The 2014–2015 Brazilian mutual phenomena campaign for the Jovian satellites and improved results for the 2009 events

Abstract

A B S T R A C TProgress in astrometry and orbital modelling of planetary moons in the last decade enabled better determinations of their orbits. These studies need accurate positions spread over extended periods. We present the results of the 2014-2015 Brazilian campaign for 40 mutual events from 47 observed light curves by the Galilean satellites plus one eclipse of Amalthea by Ganymede. We also reanalysed and updated results for 25 mutual events observed in the 2009 campaign.All telescopes were equipped with narrow-band filters centred at 889 nm with a width of 15 nm to eliminate the scattered light from Jupiter. The albedos' ratio was determined using images before and after each event. We simulated images of moons, umbra, and penumbra in the sky plane, and integrated their fluxes to compute albedos, simulate light curves and fit them to the observed ones using a chi-square fitting procedure. For that, we used the complete version of the Oren-Nayer reflectance model. The relative satellite positions mean uncertainty was 11.2 mas (∼35 km) and 10.1 mas (∼31 km) for the 2014-2015 and 2009 campaigns respectively. The simulated and observed ASCII light curve files are freely available in electronic form at the Natural Satellites DataBase (NSDB).The 40/25 mutual events from our 2014-2015/2009 campaigns represent a significant contribution of 17%/15% in comparison with the PHEMU campaigns lead by the IMCCE. Besides that, our result for the eclipse of Amalthea is only the 4 ℎ such measurement ever published after the three ones observed by the 2014-2015 international PHEMU campaign. Our results are suitable for new orbital/ephemeris determinations for the Galilean moons and Amalthea.

Analytic Light Curves in Reflected Light: Phase Curves, Occultations, and Non-Lambertian Scattering for Spherical Planets and Moons

“…The shape of secondary eclipse, however, is relatively insensitive to the point-source approximation (see Figure 8). 18 model of Oren & Nayar (1994), commonly used in computer graphics applications and solar system body modeling (e.g., Morgado et al 2019). In this model, the surface is treated as a collection of a large number of Lambertian facets oriented at random angles relative to the average surface normal, whose net contribution to the total intensity can depart significantly from the Lambertian case.…”

“…Thus far, these have been studied primarily within our solar system. Mutual occultations among the Galilean moons of Jupiter have been extensively studied to infer surface properties of the moons and to refine their ephemerides (e.g., Arlot et al 1974Arlot et al , 2014Aksnes et al 1984;de Kleer et al 2017;Saquet et al 2018;Morgado et al 2019;Bartolić et al 2022). Farther out in the solar system, mutual occultations of Pluto and Charon in the late 1980s were used to confirm Charon's existence (Stern 1992), establish the sizes and orbital parameters of the two bodies (Tholen & Buie 1990), and infer their surface properties (Marcialis 1990).…”

Analytic Light Curves in Reflected Light: Phase Curves, Occultations, and Non-Lambertian Scattering for Spherical Planets and Moons

“…Treatment of a generalized, flexible scattering model is beyond the scope of this paper; see Heng et al (2021) for recent results on this front. However, as an example of how a scattering model may be incorporated into the starry algorithm, we consider in detail the case of the rough surface scattering model of Oren & Nayar (1994), commonly used in computer graphics applications and solar system body modeling (e.g., Morgado et al 2019). In this model, the surface is treated as a collection of a large number of Lambertian facets oriented at random angles relative to the average surface normal, whose net contribution to the total intensity can depart significantly from the Lambertian case.…”

“…Thus far, these have been studied primarily within our solar system. Mutual occultations among the Galilean moons of Jupiter have been extensively studied to infer surface properties of the moons and to refine their ephemerides (e.g., Arlot et al 1974;Aksnes et al 1984;Arlot et al 2014;de Kleer et al 2017;Saquet et al 2018;Morgado et al 2019;Bartolić et al 2021). Farther out in the solar system, mutual occultations of Pluto and Charon in the late 1980s were used to confirm Charon's existence (Stern 1992), establish the sizes and orbital parameters of the two bodies (Tholen & Buie 1990), and infer their surface properties (Marcialis 1990).…”

Milliarcsecond Astrometry for the Galilean Moons Using Stellar Occultations

“…The case of Galilean moons is a critical example because Jupiter's brightness in the Field of View (FoV) would quickly saturate the CCD, thus providing positions with uncertainties that range between 100 and 150 milliarcseconds (mas; Kiseleva et al 2008). This scenario motivates the search for alternative methods for the astrometry of these satellites, such as the mutual phenomena events (Aksnes & Franklin 1976;Aksnes et al 1984;Emelyanov 2009;Arlot et al 2014;Saquet et al 2018;Morgado et al 2019c, and references therein), mutual approximations (Morgado et al 2016(Morgado et al , 2019a, radar astrometry (Brozović et al 2020), and stellar occultations (Morgado et al 2019b), among others.…”