1,721,242 research outputs found
A geometric realization of
No full textSummary: Given an orientable weakly self-dual manifold of rank two (see the second author, Asian J. Math. 9, No. 1, 79--101 (2005; Zbl 1085.14035)), we build a geometric realization of the Lie algebra \germ{sl}(6,\Bbb C) as a naturally defined algebra of endomorphisms of the space of differential forms of . We provide an explicit description of Serre generators in terms of natural generators of . This construction gives a bundle on which is related to the search for a natural gauge theory on . We consider this paper as a first step in the study of a rich and interesting algebraic structure
Nanotechnology for University Nanosatellites Flying in Formation: Prototype Design and Test
No full textThe goal of the research program is to develop a prototype of a satellite constellation consisting of four Nanosatelites flying in a formation, having on board a stereoscopic imaging experiment for the analysis of the Earth surface. A camera is on-board each of the four nanosatellites, and images of the Earth are taken from all the satellites at the same time. A space debris mitigation experiment is also scheduled, de-orbiting the launch adapter by an inflatable balloon. Use of recently developed and not yet space flight tested nanotechnology devices is a key point of the research program, in order to save weight and volume for the system. Each University Institution participating in the Project develops its own nanosatellite, according to prefixed standards, including the mechanical, electrical, communications interfaces and the co-ordinated orbital control strategy for the formation maintenance. Exchange of information and know-how among all the participating Universities is also one on the project goals, based on the experience gained in previously financed programs, in which the same Universities have been involved in the development of a common project. The nanosatellites are launched together in a single launcher adapter. After the launch adapter separates from the launcher the nanosatellites are released from the adapter one at a time at regular time intervals. The adapter is also exploited to perform a space debris mitigation experiment. After the last nanosatellite has been released, an inflatable balloon installed on the adapter is inflated, de-orbiting the adapter. The adapter itself is an active satellite, equipped with a battery, and a telemetry system, downloading the balloon pressure measured on-board. The nanosatellites are 10cm to 15 cm cubes, weighting less than 5 kg. They are three axis stabilised and have a propulsion system for orbit and attitude control. Orbit determination and relative formation geometry measurements are achieved either using GPS receivers, or by cross radio links among the satellites. The formation control requirements and the relative geometry determination algorithm is agreed among all of the participants in the first three months of the program. Every satellite is equipped with at least two radio transmitters and two receivers in the UHF and VHF band. One of radio channel is devoted to communication with the ground station. The other is used for cross link among the satellites. This gives both exchange of information (commands, data...) and a measurement system for the relative geometry of the satellites. Terrestrial components adapted to be operated in the space environment will be used whenever possible, in order to keep the system cost down. Based on the UNISAT-1 and UNISAT-2 experience at Università di Roma “La Sapienza”, this proved to be an effective way to approach the problem of budget constraints, leading to systems capable of one year operation in orbit at reasonable cost. On the other hand, nanotechnology devices seem to be a key point for the research program feasibility, allowing to keep down weight, power and volume for on-board components, such as attitude sensors and propulsion system. Nanotechnology based sensors have been recently proposed, including magnetoresistive magnetometers, weighting few grams and few centimetres size, while nano-optical devices could be used to build sun sensors in a square centimetre surface. Propulsion systems based on “micronozzles”, giving 100 microNewton thrust have been recently developed and ground tested. These devices are going to be flown on UNISAT-2 next year. These could be a basis for future developments, including miniaturisation of the control valves, reducing the overall weight of the propulsion system to the gas and tank weight, with nozzle and valve built on a single silicon chip
Development and testing of technologies for autonomous navigation and control of formation flying nanosatellites
No full textProject objectives The proposed research is part of a national project (coordinated by the University of Rome) aimed at developing and in-flight testing innovative technologies for formation flying nanosatellites. The formation will be composed by three nanosatellites (a mother satellite and two smaller satellites) developed in cooperation by the three university teams. Project innovative aspects are: formation flying of satellites connected by tethers, formation flying of free-flying satellites with communication interlinks, in-flight testing of autonomous navigation and control systems and logics. In this context, the specific project of the research unit at the University of Naples "Federico II" deals with the development of advanced techniques and technologies for the autonomous navigation and control of the nanosatellites' formation. The research will take advantage of the team experience in microsatellite design and development and in space system guidance, navigation and control. In particular, innovative solutions will be investigated to develop an autonomous navigation and control system based on Differential GPS (DGPS) and sensor fusion technologies. Since the project focus is on distributed systems of nanosatellites, solutions will be analyzed based on the use of MEMS (Micro-Electro-Mechanical-System) and CMOS (Complementary MOS) technologies to develop compact sensors and actuators
Design and development of an autonomous navigation system of Unmanned Aerial Vehicles (UAV) for environment monitoring
No full textTHE USE OF UAVs (UNMANNED AERIAL VEHICLE), COMPACT PLANES WITHOUT CREW AND EQUIPPED WITH AUTONOMOUS SYSTEMS FOR NAVIGATION AND CONTROL, IS VERY INTERESTING FOR ENVIRONMENT MONITORING. UAVS CAN BE A VALID OPERATIONAL TOOL TO MONITOR REGIONAL AREAS, IN PARTICULAR WHEN IMMEDIATE ACTIONS ARE NEEDED BECAUSE OF NATURAL DISASTERS (FIRES, FLOODS, POLLUTION, ETC.), SINCE, IF PROPERLY EQUIPPED, THEY CAN SUPPLY DATA AND HIGH-RES IMAGES WITHOUT RISKS FOR OPERATORS THANK TO THE ABSENCE OF ON-BOARD PERSONNEL. IN ADDITION, AUTONOMOUS SYSTEMS ALLOW FOR REAL-TIME OPERATION BECAUSE THEY CAN BE ACTIVATED IN VERY SHORT TIME AND CONTROLLED BY PERSONNEL NON-SPECIALIZED IN AERONAUTICS (AS AN EXAMPLE FIREMEN, RESCUE STAFF). TO THIS END, THE VEHICLE MUST HAVE ON BOARD AN AUTONOMOUS GUIDANCE AND NAVIGATION SYSTEM ABLE TO PRODUCE AN AUTONOMOUS LIFTING OFF, TO GUIDE IT TO THE AREA TO BE MONITORED, ESPECIALLY IN THE CASE IN WHICH THIS AREA IS NOT EASILY ACCESSED OR DANGEROUS, TO MANEOUVRE AND PERFORM REPETITIVE PATTERNS OVER THE OBSERVED AREA, AND FINALLY TO PRODUCE AN AUTONOMOUS LANDING. THE MAIN OBJECTIVE OF THIS PROPOSAL IS THE DESIGN AND REALIZATION OF AN ON-BOARD AUTONOMOUS NAVOGATION SYSTEM, BASED ON THE INTEGRATION OF INERTIAL SENSORS AND GPS RECEIVERS, CAPABLE OF CONTINOUSLY MEASURING THE VEHICLE FLIGHT STATE IN ORDER TO TRACK PREFIXED TRAJECTORIES OR TRAJECTORIES AUTONOMOUSLY OR ON GROUND UPDATED DURING THE FLIGHT. THIS RESEARCH ACTIVITY WILL BE IN SYNERGY WITH OTHER PROJECTS CONCERNING THE NAVIGATION AND CONTROL OF UNMANNED VEHICLES AND THE DEVELOPMENT OF ADVANCED OPTICAL SENSORS FOR AIRBIRNE REMOTE SENSING UNDER REALIZATION AT THE GUIDANCE, NAVIGATION AND CONTROL LABORATORY AT DISIS. THIS PROPOSAL FORESEES BOTH THE DESIGN AND DEVELOPMENT AND PRELIMINARY TEST OF THE AUTONOMOUS NAVIGATIONN SYSTEM. THE RELATED ACTIVITIES, TO BE DEVELOPED WITHIN 12 MONTHS, ARE DIVIDED IN TWO LINES: SYSTEM HARDWARE DEVELOPMENT AND TEST; NAVIGATION ALGORITHMS AND SOFTWARE DEVELOPMENT AND IN-FLIGHT TESTING. PROJECT'S OBJECTIVES ARE IN SYNERGY WITH THOSE OF THE CENTRO REGIONALE DI COMPETENZA FOR ENVIRONMENTAL RISK MANAGEMENT. ALSO, THE DESIGN AND REALIZATION OF AN UAV AS A PLATFORM FOR IN-FLIGHT EXPERIMENTATION AND VALIDATION OF NEW TECHNOLOGIES IS A PROJECT OF THE CIRA (ITALIAN CENTRE FOR AEROSPACE RESEARCH) IN CAPUA (CE), IN COOPERATION WITH SEVERAL INDUSTRIES AND UNIVERSITY DEPARTMENTS
Methodology Developments for FTB_1 Post-flight analysis
No full textThe project deals with the development of innovative approaches for the post flight analysis of flight data aiming at reentry vehicle identification. Specifically, innovative approach are developed relying on an unscented kalman filter for aerodynamics identification of a sub-orbital re-entry vehicle in the framewrok of CIRA PRORA USV project
Archeo - Progetto di massima di un sistema spaziale per l'osservazione in archeologia mediante georadar
No full textIt deals with the preliminary design of a space platform equipped with a radar for sub-surface remote sensing. In the project, platform mass and power budget, and preliminary design have been performed based on state-of-art and advanced technological solutions
SABRINA: System for Advanced Bistatic and Interferometry Applications
No full textThe project deals with the analysis and implementation feasibility of concepts and technologies for the determination with high accuracy of the baseline betwenn two satellites flying in formation for Remote Sensing applications, as required in the SABRINA mission. Specifically, the feasibility of optical-based, RF-based and GPS-based technologies is analysed, and a carrier-based differential GPS technich is implemented to evaluate preliminarily performanc
Performance Evaluation of the UNISAT Attitude Control System
No full textThe microsatellite concept involves obvious limitations in size, weight, and on-board available power. This undoubtedly affects the design of the microsatellite subsystems, whose complexity has to be reduced to limit development times and costs. This paper deals with the analysis of the performance of the UNISAT attitude determination and control system. UNISAT is a joint project of a group of Italian universities aimed at designing and developing a multi-mission microsatellite for scientific and educational purposes. The attitude determination hardware consists of a miniature solid-state horizon sensor, a digital two-axis sun sensor, and a three-axis fiuxgate magnetometer. Three-axis attitude control is performed with three magnetic torquers. Control laws are derived separately for the attitude acquisition and the stationkeeping phases using a linearized analytical model of the microsatellite attitude dynamics. Then, a numerical code, which simultaneously integrates the microsatellite orbital and attitude dynamics and control, is used to analyze the accuracy in the attitude angle determination from the sensor measurements and to test the effectiveness of the proposed control strategy for a range of sun-synchronous orbits and altitudes. Numerical results show that the proposed control techniques allow the satellite attitude acquisition to be performed in about one orbit and the attitude angles are controlled within ±2.5 deg during stationkeeping
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