排序方式: 共有44条查询结果,搜索用时 109 毫秒
31.
Davide Loreggia Silvano Fineschi Gerardo Capobianco Alessandro Bemporad Marta Casti Federico Landini Gianalfredo Nicolini Luca Zangrilli Giuseppe Massone Vladimiro Noce Marco Romoli Luca Terenzi Gianluca Morgante Massimiliano Belluso Cedric Thizy Camille Galy Aline Hermans Pierre Franco Luciano Accatino 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(11):3793-3806
PROBA-3 is a space mission of the European Space Agency that will test, and validate metrology and control systems for autonomous formation flying of two independent satellites. PROBA-3 will operate in a High Elliptic Orbit and when approaching the apogee at 6·104 Km, the two spacecraft will align to realize a giant externally occulted coronagraph named ASPIICS, with the telescope on one satellite and the external occulter on the other one, at inter-satellite distance of 144.3 m. The formation will be maintained over 6 hrs across the apogee transit and during this time different validation operations will be performed to confirm the effectiveness of the formation flying metrology concept, the metrology control systems and algorithms, and the spacecraft manoeuvring. The observation of the Sun’s Corona in the field of view [1.08;3.0]RSun will represent the scientific tool to confirm the formation flying alignment. In this paper, we review the mission concept and we describe the Shadow Position Sensors (SPS), one of the metrological systems designed to provide high accuracy (sub-millimetre level) absolute and relative alignment measurement of the formation flying. The metrology algorithm developed to convert the SPS measurements in lateral and longitudinal movement estimation is also described and the measurement budget summarized. 相似文献
32.
Mehdi Akhoondzadeh Angelo De Santis Dedalo Marchetti Alessandro Piscini Gianfranco Cianchini 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(1):248-263
After DEMETER satellite mission (2004–2010), the launch of the Swarm satellites (Alpha (A), Bravo (B) and Charlie (C)) has created a new opportunity in the study of earthquake ionospheric precursors. Nowadays, there is no doubt that multi precursors analysis is a necessary phase to better understand the LAIC (Lithosphere Atmosphere Ionosphere Coupling) mechanism before large earthquakes. In this study, using absolute scalar magnetometer, vector field magnetometer and electric field instrument on board Swarm satellites, GPS (Global Positioning System) measurements, MODIS-Aqua satellite and ECMWF (European Centre for Medium-Range Weather Forecasts) data, the variations of the electron density and temperature, magnetic field, TEC (Total Electron Content), LST (Land Surface Temperature), AOD (Aerosol Optical Depth) and SKT (SKin Temperature) have been surveyed to find the potential seismic anomalies around the strong Ecuador (Mw = 7.8) earthquake of 16 April 2016. The four solar and geomagnetic indices: F10.7, Dst, Kp and ap were investigated to distinguish whether the preliminary detected anomalies might be associated with the solar-geomagnetic activities instead of the seismo-ionospheric anomalies. The Swarm satellites (A, B and C) data analysis indicate the anomalies in time series of electron density variations on 7, 11 and 12 days before the event; the unusual variations in time series of electron temperature on 8 days preceding the earthquake; the analysis of the magnetic field scalar and vectors data show the considerable anomalies 52, 48, 23, 16, 11, 9 and 7 days before the main shock. A striking anomaly is detected in TEC variations on 1 day before earthquake at 9:00 UTC. The analysis of MODIS-Aqua night-time images shows that LST increase unusually on 11 days prior to main shock. In addition, the AOD variations obtained from MODIS measurements reach the maximum value on 10 days before the earthquake. The SKT around epicentral region presents anomalous higher value about 40 days before the earthquake. It should be noted that the different lead times of the observed anomalies could be acknowledged based on a reasonable LAIC earthquake mechanism. Our results emphasize that the Swarm satellites measurements play an undeniable role in progress the studies of the ionospheric precursors. 相似文献
33.
Carlo Scotto Alessandro Settimi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
The results of this paper demonstrate that the effect of collisions on the group refraction index is small, when the ordinary ray is considered. If, however, in order to improve the performance of a system for automatic interpretation of ionograms, the information contained in ordinary and extraordinary traces is combined, the effect of collisions between the electrons and neutral molecules should be taken into account for the extraordinary ray. The magnitude of these differences is generally very small and must be compared with the resolution in the virtual vertical height of the ionosonde, resolution which is typically of the order of few kilometers. 相似文献
34.
Florent Deleflie Alessandro Rossi Christophe Portmann Gilles Métris François Barlier 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
This paper aims at investigating the stability over 150 years of a very large number of trajectories in the Medium Earth Orbit (MEO) region, near the orbits devoted to radionavigation such as the Global Navigation Satellite Systems (GNSS like GPS, Glonass, Galileo, COMPASS). 相似文献
35.
Rosemary Killen Gabrielle Cremonese Helmut Lammer Stefano Orsini Andrew E. Potter Ann L. Sprague Peter Wurz Maxim L. Khodachenko Herbert I. M. Lichtenegger Anna Milillo Alessandro Mura 《Space Science Reviews》2007,132(2-4):433-509
It has been speculated that the composition of the exosphere is related to the composition of Mercury’s crustal materials.
If this relationship is true, then inferences regarding the bulk chemistry of the planet might be made from a thorough exospheric
study. The most vexing of all unsolved problems is the uncertainty in the source of each component. Historically, it has been
believed that H and He come primarily from the solar wind (Goldstein, B.E., et al. in J. Geophys. Res. 86:5485–5499, 1981), Na and K come from volatilized materials partitioned between Mercury’s crust and meteoritic impactors (Hunten, D.M., et
al. in Mercury, pp. 562–612, 1988; Morgan, T.H., et al. in Icarus 74:156–170, 1988; Killen, R.M., et al. in Icarus 171:1–19, 2004b). The processes that eject atoms and molecules into the exosphere of Mercury are generally considered to be thermal vaporization,
photon-stimulated desorption (PSD), impact vaporization, and ion sputtering. Each of these processes has its own temporal
and spatial dependence. The exosphere is strongly influenced by Mercury’s highly elliptical orbit and rapid orbital speed.
As a consequence the surface undergoes large fluctuations in temperature and experiences differences of insolation with longitude.
Because there is no inclination of the orbital axis, there are regions at extreme northern and southern latitudes that are
never exposed to direct sunlight. These cold regions may serve as traps for exospheric constituents or for material that is
brought in by exogenic sources such as comets, interplanetary dust, or solar wind, etc. The source rates are dependent not
only on temperature and composition of the surface, but also on such factors as porosity, mineralogy, and space weathering.
They are not independent of each other. For instance, ion impact may create crystal defects which enhance diffusion of atoms
through the grain, and in turn enhance the efficiency of PSD. The impact flux and the size distribution of impactors affects
regolith turnover rates (gardening) and the depth dependence of vaporization rates. Gardening serves both as a sink for material
and as a source for fresh material. This is extremely important in bounding the rates of the other processes. Space weathering
effects, such as the creation of needle-like structures in the regolith, will limit the ejection of atoms by such processes
as PSD and ion-sputtering. Therefore, the use of laboratory rates in estimates of exospheric source rates can be helpful but
also are often inaccurate if not modified appropriately. Porosity effects may reduce yields by a factor of three (Cassidy,
T.A., and Johnson, R.E. in Icarus 176:499–507, 2005). The loss of all atomic species from Mercury’s exosphere other than H and He must be by non-thermal escape. The relative
rates of photo-ionization, loss of photo-ions to the solar wind, entrainment of ions in the magnetosphere and direct impact
of photo-ions to the surface are an area of active research. These source and loss processes will be discussed in this chapter. 相似文献
36.
Christina Plainaki Tim A. Cassidy Valery I. Shematovich Anna Milillo Peter Wurz Audrey Vorburger Lorenz Roth André Galli Martin Rubin Aljona Blöcker Pontus C. Brandt Frank Crary Iannis Dandouras Xianzhe Jia Davide Grassi Paul Hartogh Alice Lucchetti Melissa McGrath Valeria Mangano Alessandro Mura Stefano Orsini Chris Paranicas Aikaterini Radioti Kurt D. Retherford Joachim Saur Ben Teolis 《Space Science Reviews》2018,214(1):40
Despite the numerous modeling efforts of the past, our knowledge on the radiation-induced physical and chemical processes in Europa’s tenuous atmosphere and on the exchange of material between the moon’s surface and Jupiter’s magnetosphere remains limited. In lack of an adequate number of in situ observations, the existence of a wide variety of models based on different scenarios and considerations has resulted in a fragmentary understanding of the interactions of the magnetospheric ion population with both the moon’s icy surface and neutral gas envelope. Models show large discrepancy in the source and loss rates of the different constituents as well as in the determination of the spatial distribution of the atmosphere and its variation with time. The existence of several models based on very different approaches highlights the need of a detailed comparison among them with the final goal of developing a unified model of Europa’s tenuous atmosphere. The availability to the science community of such a model could be of particular interest in view of the planning of the future mission observations (e.g., ESA’s JUpiter ICy moons Explorer (JUICE) mission, and NASA’s Europa Clipper mission). We review the existing models of Europa’s tenuous atmosphere and discuss each of their derived characteristics of the neutral environment. We also discuss discrepancies among different models and the assumptions of the plasma environment in the vicinity of Europa. A summary of the existing observations of both the neutral and the plasma environments at Europa is also presented. The characteristics of a global unified model of the tenuous atmosphere are, then, discussed. Finally, we identify needed future experimental work in laboratories and propose some suitable observation strategies for upcoming missions. 相似文献
37.
Cinzia Giacomuzzo Alessandro Francesconi Luciano Anselmo 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
This paper presents a case study of Micrometeoroids and Orbital Debris risk assessment for a spacecraft flying in an orbit close to that of the Italian Cosmo-Skymed constellation. The aim of the analysis was to calculate the failure flux impinging on the satellite external shell, taking into account both geometry and materials of satellite surfaces. Furthermore the analysis included the evaluation of the contribution to debris population at the selected orbit of the fragments produced by a Chinese Anti-SATellite experiment, which caused the catastrophic break-up of the satellite Fengyun 1C in January 2007. 相似文献
38.
Alessandro Settimi Marco Pietrella Michael Pezzopane Bruno Zolesi Cesidio Bianchi Carlo Scotto 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
The present paper proposes to discuss the ionospheric absorption, assuming a quasi-flat layered ionospheric medium, with small horizontal gradients. A recent complex eikonal model (Settimi et al., 2013b) is applied, useful to calculate the absorption due to the ionospheric D-layer, which can be approximately characterized by a linearized analytical profile of complex refractive index, covering a short range of heights between h1 = 50 km and h2 = 90 km. Moreover, Settimi et al. (2013c) have already compared the complex eikonal model for the D-layer with the analytical Chapman’s profile of ionospheric electron density; the corresponding absorption coefficient is more accurate than Rawer’s theory (1976) in the range of middle critical frequencies. Finally, in this paper, the simple complex eikonal equations, in quasi-longitudinal (QL) approximation, for calculating the non-deviative absorption coefficient due to the propagation across the D-layer are encoded into a so called COMPLEIK (COMPLex EIKonal) subroutine of the IONORT (IONOspheric Ray-Tracing) program ( Azzarone et al., 2012). The IONORT program, which simulates the three-dimensional (3-D) ray-tracing for high frequencies (HF) waves in the ionosphere, runs on the assimilative ISP (IRI-SIRMUP-P) discrete model over the Mediterranean area ( Pezzopane et al., 2011). As main outcome of the paper, the simple COMPLEIK algorithm is compared to the more elaborate semi-empirical ICEPAC formula (Stewart, undated), which refers to various phenomenological parameters such as the critical frequency of E-layer. COMPLEIK is reliable just like the ICEPAC, with the advantage of being implemented more directly. Indeed, the complex eikonal model depends just on some parameters of the electron density profile, which are numerically calculable, such as the maximum height. 相似文献
39.
Vladimiro Noce Davide Loreggia Gerardo Capobianco Silvano Fineschi Alessandro Bemporad Marta Casti Steven Buckley Marco Romoli Mauro Focardi Massimiliano Belluso Cédric Thizy Aline Hermans Damien Galano Jorg Versluys 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(11):3807-3818
PROBA-3 is an ESA mission aimed at the demonstration of formation flying performance of two satellites that will form a giant coronagraph in space. The first spacecraft will host a telescope imaging the solar corona in visible light, while the second, the external occulter, will produce an artificial eclipse. This instrument is named ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun). To accomplish the payload's scientific tasks, PROBA-3 will ensure sub-millimeter reciprocal positioning of its two satellites using closed-loop on-board metrology. Several metrology systems will be used and the Shadow Position Sensor (SPS) subsystem senses the penumbra around the instrument aperture and returns the 3-D displacement of the coronagraph satellite, with respect to its nominal position, by running a dedicated algorithm. In this paper, we describe how the SPS works and the choices made to accomplish the mission objectives. 相似文献
40.
Carlo Scotto Alessandro Ippolito Dario Sabbagh 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(1):337-342
A method is presented for automatic detection of spread-F. The method is based on an image recognition technique and is applied to ionograms recorded at the ionospheric station of Tucumán (26.9°S, 294.6°E). The performance achieved is statistically evaluated and demonstrated with significant examples. The proposed method improves Autoscala's ability to reject ionograms with insufficient information, including those featuring Spread-F. Automatic identification of cases of spread-F is of additional interest in Space Weather applications, when it helps detect degraded radio propagation conditions.The present data analysis is a retrospective study but forms the basis for real-time application as an extension of Autoscala’s capabilities. 相似文献