Characterization of the response of spring-based relative gravimeters during paroxysmal eruptions at Etna volcano

Gravity time sequences collected at Etna volcano by continuously recording spring-based relative gravimeters showed significant variations in temporal correspondence with paroxysmal eruptions. Since the observed gravity variations can only be partially related to subsurface mass redistribution phenomena, we investigated the instrumental effects due to ground vibrations such as those that accompany explosive activity. We simulated the performances of relative gravimeters with laboratory experiments to estimate their response to vertical and horizontal excitations. Laboratory tests were carried out using a vibrating platform capable of accelerating the instruments with intensities and frequencies, in both the vertical and horizontal directions, observed in the ground vibrations associated with paroxysmal events. The seismic signals recorded at Etna volcano during the 10 April 2011 lava fountain were analyzed to retrieve the parameters used to drive the vibration platform. We tested two gravimeters used for Etna volcano monitoring: the LaCoste & Romberg D#185 (Lafayette, CO, USA) and the Scintrex CG-3 M#9310234 (Concord, ON, Canada). The experiment results highlight that the vibrations resembling the seismic waves propagated during paroxysmal events cause an amplitude response in the gravity readings on the order of several hundred microgals (μGal). Generally, the relationship between the vibrations and the gravimeter response is nonlinear, with a fairly complex dependence on the frequencies and amplitudes of the signals acting on the gravimeters

Updates after the Near-Earth Commissioning Phase of Italian Spring Accelerometer – ISA

AbstractISA (Italian Spring Accelerometer) is a high sensitivity accelerometer flying, as scientific payload, on-board one of the two spacecraft (the Mercury Planetary Orbiter) of BepiColombo, the first ESA mission to Mercury. The first commissioning phase (performed in the period November 2018 - August 2019) allowed to verify the functionality of the instrument itself as well as of the related data handling and archiving system. Moreover, the acceleration measurements gathered in this time frame allow to envisage the potentiality of such an instrument as a high-accuracy monitor of the spacecraft mechanical environment

Gamma-Ray Burst observations by the high-energy charged particle detector on board the CSES-01 satellite between 2019 and 2021

In this paper we report the detection of five strong Gamma-Ray Bursts (GRBs) by the High-Energy Particle Detector (HEPD-01) mounted on board the China Seismo-Electromagnetic Satellite (CSES-01), operational since 2018 on a Sun-synchronous polar orbit at a $\sim$ 507 km altitude and 97$^\circ$ inclination. HEPD-01 was designed to detect high-energy electrons in the energy range 3 - 100 MeV, protons in the range 30 - 300 MeV, and light nuclei in the range 30 - 300 MeV/n. Nonetheless, Monte Carlo simulations have shown HEPD-01 is sensitive to gamma-ray photons in the energy range 300 keV - 50 MeV, even if with a moderate effective area above $\sim$ 5 MeV. A dedicated time correlation analysis between GRBs reported in literature and signals from a set of HEPD-01 trigger configuration masks has confirmed the anticipated detector sensitivity to high-energy photons. A comparison between the simultaneous time profiles of HEPD-01 electron fluxes and photons from GRB190114C, GRB190305A, GRB190928A, GRB200826B and GRB211211A has shown a remarkable similarity, in spite of the different energy ranges. The high-energy response, with peak sensitivity at about 2 MeV, and moderate effective area of the detector in the actual flight configuration explain why these five GRBs, characterised by a fluence above $\sim$ 3 $\times$ 10$^{-5}$ erg cm$^{-2}$ in the energy interval 300 keV - 50 MeV, have been detected.Comment: Accepted for publication in The Astrophysical Journal (ApJ

Orbital Frontalisation and Morphological Cranial Variability in Anthropoidea

The evolution of a developed visual system in primates is the result of an integration between physiological and morphological adaptations, involving different structures and tissues. In this context, cranial variability in Platyrrhini and Catarrhini has been analysed through a multivariate approach to landmark coordinates by mean of geometric morphometric tools. The main differences are related to a lateral expansion of the skull, sagittal decreasing and separation of medial structures (nasion, glabella), enlarging of inter-orbital distances. This component is markedly size-related, and it separates Hominoidea from the other Anthropoidea. This morphological shifting leads to an increasing distance between optic foramina, with consequent alignment of the visual axes. A second pattern separates Platyrrhini from Catarrhini, in particular from Cercopithecoidea. The South American primates are characterised by a decreasing of transversal diameters and orbital lateral shifting, with consequent divergence of the visual axes. Platyrrhini then show a minimum orbital convergence due to both these components, while 'Pongo pygmaeus' stands at the positive pole of these two frontalisation vectors. In Cercopithecoidea, the genus 'Papio' seems the more homogeneous and frontalised. 'Alouatta' spp., due to the extreme ayrorhinchy, stands phenetically related to Platyrrhini but showing an unique independent pattern

Orbital Frontation and Morphological Variability in Primates: Geometric Morphometric Analysis of the Upper Facial Structures in Anthropoidea

The anatomical and physiological adaptations characterising visual capabilities of primates are considered principal variables in the evolutionary radiation of the whole order. Orbital frontation is related to the reduction of the splanchnocranium and to stereoscopy, and affects overall skull architecture. Within this context, morphological variability in the orbital region of Anthropoidea has been analysed by means of multivariate techniques and spatial coordinates (geometric morphometrics) on a sample of 87 individuals. A Principal Components Analysis reveals a 'planar' morphospace, in which the first two components equally account for morphological variability. The first component explains a morpho-structural process of frontation, with posterior cranial widening, midsagittal reduction of the upper facial structures, and divergence of the optic foramina. This component is, as always, strongly size-related, depending in particular upon orbital height and neurocranial width. All Hominoidea are large animals and, therefore, particularly frontated, with 'Hylobates' and 'Pongo' showing greater frontation than expected from orbital dimensions. Ceboidea and Cercopithecoidea overlap entirely, except for 'Leontopithecus', which shows marked lateralisation because of its small size. The second component reflects a process related to orbital verticalisation, through posterior cranial widening, nasal and interorbital reduction, lengthening and slight convergence of the orbital axes, inferior orbital shift in a caudad direction, and glabellar protrusion. Cercopithecinae and Papioninae are the most verticalised taxa, in contrast with all Ceboidea and in particular 'Alouatta', because of its strong airorynchy. Also in 'Pongo', airorynchy leads to low verticalisation. The second principal component is related to the verticalisation index and to interorbital width. Cercopithecoidea show inverse correlation between frontation and verticalisation, with Colobidae probably lying in the lower range of the low verticalisation/high frontation pattern. Platyrrhini show low values for both, and more heterogeneous phenotypic variability, most of all in such specialised taxa as 'Alouatta' (airorynchy), 'Aotus' (nocturnal) and 'Leontopithecus' (dwarfism)

A structural approach to cranial variation in the genus 'Alouatta' (Primates, Atelidae)

Howler monkeys (genus 'Alouatta') display a peculiar cranial architecture, characterized by a high degree of airorhynchy. This condition may be evolutionarily influenced by a largely folivory diet (with selective pressures on mandibular and splachnocranial dimensions), social structure (related to the development of vocal sacs), or by the interaction between these or other more subtle factors. In terms of functional craniology, airorhynchy may be related to structural changes associated with the morphology of the supraorbital anatomy, with the spatial relationships between face and cranial base, or with morphogenetic variations of the pteric area. However the evolutionary changes associated with the cranial organization in 'Alouatta' are still currently unknown. This study is aimed at investigating the variation and covariation patterns in howler monkeys, considering both interand intrageneric morphological differences. We also investigated the structural role of the pteric area within the cranial functional matrix, in order to test possible relationships between its variation and the degree of airorhynchy. To address these objectives we applied landmark-based analysis and multivariate statistics to a comparative dataset of atelid adult skulls. Our results suggest that the cranial architecture in howlers is influenced by an allometric vector, which associates higher degrees of airorhynchy with splachnocranial enlargement, basicranial lengthening and neurocranial flattening. On the other hand, the relationship between pterion and airorhynchy could not be confirmed. Either way some minor morphological differences were identified, suggesting that variations of the pteric area may be instead related with the relative development of the masticatory apparatus

Cranial Structure and Evolution in 'Alouatta': Temporal Fossa and Interorbital Morphology

The genus 'Alouatta' is characterised by a peculiar cranial morphology, in which the splancnocranium appears as sagittally rotated with respect to the neurocranial axis. This process is called 'airorhynchy' and distinguishes the genus 'Alouatta' from all the other atelids. Previous analyses suggested that airorhynchy in 'Alouatta' is associated with the relationship between basi-cranial flexion and neurocranial development. Within this process, changes at the temporal fossa may represent a major structural rearrangement. In this paper, the area of the pterion in 'Alouatta' is investigated through Procrustes superimposition and thin-plate spline. The anatomy of the interorbital area has also been examined and described, since it represents a further source of variation among the atelids. The structural role of the temporal fossa is evidenced, while the interorbital morphology supports some phylogenetic hypotheses. Results are discussed considering the debate on the phylogenetic position of 'Paralouatta varonai' from the Quaternary of Cuba

The Galileo satellites Doresa and Milena and their goals in the field of fundamental physics within the Galileo for science (G4S_2.0) project

The 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

The Galileo for science (G4S_2.0) project: fundamental physics experiments with the Galileo satellites Doresa and Milena

G4S_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