558 research outputs found
Innovative Solutions in Nano and Pico-satellite Communications
No full textThis research activity develops in the rapidly and constantly growing field of avionics for small satellites. The relatively widespread availability of low-cost piggyback launch opportunities recently made feasible for a heterogeneous set of entities the access to orbit. Universities, industries, local governments and even amateurs, all became interested in space and the rather unique opportunities offered by its environment. This led to the development of a large number of nano and pico satellite missions, respectively with spacecrafts of mass lower than 10 kg and 1 kg. Such tiny satellites are usually built with commercially available electronic components not specifically qualified for the space environment, allowing for savings along the whole development cycle in recurring and non recurring costs. Design re use extends this approach to the system level, with an aggressive exploitation of existing technologies and, possibly, of space-flown architectures. Communication subsystems, a small but critical set of elements common to every mission, are not exempt from such a philosophy. On board networks, on-board transceivers and antennas, ground stations, and the protocols in between are primary requirements for a spacecraft mission, some of the most specialized and complex ones. Design re-use is then sought at every level, to the point of favoring "old and trusted" technologies in spite of lower performances and reduced flexibility. While this was acceptable for pioneer pico satellite missions, with the growth of scientific goals the traditional trade-offs are not appropriate anymore. Even further, the stream of innovations coming from the ground mobile market is not being adequately exploited and today outdated architectures set, rather than match, mission capabilities and achievable goals. The research aims at finding new solutions to common problems becoming prevalent in this field. Better trade-offs are needed in the ground and flight communication segments and in the elements linking them. Better performances are achievable with an increase in system complexity, always taking into account energy, mass and cost constraint
Optical-Based COTS Data Communication Bus for Satellites
No full textCommercial Off The Shelf (COTS) components are gathering more and more interest from satellite developers thanks
to their lower cost and ease of procurement as compared to space qualified ones.
A number of studies to evaluate the possibility of COTS use in space systems are under way:
they get benefits from the fast evolution of automotive and consumer electronic devices, which makes available
innovative solutions and more reliable systems.
This paper focuses on the analysis of the IrDA (Infrared Data Association) protocol and
and discusses the use of this standard to exchange data between the sub-systems of a
satellite. This technique has many advantages towards other data interfaces such as
CAN or proprietary solutions for low bit rate links, since it reduces the amount of
wiring, keeping the benefits of standard and well documented solutions. We also
analyze cosmic radiation effects and propose an implementation which makes use of commercial
low cost components
Which kind of philosopher was Danilo Pejović?
Get PDFU ovom kratkom prilogu autorica pokušava opisati narav Danila Pejovića kao filozofa. Njegovo bitno obilježje bila je filozofijska i svetovna suverenost.In this short contribution the author tries to describe the nature of Danilo Pejović as a philosopher. His main characteristic was a philosophical and secular sovereignity
Reduced Gravity Control of Small Spacecraft using Control Moment Gyroscopes and On-Off Thrusters
No full textUnited StatesMassachusetts Institute of Technology403ICES403: Extravehicular Activity: OperationsVienna, AustriaTodd F. Sheerin, Massachusetts Institute of Technology, USAJose Gomez, Massachusetts Institute of Technology, USADanilo Roascio, Massachusetts Institute of Technology, USAJeffrey A. Hoffman, Massachusetts Institute of Technology, USAThe 46th International Conference on Environmental Systems was held in Vienna, Austria, USA on 10 July 2016 through 14 July 2016.Large spacecraft like the International Space Station have long benefited from the use of control moment gyroscopes (CMGs) as propellantless angular momentum devices, yet the large size of traditional CMGs generally prevent their application to small spacecraft platforms. Recent advances in the miniaturization of CMGs have motivated Draper and MIT to investigate the use of CMGs as attitude actuators for small spacecraft and for astronaut maneuvering units derived from NASA’s SAFER system. On-off thrusters typical in reaction control systems produce fixed forces and torques over variable on-times, and pointing precision is limited by a deadband arising from minimum torque magnitude and duration. CMGs, by contrast, produce variable torques by gimbaling a fixed-rate flywheel; small gimbal rates correspond to small torques while large gimbal rates correspond to large torques. This wider range of torques can enable smaller deadbands (enhanced pointing precision) as well as improved slewing and disturbance rejection. When applied to small spacecraft with moving parts or to astronaut maneuvering systems, CMGs can provide stability without the use of fuel during dynamic operations that would not be possible with traditional thruster reaction control. Microgravity demonstration of thruster and CMG attitude control with the MIT Synchronized Position Hold, Engage, Reorient Experimental Satellites (SPHERES) facility and Honeybee Robotics miniature CMGs was recently conducted aboard NASA’s Reduced Gravity Aircraft in August 2015 (Technology 138-P). CMG torques and SPHERES thruster torques on the same system were compared both in microgravity and in the laboratory. CMGs repeatedly generated both smaller and larger torques than thrusters alone could provide, indicating their capacity to improve control authority in the SPHERES system
O realismo de Danilo Zolo
Get PDFThe article aims to make an analysis of the main aspects of the thought of Danilo Zolo, who turned 80 in January 2016. Initially, we examine the epistemological foundations of the legal realism proposed by Zolo. Then we deal with the significance of this realism for a possible theory of democracy. Finally, we analyze the contributions of that author to the philosophy of international law, which made him one of the leading thinkers in this area in recent decades.Keywords: philosophy of law, political philosophy, legal realism.O artigo se propõe a fazer uma análise de aspectos centrais do pensamento do jusfilósofo Danilo Zolo, que completou 80 anos em janeiro de 2016. Inicialmente, examina os fundamentos epistemológicos do realismo jurídico proposto por Zolo. Em seguida, aborda a significância desse realismo para uma possível teoria da democracia. Por fim, analisa as contribuições do referido autor para a filosofia do direito internacional, as quais o colocam como um dos mais destacados pensadores desta área nas últimas décadas.Palavras-chave: filosofia do direito, filosofia política, realismo jurídico
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