Combined MTL-fullwave statistical approach for fast estimation of radiated immunity of spacecraft cable assemblies involving multipair bundles

In this work, a computationally-efficient modelling approach is developed to predict the electromagnetic noise induced in the terminal units of random bundles of twisted-wire pairs mounted onboard spacecraft. The proposed model combines the results of a preliminary full wave simulation, aimed at evaluating the electromagnetic field inside the space vehicle’s metallic body, with a stochastic model of a random bundle, based on multiconductor transmission line (MTL) theory. Model assessment versus measurement data obtained characterizing real wiring harness in a full-scale satellite mock-up demonstrates the large sensitivity (up to 40 decibels) of the induced noise levels to different bundle configurations, and corroborates the effectiveness of the proposed simplified modelling strategy for estimating the modal noise voltages induced in the terminal units

Experimental measurement of the response of a twisted-wire pair exposed to a plane-wave field

reserved3A recent work has presented closed-form expressions for the response of a twisted-wire pair (TWP) above ground illuminated by an external plane wave. This work addresses the same topic from an experimental point of view. The proposed setup consists of a TWP terminated with passive networks equipped with radio-frequency detectors. The measurement procedure and its relevant technical issues are discussed. In particular, the following main aspects are covered: (a) generation of a controlled plane-wave electromagnetic field; (b) characterization of the non-ideal behavior of the TWP terminal networks; (c) need to develop a strategy to separate the common-mode (CM) from the differential-mode (DM) induced voltage, (d) sensitivity of the results to unknown/uncontrolled setup parameters. Measurements are compared with the outcome of the aforementioned radiated susceptibility (RS) model with the objective to ascertain model accuracy and to obtain physical insight in the field-to-wire coupling phenomenon.Giordano Spadacini; Sergio A. Pignari; Filippo MarlianiSpadacini, Giordano; Pignari, SERGIO AMEDEO; Filippo, Marlian

Particle swarm optimization for multiple dipole modeling of space equipment

An advanced modeling algorithm based on particle swarm optimization (PSO) has been developed to solve multiple dipole modeling (MDM) problems in space applications. MDM is a method to represent spacecraft units as a set of equivalent magnetic dipoles able to reconstruct, in the far-field distance, the same magnetostatic field. This procedure allows preparing a magnetic model of the spacecraft during design and development phases. Moreover, it allows refined prediction of magnetic cleanliness for space missions with equipment susceptible to magnetic fields. Indeed, owing to the increase of missions requiring magnetostatic cleanliness, such characterization becomes increasingly important. To validate the PSO procedure, synthetic data have been initially used, generated using a software simulator. Algorithm performance has been tested through measured data acquired using the Mobile Coil Facility located at the European Space Research and Technology Centre in The Netherlands. Starting from measured data, the algorithm iteratively identifies the values of the unknowns, positions, and magnetic moments of the equivalent dipoles that best match the measured field. Since the problem is ill posed, several solutions are possible. To develop a reliable algorithm, some test cases have been analyzed where the expected solution is known. This allowed improving the algorithm leading to satisfying results

Frequency-response variability of voltages induced by field-to-wire coupling in random bundles of twisted-wire pairs on-board small satellites

Procedures and results are reported for an experiment aimed at assessing noise induced by field coupling to a random bundle of twisted-wire pairs (TWPs) installed in a complex electromagnetic environment. The test case is representative of radiated-susceptibility phenomena occurring in aerospace systems such as satellite for scientific missions. In particular, the structure under analysis is composed of six randomly-bundled TWPs, excited by a nonuniform electromagnetic field generated by a monopole antenna inside the mock-up of a small-sized satellite, in the frequency range 250 MHz – 1 GHz. Measurement is repeated for several hand-made samples of the bundle. It is shown that the common-mode and differential-mode voltages induced in terminal loads are characterized by high sensitivity (up to 40 dBs) to different bundle samples. By the light of experimental results, the weakness of deterministic and simplified field-to-wire coupling models is discussed

Prediction of Conducted Emissions in Satellite Power Buses

This work reports a modeling methodology for the prediction of conducted emissions (CE) in a wide frequency range (up to 100 MHz), which are generated by dc/dc converters and propagate along the power buses of satellites. In particular, the dc/dc converter seen as a source of CE is represented by a behavioral model, whose parameters can be identified by two unit-level experimental procedures performed in controlled test setups. A simplified multiconductor transmission-line (MTL) model is developed to account for the propagation of CE in shielded bundles of twisted-wire pairs used as power cables. The whole power system is represented by the interconnection of the circuit models of dc/dc converters, cables, and Power Conditioning and Distribution Unit (PCDU). By solving the obtained network, frequency spectra of CE can be predicted. Experimental results are reported to substantiate the accuracy of the proposed unit-level dc/dc converter model and the MTL model of cables. Finally, a system-level test setup composed of three dc/dc converters connected to a PCDU is considered, and predicted CE are compared versus experimental measurements

PLATO: the ESA mission for exo-planets discovery

PLATO (PLAnetary Transits and Oscillation of stars) is the ESA Medium size dedicated to exo-planets discovery, adopted in the framework of the Cosmic Vision program. The PLATO launch is planned in 2026 and the mission will last at least 4 years in the Lagrangian point L2. The primary scientific goal of PLATO is to discover and characterize a large amount of exo-planets hosted by bright nearby stars, constraining with unprecedented precision their radii by mean of transits technique and the age of the stars through by asteroseismology. By coupling the radius information with the mass knowledge, provided by a dedicated ground-based spectroscopy radial velocity measurements campaign, it would be possible to determine the planet density. Ultimately, PLATO will deliver the largest samples ever of well characterized exo-planets, discriminating among their ‘zoology’. The large amount of required b right stars can be achieved by a relatively small aperture telescope (about 1 meter class) with a wide Field of View (about 1000 square degrees). The PLATO strategy is to split the collecting area into 24 identical 120 mm aperture diameter fully refractive cameras with partially overlapped Field of View delivering an overall instantaneous sky covered area of about 2232square degrees. The opto-mechanical sub-system of each camera, namely Telescope Optical Unit, is basically composed by a 6 lenses fully refractive optical system, presenting one aspheric surface on the front lens, and by a mechanical structure made in AlBeMet

Metis: the Solar Orbiter visible light and ultraviolet coronal imager

Aims. Metis is the first solar coronagraph designed for a space mission and is capable of performing simultaneous imaging of the off-limb solar corona in both visible and UV light. The observations obtained with Metis aboard the Solar Orbiter ESA-NASA observatory will enable us to diagnose, with unprecedented temporal coverage and spatial resolution, the structures and dynamics of the full corona in a square field of view (FoV) of ±2.9° in width, with an inner circular FoV at 1.6°, thus spanning the solar atmosphere from 1.7 R⊙ to about 9 R⊙, owing to the eccentricity of the spacecraft orbit. Due to the uniqueness of the Solar Orbiter mission profile, Metis will be able to observe the solar corona from a close (0.28 AU, at the closest perihelion) vantage point, achieving increasing out-of-ecliptic views with the increase of the orbit inclination over time. Moreover, observations near perihelion, during the phase of lower rotational velocity of the solar surface relative to the spacecraft, allow longer-term studies of the off-limb coronal features, thus finally disentangling their intrinsic evolution from effects due to solar rotation. Methods. Thanks to a novel occultation design and a combination of a UV interference coating of the mirrors and a spectral bandpass filter, Metis images the solar corona simultaneously in the visible light band, between 580 and 640 nm, and in the UV H 

The PLATO Mission

International audiencePLATO (PLAnetary Transits and Oscillations of stars) is ESA's M3 mission designed to detect and characterise extrasolar planets and perform asteroseismic monitoring of a large number of stars. PLATO will detect small planets (down to <2 R_(Earth)) around bright stars (<11 mag), including terrestrial planets in the habitable zone of solar-like stars. With the complement of radial velocity observations from the ground, planets will be characterised for their radius, mass, and age with high accuracy (5 %, 10 %, 10 % for an Earth-Sun combination respectively). PLATO will provide us with a large-scale catalogue of well-characterised small planets up to intermediate orbital periods, relevant for a meaningful comparison to planet formation theories and to better understand planet evolution. It will make possible comparative exoplanetology to place our Solar System planets in a broader context. In parallel, PLATO will study (host) stars using asteroseismology, allowing us to determine the stellar properties with high accuracy, substantially enhancing our knowledge of stellar structure and evolution. The payload instrument consists of 26 cameras with 12cm aperture each. For at least four years, the mission will perform high-precision photometric measurements. Here we review the science objectives, present PLATO's target samples and fields, provide an overview of expected core science performance as well as a description of the instrument and the mission profile at the beginning of the serial production of the flight cameras. PLATO is scheduled for a launch date end 2026. This overview therefore provides a summary of the mission to the community in preparation of the upcoming operational phases

The PLATO Mission

International audiencePLATO (PLAnetary Transits and Oscillations of stars) is ESA's M3 mission designed to detect and characterise extrasolar planets and perform asteroseismic monitoring of a large number of stars. PLATO will detect small planets (down to <2 R_(Earth)) around bright stars (<11 mag), including terrestrial planets in the habitable zone of solar-like stars. With the complement of radial velocity observations from the ground, planets will be characterised for their radius, mass, and age with high accuracy (5 %, 10 %, 10 % for an Earth-Sun combination respectively). PLATO will provide us with a large-scale catalogue of well-characterised small planets up to intermediate orbital periods, relevant for a meaningful comparison to planet formation theories and to better understand planet evolution. It will make possible comparative exoplanetology to place our Solar System planets in a broader context. In parallel, PLATO will study (host) stars using asteroseismology, allowing us to determine the stellar properties with high accuracy, substantially enhancing our knowledge of stellar structure and evolution. The payload instrument consists of 26 cameras with 12cm aperture each. For at least four years, the mission will perform high-precision photometric measurements. Here we review the science objectives, present PLATO's target samples and fields, provide an overview of expected core science performance as well as a description of the instrument and the mission profile at the beginning of the serial production of the flight cameras. PLATO is scheduled for a launch date end 2026. This overview therefore provides a summary of the mission to the community in preparation of the upcoming operational phases