Annales Geophysicae
ISSN 0992-7689
2026
Shared — curated by The Gufo editorial team

Juice/SWI during the Lunar-Earth-Gravity-Assist (LEGA) – Part 4: Antenna pointing and beam characterisation

R. Moreno*, L. Rezac, Tomáš Formánek, Thibault Cavalié, C. Jarchow, E. Lellouch, P. Hartogh, Axel Murk, Mikko Kotiranta, Alberto Carrasco Gallardo, Samuel Goodyear, Ali Schulz-Ravanbakhsh, B. Dąbrowski, F. Herpin, Yasuko J. Kasai, Donal P. Murtagh, Michael Olberg, M. Rengel, Hideo Sagawa, S. Szutowicz, Eva Wirström

LIRA - Laboratoire d'instrumentation et de recherche en astrophysique · Max Planck Institute for Solar System Research · Centre National de la Recherche Scientifique; Université Paris Cité; Université Paris Sciences et Lettres; Observatoire de Paris; Sorbonne Université · Centre National de la Recherche Scientifique; Université de Bordeaux; Laboratoire d'Astrophysique de Bordeaux · University of Bern · Institute of Science Tokyo; National Institute of Information and Communications Technology · Chalmers University of Technology · Kyoto Sangyo University · Centrum Badań Kosmicznych; Polish Academy of Sciences

Received: 2026-11-02 · Published: 2026-10-30

© 2026 The Author(s) and the original publisher.

CC BY 4.0 This work is licensed under a Creative Commons Attribution 4.0 International License.
Curated by The Gufo editorial team.

Originally published in Annales Geophysicae, 2026 — https://doi.org/10.5194/angeo-44-1227-2026.

Original title
Juice/SWI during the Lunar-Earth-Gravity-Assist (LEGA) – Part 4: Antenna pointing and beam characterisation
Authors
R. Moreno, L. Rezac, Tomáš Formánek, Thibault Cavalié, C. Jarchow, E. Lellouch, P. Hartogh, Axel Murk, Mikko Kotiranta, Alberto Carrasco Gallardo, Samuel Goodyear, Ali Schulz-Ravanbakhsh, B. Dąbrowski, F. Herpin, Yasuko J. Kasai, Donal P. Murtagh, Michael Olberg, M. Rengel, Hideo Sagawa, S. Szutowicz, Eva Wirström
Source journal
Annales Geophysicae
Published
2026-10-30
Licence
Creative Commons Attribution 4.0 International
Original
https://doi.org/10.5194/angeo-44-1227-2026

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Abstract

Abstract. The Submillimetre Wave Instrument (SWI) onboard the Jupiter Icy Moons Explorer (Juice) spacecraft consists of a 29 cm off-axis paraboloid antenna and two double-sideband heterodyne receivers operating in the frequency ranges of 530–638 and 1066–1286 GHz. This instrument is designed to study Jupiter’s atmosphere and the exospheres of the Galilean moons. We used the Lunar-Earth-Gravity-Assist (LEGA) data from August 2024 to characterise this antenna using several SWI observations pointing towards the Earth. The data analysis of the LEGA observations dedicated to the antenna beam allows us to characterise the antenna beam Full Width at Half Maximum (FWHM), sidelobes, absolute pointing and receiver coalignement. Moreover, an estimate of the calibration efficiency factor has been obtained.

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Editor’s summary (commentary by The Gufo, not part of the original work)

This paper reports on calibration tests of the Submillimetre Wave Instrument (SWI) aboard the Juice spacecraft, conducted during its Lunar-Earth-Gravity-Assist manoeuvre in August 2024. SWI is designed to study Jupiter's atmosphere and the exospheres of its icy moons using a parabolic antenna and two heterodyne receivers operating at submillimetre wavelengths. By pointing the instrument at Earth during the flyby, the team measured key performance characteristics: the shape and width of the antenna's beam, the strength of unwanted sidelobes, how accurately the instrument points, and how well its two receivers are aligned with each other. They also derived an estimate of the instrument's calibration efficiency. These in-flight measurements help confirm that SWI performs as expected before it reaches Jupiter, ensuring that future scientific observations can be properly interpreted.

Why it matters: These in-flight calibration results validate the performance of a key instrument that will study Jupiter's atmosphere and moons during the Juice mission, informing how its future data should be interpreted.

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