On the determination of Jupiter's satellite-dependent Love numbers from Juno gravity data

The Juno gravity experiment, among the nine instruments onboard the spacecraft, is aimed at studying the interior structure of Jupiter to gain insight into its formation. Doppler data collected during the first two gravity-dedicated orbits completed by Juno around the gas giant have already provided a measurement of Jupiter's gravity field with outstanding accuracy, answering crucial questions about its interior composition. The large dataset that will be collected throughout the remaining phases of the mission until the end in July 2021 might allow to determine Jupiter's response to the satellite-dependent tidal perturbation raised by its moons, and even to separate the static and dynamic effects. We report on numerical simulations performed over the full science mission to assess the sensitivity of Juno gravity measurements to satellite-dependent tides on Jupiter. We assumed a realistic simulation scenario that is coherent with the result of data analysis from the first gravity passes. Furthermore, we implemented a satellite-dependent tidal model within the dynamical model used to fit the simulated Doppler data. The formal uncertainties resulting from the covariance analysis show that Juno is indeed sensitive to satellite-dependent tides on Jupiter raised by the inner Galilean satellites (the static Love numbers of degree and order 2 of Io, Europa and Ganymede can be determined respectively to 0.28%, 4.6% and 5.3% at 1 sigma). This unprecedented determination, that will be carried out towards the end of the mission, could further constrain the interior structure of the planet, allowing to discern among interior models and improving existing theories of planetary tidal response

Generation and reduction of the data for the Ulysses gravitational wave experiment

A procedure for the generation and reduction of the radiometric data known as REGRES is described. The software is implemented on a HP-1000F computer and was tested on REGRES data relative to the Voyager I spacecraft. The REGRES data are a current output of NASA's Orbit Determination Program. The software package was developed in view of the data analysis of the gravitational wave experiment planned for the European spacecraft Ulysses

On the determination of post-Newtonian parameters with BepiColombo radio science experiment

One of the main goals of the Mercury Orbiter Radio science Experiment (MORE), onboard the ESA-JAXA BepiColombo mission to Mercury, is to perform a test of gravitational theories by means of high precision radio-observables, constraining several Post-Newtonian (PN) parameters. This will be performed in two steps: (i) with a superior solar conjunction experiment during the cruise phase of the mission; (ii) by reconstructing the orbit of Mercury around the Sun once the spacecraft will be arrived at Mercury. In this work we present the results of numerical simulations of the MORE relativity experiment, carried out in a realistic scenario, showing how the experiment can improve over current estimates

Hardware prototyping and validation of a W-ΔDOR digital signal processor

Microwave tracking, usually performed by on ground processing of the signals coming from a spacecraft, represents a crucial aspect in every deep-space mission. Various noise sources, including receiver noise, affect these signals, limiting the accuracy of the radiometric measurements obtained from the radio link. There are several methods used for spacecraft tracking, including the Delta-Differential One-Way Ranging (ΔDOR) technique. In the past years, European Space Agency (ESA) missions relied on a narrowband ΔDOR system for navigation in the cruise phase. To limit the adverse effect of nonlinearities in the receiving chain, an innovative wideband approach to ΔDOR measurements has recently been proposed. This work presents the hardware implementation of a new version of the ESA X/Ka Deep Space Transponder based on the new tracking technique named Wideband ΔDOR (W-ΔDOR). The architecture of the new transponder guarantees backward compatibility with narrowband ΔDOR

Is it possible to measure the Lense-Thirring effect on the orbits of the planets in the gravitational field of the Sun?

Here we explore a novel approach in order to try to measure the post-Newtonian 1/c^2 Lense-Thirring secular effect induced by the gravitomagnetic field of the Sun on the planetary orbital motion. Due to the relative smallness of the solar angular momentum J and the large values of the planetary semimajor axes a, the gravitomagnetic precessions, which affect the nodes Omega and the perihelia omega and are proportional to J/a^3, are of the order of 10^-3 arcseconds per century only for, e.g., Mercury. This value lies just at the edge of the present-day observational sensitivity in reconstructing the planetary orbits, although future missions to Mercury like Messenger and BepiColombo could allow to increase it. The major problems come from the main sources of systematic errors. They are the aliasing classical precessions induced by the multipolar expansion of the Sun's gravitational potential and the classical secular N-body precessions which are of the same order of magnitude or much larger than the Lense-Thirring precessions of interest. This definitely rules out the possibility of analyzing only one orbital element of, e.g., Mercury. In order to circumvent these problems, we propose a suitable linear combination of the orbital residuals of the nodes of Mercury, Venus and Mars which is, by construction, independent of such classical secular precessions. A 1-sigma reasonable estimate of the obtainable accuracy yields a 36% error. Since the major role in the proposed combination is played by the Mercury's node, it could happen that the new, more accurate ephemerides available in future thanks to the Messenger and BepiColombo missions will offer an opportunity to improve the present unfavorable situation.Comment: LaTex2e, A&A macros, 6 pages, no figure, 3 tables. Substantial revision. More realistic conclusions. Estimations of the impact of BepiColombo presente

New constraints on the location of P9 obtained with the INPOP19a planetary ephemeris

Context. We used the new released INPOP19a planetary ephemerides benefiting from Jupiter-updated positions by the Juno mission and reanalyzed Cassini observations. Aims. We test possible locations of the unknown planet P9. To do this, we used the perturbations it produces on the orbits of the outer planets, more specifically, on the orbit of Saturn. Methods. Two statistical criteria were used to identify possible acceptable locations of P9 according to (i) the difference in planetary positions when P9 is included compared with the propagated covariance matrix, and (ii) the χ2 likelihood of postfit residuals for ephemerides when P9 is included. Results. No significant improvement of the residuals was found for any of the simulated locations, but we provide zones that induce a significant degradation of the ephemerides. Conclusions. Based on the INPOP19a planetary ephemerides, we demonstrate that if P9 exists, it cannot be closer than 500 AU with a 5 M⊕ and no closer than 650 AU with a 10 M⊕ . We also show that there is no clear zone that would indicate the positive existence of planet P9, but there are zones for which the existence of P9 is compatible with the 3σ accuracy of the INPOP planetary ephemerides

Analysis of Cassini radio tracking data for the construction of INPOP19a: a new estimate of the Kuiper belt mass

Context. Recent discoveries of new trans-Neptunian objects have greatly increased the attention by the scientific community to this relatively unknown region of the solar system. The current level of precision achieved in the description of planet orbits has transformed modern ephemerides in the most updated tools for studying the gravitational interactions between solar system bodies. In this context, the orbit of Saturn plays a primary role, especially thanks to Cassini tracking data collected during its 13-year mission around the ringed planet. Planetary ephemerides are currently mainly built using radio data, in particular with normal points derived from range and Doppler observables exchanged between ground stations and interplanetary probes. Aims. We present an analysis of Cassini navigation data aimed at producing new normal points based on the most updated knowledge of the Saturnian system developed throughout the whole mission. We provide additional points from radio science dedicated passes of Grand Finale orbits and Titan flybys. An updated version of the INPOP planetary ephemerides based upon these normal points is presented, along with a new estimate of the mass of trans-Neptunian object rings located in the 2:1 and 3:2 mean motion resonances with Neptune. Methods. We describe in detail the orbit determination process performed to construct the normal points and their associated uncertainties and how we process those points to produce a new planetary ephemeris. Results. From the analysis, we obtained 623 new normal points for Saturn with metre-level accuracy. The ephemeris INPOP19a, including this new dataset, provides an estimated mass for the trans-Neptunian object rings of (0.061  ±  0.001)M⊕

Light-time computations for the BepiColombo radioscience experiment

The radioscience experiment is one of the on board experiment of the Mercury ESA mission BepiColombo that will be launched in 2014. The goals of the experiment are to determine the gravity field of Mercury and its rotation state, to determine the orbit of Mercury, to constrain the possible theories of gravitation (for example by determining the post-Newtonian (PN) parameters), to provide the spacecraft position for geodesy experiments and to contribute to planetary ephemerides improvement. This is possible thanks to a new technology which allows to reach great accuracies in the observables range and range rate; it is well known that a similar level of accuracy requires studying a suitable model taking into account numerous relativistic effects. In this paper we deal with the modelling of the space-time coordinate transformations needed for the light-time computations and the numerical methods adopted to avoid rounding-off errors in such computations.Comment: 14 pages, 7 figures, corrected reference