Innovative Configuration for a Far Infrared Space Interferometer

In the last ten years many proposals and studies have been advanced for a far-IR kilometer baseline interferometer. This paper shows the results of FISICA (Far Infrared Space Interferometer Critical Assessment), an FP7 program of the European Community. In particular, we focus on an innovative strategy to cover the plane of observation with a minimal propellant consumption. Results of some numerical simulations, carried out for a three-booms configuration, are provided

Measurement of the quality factor of a new low-frequency differential accelerometer for testing the equivalence principle

A cryogenic differential accelerometer has been developed to test the weak equivalence principle to a few parts in 1015 within the framework of the general relativity accuracy test in an Einstein elevator experiment. The prototype sensor was designed to identify, address, and solve the major issues associated with various aspects of the experiment. This paper illustrates the measurements conducted on this prototype sensor to attain a high quality factor (Q ∼ 105) at low frequencies (<20 Hz). Such a value is necessary for reducing the Brownian noise to match the target acceleration noise of 10−14 g/√Hz, hence providing the desired experimental accuracy.AstronomyPhysic

Equivalence Principle's Test with Improved Accuracy using a Cryogenic Differential Accelerometer Installed on a Pendulum.

We present here a concept for a new experimental test of the Weak Equivalence Principle (WEP) carried out in the gravity field of the Sun. Two test masses of different materials are the central elements of a differential accelerometer with zero baseline. The differential accelerometer is placed on a pendulum, in such a way as to make the common center of mass coincident with the center of mass of the pendulum. Ensuring a very precise centering, such a system should provide a high degree of attenuation of the local seismic noise, which together with an integration time of the order of tens of days would allow verification of the WEP with an accuracy improved by at least an order of magnitude with respect to the state of the art. One of the strengths of this experiment is the know-how acquired from a previous study and technology development (GREAT: General Relativity Accuracy Test) that involved a test of the WEP in the gravity field of the Earth, in free fall inside a co-moving capsule released from a stratospheric balloon. The description of the experiment will be followed by a critical analysis of the challenges associated with its implementation.Astronom

The CAESAR project for the ASI space weather infrastructure

This paper presents the project Comprehensive spAce wEather Studies for the ASPIS prototype Realization (CAESAR), which aims to tackle the relevant aspects of Space Weather (SWE) science and develop a prototype of the scientific data centre for Space Weather of the Italian Space Agency (ASI) called ASPIS (ASI SPace Weather InfraStructure). To this end, CAESAR involves the majority of the SWE Italian community, bringing together 10 Italian institutions as partners, and a total of 92 researchers. The CAESAR approach encompasses the whole chain of phenomena from the Sun to Earth up to planetary environments in a multidisciplinary, comprehensive, and unprecedented way. Detailed and integrated studies are being performed on a number of well-observed “target SWE events”, which exhibit noticeable SWE characteristics from several SWE perspectives. CAESAR investigations synergistically exploit a great variety of different products (datasets, codes, models), both long-standing and novel, that will be made available in the ASPIS prototype: this will consist of a relational database (DB), an interface, and a wiki-like documentation structure. The DB will be accessed through both a Web graphical interface and the ASPIS.py module, i.e., a library of functions in Python, which will be available for download and installation. The ASPIS prototype will unify multiple SWE resources through a flexible and adaptable architecture, and will integrate currently available international SWE assets to foster scientific studies and advance forecasting capabilities

Strain sensing with CNT Nanocomposites: Static, cyclic and dynamic electromechanical material characterization

Carbon Nanotube (CNT) nanocomposites are one of the most important candidates to realize innovative strain sensors for Structural Health Monitoring (SHM) applications. In this work, the effect of static and dynamic strain on the electromechanical properties of carbon nanotubes (CNTs) nanocomposites, is investigated. In particular the nanocomposite is formed by multi-walled CNTs (MWNTs) embedded in a PolymethylMethacrylate (PMMA) matrix. The MWNTs randomly distributed within the PMMA matrix form conductive paths. These paths modify they morphology when the material is strained. Consequently the overall material conductivity changes. Continuous monitoring is possible by correlating these electrical changes to the deformation level of the material. Different specimens are made by varying the MWNTs content (3%, 5%, 7%, weight fractions) and are tested under varying static, cyclic and dynamic loading conditions. It is found that the Gauge Factor (GF) and nanocomposite sensitivity to strain, are directly related to the MWNTs content. Nanocomposites with higher MWNTs percentages (7%) show the best behaviour with a smaller dispersion of the experimental data. This data reproducibility is comparable to that of conventional strain gauges. The proposed functional material has the beauty of being ultralight and flexible. Moreover this material design has the potential of being scalable in size allowing continuous monitoring of larger structural areas than commercial sensors. The results shown in this paper highlight that this nanocomposite is a great candidate for the realization of advanced sensing devices

Sounding the atmospheric density at the altitude of LARES and Ajisai during solar cycle 24

During Solar Cycle 24, the passive spherical satellites LARES and Ajisai, placed in nearly circular orbits with mean geodetic altitudes between 1450 and 1500 km, were used as powerful tools to probe the neutral atmosphere density and the performances of six thermospheric models in orbital regimes for which the role of dominant atomic species is contended by hydrogen and helium, and accurate satellite measurements are scarce. The starting point of the analysis was the accurate determination of the secular semi-major axis decay rate and the corresponding neutral drag acceleration in a satellite- centered orbital system. Then, for each satellite, thermospheric model and solar activity level, the drag coefficients capable of reproducing the orbital decay observed were found. These coefficients were finally compared with the physical drag coefficients computed for both satellites in order to assess the biases affecting the thermospheric density models. None of them could be considered unconditionally the best; the specific outcome depending on solar activity and the regions of the atmosphere crossed by the satellites. During solar maximum conditions, an additional density bias linked to the satellite orbit inclination was detected

Measurements of general relativity precessions in the field of the Earth with laser-ranged satellites and the LARASE program

The LAser Ranged Satellites Experiment (LARASE) is a new experiment whose main purpose is to provide precise and accurate measurements of gravitation in the weak-field and slow- motion (WFSM) limit of Einstein’s theory of general relativity by means of a very precise laser tracking of geodetic satellites in orbit around the Earth. Beside the good quality of the tracking observations of the satellites orbit, guaranteed by the powerful Satellite Laser Ranging (SLR) technique of the International Laser Ranging Service (ILRS), also the quality of the dynamical models implemented in a software code plays a fundamental role in order to obtain precise and accurate measurements of relativistic physics. The models have to account for the per- turbations provoked by both gravitational and non-gravitational perturbations in such a way to reduce as well as possible the difference between the observed range, from the tracking, and the computed one, from the models. In particular, LARASE is an experiment that aims to improve the dynamical models of the present best laser-ranged satellites in order to perform a precise and accurate orbit determination. This represents a first step towards new refined tests and measurements of GR in the field of the Earth. After a brief presentation of the main relativistic measurements which constitute the main goals of LARASE, the results obtained during last year will be discussed in terms of the improvements reached in the satellites orbit modelling and in their precise orbit determination

The LARASE research program. State of the art on modelling and measurements of general relativity effects in the field of the Earth: A preliminary measurement of the Lense-Thirring effect

The LARASE research program is funded by the Italian National Institute for Nuclear Physics and it is a collab- oration between different institutions. LARASE aims to provide very precise and accurate measurements of the General Relativity effects that perturb, from the Newtonian point of view, the trajectory of a satellite orbiting the Earth. The improvements obtained by the LARASE collaboration with respect to the previous year are presented in terms of orbit modelling, precise orbit determination and a preliminary measurement of the Lense- Thirring precession. A preliminary and partial estimate of the corresponding error budget is given and it is discussed with the main difficulties present, and to overcome in order to provide a definitive, robust and reliable estimate of the main systematic sources of error