348 research outputs found
First NGP measurements at Mercury
No full textISA (Italian Spring Accelerometer) is a scientific payload of the Mercury Planetary Orbiter (MPO) module of the ESA/JAXA BepiColombo mission to planet Mercury and it is the first high-sensitivity accelerometer on-board an interplanetary spacecraft. It will be one of the key instruments to perform Radio Science Experiments during the orbital phase. The instrument is sensitive to any acceleration, greater than 10-8 ms-2Hz-1/2, perturbing the free fall of the spacecraft in the overall gravity field. The main goal of ISA is indeed to measure the so-called Non Gravitational Perturbations (NGP) allowing to reconstruct, a posteriori, the motion of the spacecraft on a geodesic of spacetime. During the first Mercury flyby, performed in October 2021, the spacecraft approached the target planet reaching an altitude above its surface of only 200 km. Thanks to this very low altitude and to the ISA on-board position in cruise configuration, far away from the center of mass of the overall composite spacecraft, the accelerometer has been able to clearly detect the gravity gradient accelerations. Indeed, this is the first direct measurement of the gravity gradient acceleration induced on a spacecraft by the gravity field of a celestial object different from the Earth. Near the closest approach to the planet, the spacecraft entered in eclipse, losing the effect of the solar radiation pressure acting on its surfaces exposed to the Sun. As a consequence, a sudden change of the acceleration was clearly detected by the accelerometer; the measured signal has a magnitude aligned with the expectations, computed considering optical coefficients and spacecraft attitude. In June 2022, BepiColombo will carry out a second flyby that will be very similar, in terms of altitude, attitude and B-plane coordinates, to the first one, representing an almost unique opportunity to compare two similar measurements
Characterization of the outgassing event during BepiColombo second Venus flyby using italian spring accelerometer data
No full textThe BepiColombo ESA-JAXA mission, launched on October 20, 2018, is scheduled to reach Mercury in
November 2026. The Mercury Composite Spacecraft comprises three modules: the Mercury Planetary Orbiter,
the Mercury Magnetospheric Orbiter, and the Mercury Transfer Module. Currently, BepiColombo is in its
seven-year cruise phase, having completed one Earth flyby, two Venus flybys, and three Mercury flybys.
The spacecraft is equipped with the high-accuracy Italian Spring Accelerometer, capable of measuring nongravitational acceleration variations at frequencies between [3× 10−5
, 10−1] Hz. Interpreting accelerometer data
can be challenging due to overlapping dynamic effects. During the second Venus flyby, the accelerometer
data revealed significant signatures of the gravity gradient signal induced by the planet on the proof masses.
Notably, a large, unexpected acceleration spike was detected near the closest approach, lasting a few minutes.
Further analysis determined that this spike was most likely caused by outgassing from the Mercury Planetary
Orbiter radiator. This paper analyzes the Italian Spring Accelerometer data from the second Venus flyby,
focusing on the unexpected acceleration spike. By combining the torque data from the reaction wheel with
accelerometer data, the team was able to estimate the outgassing location, confirming it as the spacecraft
radiator. Additionally, data from the Mass Spectrum Analyzer sensor, part of the Mercury Plasma Particle
Experiment, suggest that H2O outgassing occurred. The estimated mass of sublimated water is approximately
2 grams
First detection of Non-Gravitational accelerations at Mercury
No full textThe Italian Spring Accelerometer (ISA) is a scientific payload on-board the MPO module of BepiColombo, an ESA's cornerstone mission in collaboration with JAXA, scheduled to arrive at Mercury in December 2025. ISA is the first high-sensitivity accelerometer ever on-board an interplanetary spacecraft. Its main goal is indeed to measure the so-called Non-Gravitational Perturbations (NGP), allowing to reconstruct, a posteriori, the motion of the MPO spacecraft on a geodesic of spacetime. BepiColombo has already performed one flyby at the Earth, two flybys at Venus and two of the six scheduled flybys at Mercury. During these closest approaches, ISA was able to detect the non-gravitational accelerations experienced by the spacecraft. Indeed, during the first flyby at Earth and during both the closest approaches at Mercury, BepiColombo experienced an eclipse phase, who switched off the effect of the Solar Radiation Pressure (SRP) nominally acting on its surfaces exposed to the Sun. Therefore, a sudden change of the acceleration was clearly detected by ISA. The magnitude of this drop is a direct measurement of the SRP acting on the spacecraft. The measured signals have been compared with the expected ones, computed considering optical coefficients of surfaces and spacecraft attitude, showing a good agreement between them. During eclipse phases, ISA was also able to detect the Thermal Recoil Acceleration. Moreover, the acceleration vector of the first Mercury flyby, gathered through ISA measurements, has been inserted, as a posteriori measurement, in the POD by MORE team. Preliminary results show a good accordance between orbit reconstructions calculated using just NGP models and ones using ISA accelerations only. Since the first and the second Mercury flyby were extremely similar, the ISA team was able to compare data coming from both the closest approaches showing a good consistency of the measurements. ISA was also able to measure directly and with good accuracy the Mercury's gravity gradient acting between the accelerometer sensing masses and the spacecraft COM. Thanks to these first in-cruise measurements, the ISA team will be able to better in flight calibrate the instrument. Moreover, collected data will be useful to improve the accuracy of the POD, replacing the mathematical models used for NGPs
Simulation of a pseudo drag-free system for the BepiColombo radio science experiment using ISA accelerometer data
No full textThe Mercury Orbiter Radioscience Experiment (MORE) onboard the ESA/JAXA BepiColombo mission
aims at determining the gravity field and the rotational state of the planet to provide insights into its
internal structure. The experiment will rely on accurate radiometric data provided by the onboard Ka-band
transponder. The strong non-gravitational perturbations acting on the spacecraft during the orbital phase
and the excellent accuracy of the radiometric observables, point out the necessity to host an accurate
accelerometer onboard the spacecraft. The Italian Spring Accelerometer (ISA) has been selected by ESA
to measure the non-gravitational perturbations with an accuracy of in the frequency band of Hz, providing
MORE with valuable information about the spacecraft dynamic. This work presents a software
implementation of a pseudo drag-free system including the synthetic accelerometer measurements in the
orbit determination process. ISA readings have been simulated adding to the ideal measurements, the
intrinsic noise of the instrument and the contribution due to thermal effects, as per requirements. The
identification of a suitable calibration strategy it’s a key factor to fulfil MORE experiment goals pertaining
to geodesy and geophysics since uncompensated errors in accelerometer data can affect meaningfully the
accuracy of the orbit reconstruction, hence the scientific outcome of the experiment. Perturbative analysis
of the 1-year orbital phase at Mercury points out that the proposed accelerometer calibration strategy
allows obtaining an unbiased solution and compensating for accelerometer errors. The numerical
simulation shows that MORE will be able to measure the Mercury gravity field up to degree and order 30
at all the latitude with a formal uncertainty on the determination of the Love number equal to . The
Mercury rotational state will be determined with a formal uncertainty of 1.68 arcsec and 0.78 arcsec on
the right ascension and declination of the pole, respectively, resulting in a formal uncertainty of 0.012
arcmin on the obliquity
The high sensitivity accelerometer ISA during the BepiColombo spacecraft Earth flyby: data analysis, lessons learned, and expected signals for the next
No full textPseudo-drag-free system simulation for bepicolombo radio science using accelerometer data
No full textThe Mercury Orbiter Radio Science Experiment onboard the European Space Agency/Japan AerospaceExploration Agency (JAXA) BepiColombo mission aims at determining the gravity field and the rotational state ofthe planet to provide insight into its internal structure and at performing tests of general relativity. The experimentwill rely on accurate radiometric data provided by the onboard Ka-band transponder and on measurements of thenonconservative perturbations acting on the spacecraft, provided by the Italian Spring Accelerometer. This paperpresents a software implementation of a pseudo-drag-free system which includes the accelerometer measurements inthe orbit determination process. Numerical simulations focus on the identification of a suitable calibration strategy tofulfill the experiment goals pertaining to geodesy and geophysics. The achievement of the expected scientific resultswill depend meaningfully on the quality of the accelerometer data. Perturbative analysis aided in the identificationof a calibration strategy for the accelerometer data processing that allows obtaining an unbiased solution andcompensating for accelerometer errors
The SaToR-G experiment: testing metric and non-metric theories of gravity in the Earth’s field via laser tracking to geodetic satellites
No full textSatellite Tests of Relativistic Gravity (SaToR-G) is a new experiment in fundamental physics of the National
Scientific Committee 2 (CSN2) of the Italian National Institute for Nuclear Physics (INFN).
The experiment aims at testing gravitation beyond the predictions of Einstein’s Theory of General Relativity
in its weak-field and slow-motion limit, searching for effects foreseen by alternative theories of gravitation
and possibly connected with ‘’new physics’’. The predictions of General Relativity on the orbits of geodetic
satellites, which play the role of test masses, will be compared with those of alternative theories of gravity
both metric and non-metric in their essence. This will allow to test, in addition to other aspects of gravita tion, the field equation of gravity. The natural theoretical framework to test gravitation will be that of the Parameterized Post-Newtonian (PPN) formalism. However, we will also try to apply, as far as possible, the approach suggested by R. H. Dicke more than 50 years ago, usually referred to as the Dicke framework. This is a fairly general framework that allows us to conceive experiments not connected, a priori, with a given physical theory and also provides a way to analyze the results of an experiment under primary hypotheses.
The activities of the experiment related to the development of perturbative models to better determine the dynamics of the orbits of the considered satellites will be presented together with preliminary results on possible
new constraints to alternative theories of gravitation
The Galileo for science (G4S_2.0) project: fundamental physics experiments with the Galileo satellites Doresa and Milena
No full textG4S_2.0 is a new project funded by the Italian Space Agency which aims to perform measurements in the field of Fundamental Physics with the two satellites DORESA and MILENA of the Galileo-FOC constellation. These satellites are characterized by the high eccentricity of their orbits and the accuracy of their atomic clocks. An accurate orbit determination will allow to carry out a series of measurements in the fields of gravitation and cosmology, and the implementation of an inverse relativistic positioning system. After a general introduction to the main objectives of G4S_2.0, the activities developed at IAPS-INAF in Rome will be presented
The Galileo satellites Doresa and Milena and their goals in the field of fundamental physics within the Galileo for science (G4S_2.0) project
No full textThe G4S_2.0 (Galileo for Science) project is a new proposal funded by the Italian Space Agency (ASI) and aims to perform a set of measurements in the field of Fundamental Physics with the two Galileo satellites DORESA and MILENA. Indeed, the accurate analysis of the orbits of these satellites — characterized by a relatively high eccentricity of about 0.16 — and of their clocks — the most accurate orbiting the Earth — allows to test relativistic gravity by comparing the predictions of Einstein's theory of General Relativity with those of other theories of gravitation. After a general introduction to the project objectives, we will present the preliminary activities of G4S_2.0 which are being developed by IAPS-INAF in Rome. The results of G4S_2.0 will be particularly useful for the applications of the Galileo FOC satellites in the fields of space geodesy and geophysics as some of these activities will concern the improvement of the precise orbit determination of the satellites through an enhancement of the dynamic model of their orbits, analyzing, in particular, the modelling of non-conservative forces
Carmelo Bene, a Stuttering War Machine
No full textThis article presents one of the topics raised by the research in progress on the work of the Italian artist Carmelo Bene. The author resumes a relation already made at the beginning of the research between the Benean actorial machine and the Deleuzean-Guattarian war machine, adding elements from an approach of stuttering in Gilles Deleuze, as well as from materials and experiences collected in the field research developed in Italy and France along the last three years. The initial goal of the research was to study the concepts that Carmelo Bene created in scene, seeking a closeness to what was original in his work. From the observation of the multiplicity of Bene’s theoretical and artistic alliances, it became necessary to interrogate and contaminate the research and writing modes themselves, establishing a production by means of fragments and closeness, being this text one of them.Cet article presente l’un des sujets soulevés par la recherche de l’oeuvre de l’artiste italien Carmelo Bene, toujours en cours. L’auteur reprend une relation qu’elle avait faite au début de sa recherche entre la machine actorielle bénéenne et la machine de guerre deleuze-guattarienne, en les ajoutant un abordage du bégayage chez Deleuze et par le biais de matériels et d’expériences recueillis lors de recherches de terrain menées en Italie et en France depuis 2014. La recherche avait comme objectif initial une étude des concepts que Carmelo Bene avait créés sur la scene, en cherchant ce qui était original dans son travail. La connaissance de la multiplicité des aliances théoriques et artistiques de Bene imposait la necessite d’interroger et de contaminer les propres modes de recherche et d’écrite, établissant une production par fragments et approximations dont le présent texte en est une tentative.This article presents one of the topics raised by the research in progress on the work of the Italian artist Carmelo Bene. The author resumes a relation already made at the beginning of the research between the Benean actorial machine and the Deleuzean-Guattarian war machine, adding elements from an approach of stuttering in Gilles Deleuze, as well as from materials and experiences collected in the field research developed in Italy and France along the last three years. The initial goal of the research was to study the concepts that Carmelo Bene created in scene, seeking a closeness to what was original in his work. From the observation of the multiplicity of Bene’s theoretical and artistic alliances, it became necessary to interrogate and contaminate the research and writing modes themselves, establishing a production by means of fragments and closeness, being this text one of them
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