The 2021 mutual phenomena involving the Galilean satellites of Jupiter and the inner satellite Thebe

TL;DR

This paper reports on the 2021 mutual phenomena observations of Jupiter's Galilean satellites and Thebe, providing precise astrometric data that improve orbital models and contribute to ephemeris accuracy.

Contribution

It presents new measurements of mutual events involving Galilean satellites and Thebe, including only the second published eclipse of Thebe, enhancing orbital data accuracy.

Findings

Average positional uncertainty of 5 mas for Galilean satellites.

First detailed measurement of Thebe eclipse in recent literature.

Added 17% more mutual events to existing datasets.

Abstract

Astrometric studies and orbital modeling of planetary moons have contributed significantly to advancing our understanding of their orbital dynamics. These studies require precise positions measured over extended periods. In this paper, we present the results of the 2021 Brazilian Jovian mutual phenomena campaign. The data correspond to eight events between Galilean satellites, in addition to a rare eclipse of Thebe, an inner satellite, totaling nine events. A geometric model along with the DE440/JUP365 ephemerides was used to reproduce the events and simulate the light curves. A Monte Carlo method and chi-squared statistics were used to fit the simulated light curves to the observations. The reflectance model adopted for our simulations was the complete version of the Oren-Nayer model. The average uncertainty of the relative positions of the Galilean satellites was 5 mas (15 km) and for the inner Thebe satellite 32 mas (96 km). The seven mutual events (nine independent observations) here analyzed represent and addition of 17% events (10% light curves) with respect to the PHEMU21 international campaign. Furthermore, our result of Thebe eclipse is only the second measurement published to date. Our results contribute to the ephemeris database, being fundamental to improving satellite orbits and thus minimizing their uncertainties.