Constraining the Ephemeris and Interior Structure of Io using Space-Based Astrometry by JUICE

Owing to the assumed presence of sub-surface oceans, the Galilean satellites - Io, Europa, Ganymede, and Callisto - are among the most promising candidates for potential extraterrestrial habitats within our Solar System. To this end, the moons are going to be extensively studied by the upcoming JUICE and Europa Clipper missions. Ultimately,...

Gaia Data Release 3: Stellar multiplicity, a teaser for the hidden treasure

Context. The Gaia DR3 catalogue contains, for the first time, about 800 000 solutions with either orbital elements or trend parameters for astrometric, spectroscopic, and eclipsing binaries, and combinations of these three.<br/><br/>Aims. With this paper, we aim to illustrate the huge potential of this large non-single-star catalogue.<br/><br/...

Gaia Data Release 3: Summary of the content and survey properties

Context. We present the third data release of the European Space Agency's Gaia mission, Gaia DR3. This release includes a large variety of new data products, notably a much expanded radial velocity survey and a very extensive astrophysical characterisation of Gaia sources. Aims. We outline the content and the properties of Gaia DR3, providing...

Combining astrometry and JUICE-Europa Clipper radio science to improve the ephemerides of the Galilean moons

Context. The upcoming JUICE and Europa Clipper missions targeting Jupiter s Galilean satellites will provide radio science tracking measurements of both spacecraft. Such data are expected to significantly help estimating the moons ephemerides and related dynamical parameters (e.g. tidal dissipation parameters). However, the two missions will...

Gaia Early Data Release 3: The celestial reference frame (Gaia-CRF3)

Context. Gaia-CRF3 is the celestial reference frame for positions and proper motions in the third release of data from the Gaia mission, Gaia DR3 (and for the early third release, Gaia EDR3, which contains identical astrometric results). The reference frame isdefined by the positions and proper motions at epoch 2016.0 for a specific set of...

Analytical framework for mutual approximations: Derivation and application to Jovian satellites

Context. The apparent close encounters of two satellites in the plane of the sky, called mutual approximations, have been suggested as a different type of astrometric observation to refine the moons' ephemerides. The main observables are then the central instants of the close encounters, which have the advantage of being free of any scaling...

Optimizing the observation schedule of the JANUS instrument to improve the Jovian system ephemerides

The Jupiter Icy moons Explorer (JUICE) will generate ephemerides of the Galilean moons to assess their ability to sustain live. However, determining the ephemerides only using radiometric tracking (acquired using PRIDE and 3GM) results in an unstable solution which is related to the absence of flybys of especially Io, such that its dynamics can...

RadioAstron as a target and as an instrument: Enhancing the Space VLBI mission’s scientific output

Context. The accuracy of orbit determination has a strong impact on the scientific output of the Space VLBI mission RadioAstron. Aims. The aim of this work is to improve the RadioAstron orbit reconstruction by means of sophisticated dynamical modelling of its motion in combination with multi-station Doppler tracking of the RadioAstron spacecraft...

Observations and analysis of phase scintillation of spacecraft signal on the interplanetary plasma

Aims. The phase scintillation of the European Space Agency’s Venus Express (VEX) spacecraft telemetry signal was observed at X-band (? = 3.6 cm) with a number of radio telescopes of the European Very Long Baseline Interferometry (VLBI) Network in the period 2009–2013. Methods. We found a phase fluctuation spectrum along the Venus orbit with a...

Spacecraft VLBI and Doppler tracking: Algorithms and implementation

Aims. We present the results of several multi-station Very Long Baseline Interferometry (VLBI) experiments conducted with the ESA spacecraft Venus Express as a target. To determine the true capabilities of VLBI tracking for future planetary missions in the solar system, it is necessary to demonstrate the accuracy of the method for existing...