8
Lari, G., M. Zannoni, D. Durante, R. Park, and G. Tommei (2024). Determination of Jupiter’s pole orientation from Juno radio science data, Aerospace 11(2), 124. https://doi.org/10.3390/aerospace11020124
Durante, D., P. Cappuccio, I. Di Stefano, M. Zannoni, L. Gomez Casajus, et al. (2024). Testing general relativity with Juno at Jupiter. The Astrophysical Journal 971(2), 145. https://doi.org/10.3847/1538-4357/ad5ff5
Park. R.S., R.A. Jacobson, L. Gomez Casajus, F. Nimmo, J.T. Keane, A.I Ermakov, et al. (2025). Io’s tidal response precludes a shallow magma ocean. Nature 638, 69–73. https://doi.org/10.1038/s41586-024-08442-5