David M. Lucchesi

The LARES mission revisited: an alternative scenario

In the original LARES mission, the general relativistic Lense–Thirring effect was to be detected using as an observable the sum of the residuals of the nodes of the existing passive geodetic laser-ranged LAGEOS satellite and of its proposed twin LARES. The proposed nominal orbital configuration of the latter would reduce the systematic error due to the mismodelling in the even zonal harmonics of the geopotential, which is the main source of error (to 0.3%) according to the most recent Earth gravity model EGM96. This observable turns out to be sensitive to possible departures of the LARES orbital parameters from their nominal values due to the orbital injection errors. By adopting a suitable combination of the orbital residuals of the nodes of LAGEOS, LAGEOS II and LARES and the perigees of LAGEOS II and LARES, it should be possible to reduce the error due to the geopotential by one order of magnitude, according to the EGM96 model. Moreover, the sensitivity to the orbital injection errors should be greatly reduced. According to a preliminary estimate of the error budget, the total error of the experiment should be reduced to less than 1%. In the near future, when the new data on the terrestrial gravitational field from CHAMP and GRACE missions become available, a further increase in the accuracy should be obtained. The proposal to place LARES in a polar 2000 km altitude orbit and consider only its nodal rate would present the drawback that even small departures from the polar geometry would yield notable errors due to the mismodelled even zonal harmonics of the geopotential, according to the EGM96 model.

The comparative exploration of the ice giant planets with twin spacecraft: Unveiling the history of our Solar System

Abstract In the course of the selection of the scientific themes for the second and third L-class missions of the Cosmic Vision 2015–2025 program of the European Space Agency, the exploration of the ice giant planets Uranus and Neptune was defined “a timely milestone, fully appropriate for an L class mission”. Among the proposed scientific themes, we presented the scientific case of exploring both planets and their satellites in the framework of a single L-class mission and proposed a mission scenario that could allow to achieve this result. In this work we present an updated and more complete discussion of the scientific rationale and of the mission concept for a comparative exploration of the ice giant planets Uranus and Neptune and of their satellite systems with twin spacecraft. The first goal of comparatively studying these two similar yet extremely different systems is to shed new light on the ancient past of the Solar System and on the processes that shaped its formation and evolution. This, in turn, would reveal whether the Solar System and the very diverse extrasolar systems discovered so far all share a common origin or if different environments and mechanisms were responsible for their formation. A space mission to the ice giants would also open up the possibility to use Uranus and Neptune as templates in the study of one of the most abundant type of extrasolar planets in the galaxy. Finally, such a mission would allow a detailed study of the interplanetary and gravitational environments at a range of distances from the Sun poorly covered by direct exploration, improving the constraints on the fundamental theories of gravitation and on the behavior of the solar wind and the interplanetary magnetic field.

Quantum time delay in the gravitational field of a rotating mass

We examine quantum corrections of time delay arising in the gravitational field of a spinning oblate source. Low-energy quantum effects occurring in Kerr geometry are derived within a framework where general relativity is fully seen as an effective field theory. By employing such a pattern, gravitational radiative modifications of Kerr metric are derived from the energy-momentum tensor of the source, which at lowest order in the fields is modelled as a point mass. Therefore, in order to describe a quantum corrected version of time delay in the case in which the source body has a finite extension, we introduce a hybrid scheme where quantum fluctuations affect only the monopole term occurring in the multipole expansion of the Newtonian potential. The predicted quantum deviation from the corresponding classical value turns out to be too small to be detected in the next future, showing that new models should be examined in order to test low-energy quantum gravity within the solar system.

The BepiColombo Radio Science Experiment and the Non‐Gravitational Perturbations to the Mercury Planetary Orbiter orbit: key role of the Italian Spring Accelerometer

The advantages of an on‐board accelerometer are outlined in the case of the Bepi‐Colombo mission to Mercury with respect to the modeling of the non‐gravitational perturbations at work in the strong radiation environment of Mercury. The readings from the Italian Spring Accelerometer guarantees a very significant reduction of the non‐gravitational accelerations impact on the space mission accuracy, especially of the strong direct solar radiation pressure.