1,721,118 research outputs found
Comparison of optical quality of some passive laser ranged satellites
No full textThe LAser RElativity Satellite (LASER) was launched in 2012 by ASI for studying general relativity. A new mission, LARES 2, will be launched in 2019/2020 on a higher orbit and using a different design of the optical payload. LARES is a target for Satellite Laser Ranging; the passive satellite carries 92 cube corner reflectors that allow to measure with high accuracy the position of the centre of mass of the satellite with respect to the ground stations. Aside from the principal scientific goal, the measurement of the relativistic frame-dragging effect, data from LARES (and in future, from LARES 2) are used also in other research related to the study of gravity, to space geodesy, and to Earth science. The accuracy of the laser ranging depends both on the characteristics of the ground station that is tracking the satellite, on the environmental conditions of the atmosphere during the pass of the satellite, and on the design of the target. Each laser ranging station provides the data collected for a particular satellite in a specific format, called Normal Points (NP) that are released daily. By comparing the quantity of NPs produced by a satellite, and the quality of those datasets, with the NPs produced by other satellites having a similar design (passive, spherical targets), it is possible to assess the quality of the optical design of that satellite. For its main scientific mission, the data of LARES are combined with the data of LAGEOS and LAGEOS 2 satellites, orbiting on much higher orbits and considered two benchmarks for laser ranging. The data of geodetic satellites such as LARES, LAGEOS, Stella and Starlette satellite are used by the scientific community for measurements of space geodesy, for the study of the effect of global climate changes on the rotation of the Earth, and for other research related to Earth science. The availability of high-quality targets for laser ranging will improve the accuracy of the results of the research in all the above scientific fields. In this paper the quality of the satellite laser ranging data from LARES is compared with the data of the LAGEOS satellites, with the data of the Stella/Starlette satellites (on lower orbits) and with the data of AJISAI (orbiting at a similar altitude). This information will provide important information for the design of the new LARES 2 satellite
The Araneus Web-Base Management System
No full textThe paper describes the ARANEUS Wel-Base Management System, a system developed at University Roma Tre, which represents a proposal towards the definition of a new kind of data-repository, designed to manage Web data in the database style. We call a Web-Base a collection of data of heterogeneous nature, and more specifically: (i) highly structured data, such as the ones typically stored in relational or object-oriented database systems; (ii) semistructured data, in the Web style. We can simplify by saying that it incorporates both databases and Web sites. A Web-Base Management System (WBMS) is a system for managing such Web-base
LARES-lab: A thermo-vacuum facility for research and e-Learning: Tests of LARES Satellite Components and Small Payloads for e-Learning
No full textLARES, an Italian Space Agency satellite, has been succeßfully launched in 2012. A small thermo-vacuum facility has been specifically designed and built for testing the optical components of the satellite in simulated space environment. Due to the extremely demanding performances of LARES satellite, the facility has been built using the most up-to-date technology available. In particular Sun, Earth and deep space can be simulated in a ultra high vacuum. When the tests connected with the LARES mißion reduced, it was decided to devote the thermo-vacuum chamber also to didactic activities. The facility was designed to be operated remotely only for some basic operations. The full automation of the facility is in progreß in order to provide the students and the researchers with easy and long term acceß, including also the poßibility to operate remotely from the internet and perform complex tests. The students will then have a big opportunity to learn in practice all the aspects of thermo-vacuum testing, which are of paramount importance in the space industry. It will be poßible to perform thermal tests from either the claßroom or home, by exposing the specimen for a specified amount of time, toward Earth, Sun or deep space simulators. They will collect preßures and temperatures and will input additional thermal power through resistive heaters. The paper will first describe the facility and its capabilities showing the tests performed on the LARES satellite components, then will focus mainly on the planned upgrades that will improve its remote use both for research and e-learning
Earth rotation: An example to teach rigid body motion and environmental monitoring: A fallout of the exploitation of LARES satellite data
No full textThe use of satellite laser ranging in combination with other space geodetic techniques allows us to determine Earth's motion with unprecedented accuracy, which is not as simple as usually described in basic textbooks. Besides rotation and revolution there is a wobble of the rotation axis that can be derived by the torque free case in rigid body dynamics. The presence of gravitational perturbations complicates the motion and considering Earth as non-rigid introduces even more variations in the basic Earth motion theory. What is interesting is that also the mass redistribution of air and water on the planet can affect the motion of Earth's rotational axis. Thanks to the millimetre accuracy achievable today, it is possible to correlate very small anomalous rotational axis displacements with global environmental changes such the change in ice melting. The paper will show the experimental motion of the Earth rotation axis and interpret it with the use of the Euler rigid body equations of motion, outlining also the effects of the gravitational perturbations of other bodies in the solar system and of the global climate changes on the Earth rotational axis
Contribution of LARES and geodetic satellites on environmental monitoring
No full textLARES is the latest laser ranged geodetic satellite launched in orbit. It is an Italian Space Agency mission devoted mainly to test fundamental physics. However, it will be shown in the present paper that it will also contribute significantly to Earth science. The use of LARES together with the constellation of the other geodetic satellites will provide improvements in the measurement of the gravity field of Earth including its temporal variation measurements. In particular the latter carries signatures of mass redistribution due to several phenomena including global atmospheric and oceanic circulation, useful not only for monitoring global climate change but also to provide a means for climate model validation
The LARES 2 satellite: new challenges for design and ground test
No full textThe laser-ranging technique and an extremely precise knowledge of the Earth gravitational field paved the way to perform very accurate measurements in General Relativity and Earth science using passive satellites. LARES 2 belongs to this category of satellites and is approved by the Italian Space Agency with a possible launch date at the end of 2019. One of the most interesting effects predicted by General Relativity is frame-dragging according to which the inertial reference frames are dragged by currents of mass-energy, such as a rotating mass. Indeed, the Earth rotation produces this effect that has already been measured by a very accurate orbit determination of the LAGEOS and LARES satellites. With this new satellite it will be possible to improve the accuracy of the measurement by one order of magnitude. This very demanding objective can be reached thanks to the unique orbit and the special design of the LARES 2 satellite. The paper will outline the physics behind the experiment and will describe the mission details
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