The 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.
First detection of Non-Gravitational accelerations at Mercury / DE FILIPPIS, Umberto; Lefevre, Carlo; Magnafico, Carmelo; Lucente, Marco; Lucchesi, David; Peron, Roberto; Santoli, Francesco. - (2022). (Intervento presentato al convegno AGU Fall Meeting 2022 tenutosi a Chicago).
First detection of Non-Gravitational accelerations at Mercury
Umberto De FilippisPrimo
;Marco Lucente;
2022
Abstract
The 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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.