Satellite X-band SAR data exploitation trends in the framework of ASI's COSMO-SkyMed Open Call initiative

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Libration Damping System in the Attitude Stabilization of University Microsatellites

In the last twenty years a large impulse in the production of micro and nanosatellites has been recorded all over the world. A number of space university programs started in different countries with the aim to provide students with hands-on training in the field of space technologies. In this field the Gruppo di Astrodinamica dell’Università degli Studi di Roma “La Sapienza” (GAUSS), has been working for more than 15 years with the UNISAT program. Currently, three new educational projects are under development: Unisat-5, EduSAT and UNICubeSAT. Both UNISAT-5 and EduSAT satellites use passive attitude stabilization systems, which permit to keep costs low and to get adequate system reliability. In the paper an overview of EduSAT and UNISAT-5 attitude stabilization systems and an analysis of the main issues related to these topics are given. Moreover the paper deals with the design and sizing of a libration damping system in the attitude stabilization of EduSAT, stabilized by a passive magnetic system, and UNISAT-5, stabilized by a gravity gradient boom. Finally, results of numerical simulations are sketched. Keywords: Satellite, attitude stabilization, gravitational stabilization, magnetic stabilization, magnetic damping, hysteresis rod

Triple Probe System For In Situ Ionospheric Plasma Monitoring

The capability to establish the magnitudo, time and place of a forthcoming earthquake is still far from having a reliable and accurate prevision of practical interest. Different precursory phenomena of forthcoming earthquakes have been experimentally observed; they are mostly linked to a microfracturation of the rock due to stress accumulation during the pre-seismic phase in the hypocentral zone of an earthquake. The microcracks in the rocks can be considered seismic sources able to generate electromagnetic emissions, in particular in ULF-ELF bands (0-3000 Hz). The electromagnetic waves spread through the lithosphere to the ionosphere and the magnetosphere and they produce irregularities (Earth magnetic field variations, ionospheric plasma parameters disturbances and particles precipitation from Van Allen belts). In addition, the shallow earthquakes are capable to produce gravity oscillations, propagating upwards and coupling with neutral atmosphere and, eventually, with ionospheric layers. Significant variations of the total electron content in the ionosphere have been measured through GPS receivers. A space mission seems to be an affordable way to achieve in-situ observations, overall the Earth. A plasma diagnostic system suitable to be hosted on board LEO satellites to investigate the presence of ionosphere disturbances has been designed, manufactured and tested. The system is an electrostatic probe, specifically a Triple Probe System (TPS), which allows the local plasma density and electron temperature determination through acquisition of instantaneous voltage and current measurements. A prototype has been arranged to be hosted on board UNISAT-4, a low-cost university satellite built by GAUSS (Gruppo di Astrodinamica \u2013 Universit\ue0 degli Studi di Roma \u201cLa Sapienza\u201d), scheduled to be launched on December 2005. The paper deals with the TPS basic concepts and some preliminary results, obtained in a test campaign carried out in a climatic room from -40\ub0C to +60\ub0C, are depicted

HypSat program

Since many years the Group of Astrodynamics of University of Rome "La Sapienza" (GAUSS) established a fruitful collaboration with Keldysh Institute for Applied Mathematics of Russian Academy of Sciences in Moscow. The GAUSS established the UNISAT program achieving experience in design, manufacturing and operating in orbit microsatellites. This program starts in early nineties at School of Aerospace Engineering with the aim to design, realize and launch small educational satellites involving students, researchers and professor in a real space project. All the satellites were realized with terrestrial off-the-shelf components in order to keep low the costs and make them affordable for university budgets. In the framework of this program three satellites have already been launched (respectively in 2000, 2002 and 2004) from Baykonour Cosmodrome with DNEPR launch vehicle and a fourth satellite is ready to be launched. On the other hand the Keldysh Institute of Applied Mathematics with the industry achieved good experience in Hyperspectometer design and realization. Different experiences and knowledge found a common project in HypSat. HypSat is a project, supported from FILAS (Finanziaria laziale di sviluppo of the Lazio region), to design a microsatellite capable to monitoring natural disasters, (fires, Earthquakes,..). The HypSat bus will be designed and manufactured from GAUSS on the basis of its past experiences and it will board, as primary payload, an enhanced version of Hyperspectrometer developed by the Keldysh Institute of Applied Mathematics of RAS. The paper deals with the HypSat main subsystems design. Moreover a coverage analysis for Lazio region has been carried out and results are discussed, taking into account the effectiveness of expected access time with respect to different natural calamities and considering the possibility to use a constellation of satellites to reduce the gap time. The Hyperspectrometer is also deeply depicted giving relevance to its main capabilities and constraints and evaluating expected results in Earth disasters monitoring