Speaker
Dr
Davide Silvestri
(University of Bologna)
Description
The BepiColombo mission is finally approaching the last phase, preceding its launch, which will bring the spacecraft to its final destination, planet Mercury, around which the probe will start its one year nominal mission in 2024.
In-orbit investigations are a privileged condition for exploring a planet, and Mercury has demonstrated to be a fascinating destination since Mariner 10 first unveiled some of its mysteries. MESSENGER disclosed several questions but also arose other interrogatives and much is still to be discovered.
One of the objectives of the BepiColombo Radio science Experiment is the study of Mercury’s core. Since a strict connection exists between core and rotational state, measurements of Mercury’s obliquity and librations at unprecedented accuracies became one the main purposes of MORE (Mercury Orbiter Radio science Experiment) rotation experiment.
The rotation experiment will be accomplished thanks to the cooperation among different payloads: precise orbit determination data will be derived from MORE and high resolution images will be provided by HRIC, part of the SYMBIO-SYS payload.
An end-to-end simulator has been built up employing the camera images as the primary observables with the final aim of defining their optimal acquisition scheduling. In this simulator the images are employed to correlate surface landmarks extrapolated by pictures of the same area taken at different epochs: their displacement in time represents the observable to be fed into an estimation process for deriving Mercury’s rotation parameters.
An extensive simulation campaign has been performed leading to the identification of the most favorable observational strategy and location of the landmarks on the surface so as to fulfill accuracies lower than 1 arcsecond for both obliquity and libration estimation.
Concurrently an Orbit Determination simulation scenario for MPO has been set, in which high fidelity, but still evolving, models are implemented to consider all possible degradation effects. The setup consider an on-board accelerometer error model, simulating ISA instrument, errors in the radiometric and optical observables and a full gravity field implementation to degree and order 30 and tidal love number $k_2$.
A pure multiarc orbit determination filter provides the simulated trajectory, the computation of simulated observables and then estimates the whole global and local parameters in the play providing direct insight on mission performances. This architecture has been exploited for the evaluation of the difference in performance by using a random generated set of observation locations or an optimized set for optical observables focusing in the achievable uncertainty in the orientation parameters, in particular for what concern the Mercury obliquity $\varepsilon$ and amplitude in longitudinal libration $\Phi_0$ validating the optimization approach.
| Applicant type | First author |
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Primary author
Dr
Davide Silvestri
(University of Bologna)
Co-authors
Dr
Alessandra Palli
(University of Bologna)
Prof.
Paolo Tortora
(University of Bologna)
