On the contribution of PRIDE-JUICE to Jovian system ephemerides

Dynamical modelling of the Galilean moons for the JUICE mission

755 new CCD observations during the years 2014-2016 have been reduced to derive the precise positions of Triton, the first satellite of Neptune. The observations were made by the 1-m telescope at Yunnan Observatory over 15 nights. The positions of Triton are measured with respect to the stars in Gaia DR1 star catalogue. The theoretical position of Triton was retrieved from the Jet Propulsion Laboratory (JPL) Horizons System that includes the satellite ephemeris nep081xl, while the position of Neptune was obtained from the JPL ephemeris DE431mx. Our results show that the mean (O - C)s (observed minus computed) are 0.042 and -0.006 arcsec in right ascension and declination, respectively. The dispersions of our observations are estimated at about 0.012 arcsec in each direction.

Precise CCD positions of Triton in 2014–2016 using the newest Gaia DR1 star catalogue

The third data release by the Gaia mission of the European Space (DR3) is the first release to provide the community with a large sample of observations for more than 150 thousand Solar System objects, including asteroids and natural planetary satellites. The release contains astrometry (over 23 million epochs) and photometry, along with average reflectance spectra of 60518 asteroids and osculating elements. We present an overview of the procedures that have been implemented over several years of development and tests to process Solar System data at the level of accuracy that Gaia can reach. We illustrate the data properties and potential with some practical examples. In order to allow the users of DR3 to best exploit the data, we explain the assumptions and approaches followed in the implementation of the data processing pipeline for Solar System processing, and their effects in terms of data filtering, optimisation, and performances. We then test the data quality by analysing post-fit residuals to adjusted orbits, the capacity of detecting subtle dynamical effects (wobbling due to satellites or shape and Yarkovsky acceleration), and to reproduce known properties of asteroid photometry (phase curves and rotational light curves). The DR3 astrometric accuracy is a clear improvement over the data published in DR2, which concerned a very limited sample of asteroids. The performance of the data reduction is met, and is illustrated by the capacity of detecting milliarcsecond-level wobbling of the asteroid photocentre that is due to satellite or shape effects and contributes to Yarkovsky effect measurements. The third data release can in terms of data completeness and accuracy be considered the first full-scale realisation of the Solar System survey by Gaia.

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Gaia Data Release 3: The Solar System survey

Context. The photometry of mutual occultations and eclipses of natural planetary satellites can be used to infer very accurate astrometric data. This can be achieved by processing the light curves of the satellites observed during international campaigns of photometric observations of these mutual events. Aims. This work focuses on processing the complete database of photometric observations of the mutual occultations and eclipses of the Uranian satellites made during the international campaign in 2007. The final goal is to derive new accurate astrometric data. Methods. We used an accurate photometric model of mutual events that explicitly depends on parameters that these accurate observations should be sensitive to, including the albedos of the satellites. Our original method is applied to derive astrometric data in relative positions from photometric observations of mutual occultations and eclipses of the Uranian satellites. Results. We process the 41 light-curves obtained during the international campaign of photometric observations of the Uranian satellites in 2007. The root-mean-square (rms) of the residuals “observations minus calculations” (O‐C) with respect to theory for the best 34 observations are equal to 10.3 and 17.7 mas in right ascension and declination, respectively. For five observations only the position angle was derived. Topocentric or heliocentric angular differences for satellites pairs were obtained from 25 central instant offsets between observation and theory during the time period from May 4, 2007 to January 4, 2008. Conclusions. The rms of the residuals is from 10 to 20 mas that corresponds in situ to 10 to 20 km. These mutual event observations appear to be the most accurate astrometric ground-based observations of the major Uranian satellites to-date and should be used for dynamical purposes.

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Astrometric results of observations of mutual occultations and eclipses of the Uranian satellites in 2007

http://www.oca.eu/workshop/Pise/slides/arlot-pisa-2011.pdf

The astrometry of the natural planetary satellites applied to their dynamics before and after Gaia

Natural satellites mutual phenomena observations: Achievements and future

https://www.lesia.obspm.fr/perso/bruno-sicardy/biblio/biblio/Arlot_sicardy_pheura_PSS08.pdf

Predictions and observations of events and configurations occurring during the Uranian equinox

Aims. During the 2014–2015 campaign of mutual events, we recorded ground-based photometric observations of eclipses of Amalthea (JV) and, for the first time, Thebe (JXIV) by the Galilean moons. We focused on estimating whether the positioning accuracy of the inner satellites determined with photometry is sufficient for dynamical studies.Methods. We observed two eclipses of Amalthea and one of Thebe with the 1 m telescope at Pic du Midi Observatory using an IR filter and a mask placed over the planetary image to avoid blooming features. A third observation of Amalthea was taken at Saint-Sulpice Observatory with a 60 cm telescope using a methane filter (890 nm) and a deep absorption band to decrease the contrast between the planet and the satellites. After background removal, we computed a differential aperture photometry to obtain the light flux, and followed with an astrometric reduction.Results. We provide astrometric results with an external precision of 53 mas for the eclipse of Thebe, and 20 mas for that of Amalthea. These observation accuracies largely override standard astrometric measurements. The (O − C)s for the eclipse of Thebe are 75 mas on the X -axis and 120 mas on the Y -axis. The (O − C)s for the total eclipses of Amalthea are 95 mas and 22 mas, along the orbit, for two of the three events. Taking into account the ratio of (O − C) to precision of the astrometric results, we show a significant discrepancy with the theory established by Avdyushev and Ban’shikova in 2008, and the JPL JUP 310 ephemeris.

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Jean-Eudes Arlot

Papers

The astrometry of the natural planetary satellites applied to their dynamics before and after Gaia

Natural satellites mutual phenomena observations: Achievements and future

Predictions and observations of events and configurations occurring during the Uranian equinox

Eclipses of the inner satellites of Jupiter observed in 2015

Astrometric results PHEMU-1985 and PHEMU-1991