91 research outputs found
A remote controllable thermovacuum facility for CubeSats and small payloads
No full textThe paper presents the upgrade of a thermovacuum facility that was originally designed for testing the cube corner reflectors of LARES satellite. The upgrade consists in the possibility to control the tests remotely over the internet. Part of the upgrade is at the design phase and part has been realized. Specifically the turbomulecular and scroll pumps, the PT100 thermal sensors, the strain gages, the switching of the led, recently added inside the chamber along with the videocamera for visual monitoring of the tests, have been already implemented. Those can be accessed
through a public domain VNC software which can be installed free for research and educational purposes. More demanding in terms of cost and reliability is the automation of the manipulator, the control of the liquid nitrogen flow and the switching of the solar simulator. In particular the high power required for the solar simulator suggest to avoid switching on and off the device. It is under investigation the possibility of using a moving screen. A remotely controlled valve that can reliably be The automation and the possibility to control remotely the facility will allow to run tests over the night more easily. Also the possibility to show the facility during operation to large classes and even to let the students to run their own tests from the class, home or anywhere else, under the remote supervision of a tutor will increase significantly the potential of the thermovacuum facility. An example of test using this mode of operation will also be presented
Space debris close approach to LARES satellite
No full textSpace debris represent a big concern for future space activities. Particularly at low Earth orbit there is a concentration of debris. Although the probability of impact are today relatively low some occurrences have been registered. The problem was addressed since the beginning of the space age and international treaties regulate the responsibilities of the spacefaring nations. LARES (LAser RElativity Satellite) mission was launched in 2012 and is currently operational. The scientific requirements and the mission design required a waiver to the European debris mitigation regulation for the launch. To date, four close approaches of LARES with space debris have been registered. In the case of a collision with a debris, the resulting controversial is not predictable. The paper addresses possible legal scenarios in case LARES would be involved in an impact with a space debris
Space debris population on the lares satellite orbit
No full textThe Italian Space Agency LARES satellite has been launched in 2012 with the qualification flight of VEGA. The satellite is passive and is tracked by about 50 stations of the International Laser Ranging Service. The main mission objective is to test frame-dragging of general relativity. During the four years in orbit four close approaches have been notified by The United States Joint Space Operations Center (JSpOC). The evaluation of distances were affected by high uncertainties. It will be shown in the paper that with a more accurate ephemerides evaluation of LARES satellite, distances were actually larger. Nevertheless the issue of space debris is of concern for LARES satellite. Unfortunately, three out of the four space debris are older than 30 years and the fourth one is unknown (maybe it is a part detached from a main object). That implies it will be probably not possible to maneuver them, so that in case a collision will be predicted, nothing can be done to avoid it being also LARES without propulsion and attitude control. This situation will make difficult to assess responsibilities in case a collision would occur. Some legal issues will be examined in the paper. An assessment of the collision risk with the known and estimated debris population at 1450 km altitude orbit with LARES satellite will be performed along with an evaluation of the relative velocity involved in the predicted impact. This last parameter will allow to determine the possible damage to the satellite, the relevant production of further debris ands the variation of the orbital parameters of LARES satellite induced by the impact. Copyright © 2016 by the International Astronautical Federation (IAF). All rights reserved
LARES-LAB: a facility for environmental testing of satellite components and micro-satellites
No full textIn this paper it will be presented a facility that was developed at Sapienza University of Rome for testing the Cube Corner Reflectors and mounting system of LARES satellite. LARES (Laser RElativity Satellite) satellite was launched on February 13th, 2012. It is a passive satellite, with a massive spherical body, carrying 92 Cube Corner Reflectors (CCRs) that allows tracking the satellite using Laser Ranging Technology. One of the reasons for performing the test was the material, never used for the manufacturing a satellite: a tungsten alloy. The LARES-Lab allows to perform tests of small satellite components and small satellites in a simulated space environment
Upgrade of the LARES-lab remote controllable thermo-vacuum facility - lab improvements for remote testing and e-learning
No full textThe LARES-lab facility was specifically designed to perform tests in simulated space environment on the optical payload of the LAser RElativity Satellite (LARES). Since the facility was intended to perform demanding tests, it was equipped with the best technology available at the time. After the launch of LARES the facility was used both for testing payloads and small university satellites and for didactic activities. Testing in simulated space environment is fundamental for the development of a space mission, so a well equipped facility in a university is a precious resource for teaching. At the moment, room dimension and the location limit the access to the lab to a small number of students per lesson. To fully exploit the didactic potential of the LARES-lab an improvement over the remote control operation of the thermo-vacuum chamber is planned. The project, which has been described in a previous paper, is currently under development. A new device implemented is a robotic arm to manipulate some mechanisms and to gain experience for remote controlling other servo mechanisms. This way both researchers and students can operate the facility remotely with minimal need of on site operations. Once the improvements will be fully operational, LARES-lab will allow access to the laboratory didactic activities to a much larger number of students
LARES a new satellite specifically designed for testing general relativity
No full textIt is estimated that today several hundred operational satellites are orbiting Earth while many more either already re-entered the atmosphere or are no longer operational. On the 13th of February 2012 one more satellite of the Italian Space Agency has been successfully launched. The main difference with respect to all other satellites is its extremely high density that makes LARES (LAser RElativity Satellite) not only the densest satellite but even the densest known orbiting object in the solar system. That implies the non-gravitational perturbations on its surface will have the smallest effects on its orbit with respect to all other artificial orbiting objects. Those design characteristics are required to perform an accurate test of frame dragging and specifically a test of Lense-Thirring effect, predicted by General Relativity. LARES satellite is passive and covered with 92 retroreflectors. Laser pulses, sent from several ground stations, allow an accurate orbit determination. Along with this last aspect and the mentioned special design one has to take into account the effects of the Earth gravitational perturbations due to the deviation from the spherical symmetry of the gravitational potential. To this aim the latest determinations of the Earth gravitational field, produced using gravitational data from several dedicated space missions including GRACE, and the combination of data from three laser ranged satellites is used in the LARES experiment. In spite of its simplicity LARES was a real engineering challenge both in term of manufacturing and testing. The launch was performed with the VEGA qualification flight provided by the European Space Agency. Data acquisition and processing is in progress. The paper will describe the scientific objectives, the status of the experiment, the special feature of the satellite and separation system including some manufacturing issues, and the special tests performed on its retroreflectors
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 satellite and its minimization of the thermal forces
No full textHere we show the first results of the satellite LARES (LAser RElativity Satellite) of the Italian Space Agency, launched in February 2012 by the European Space Agency. Thanks to its special design, LARES minimizes the non-gravitational perturbations and the thermal forces better than any other artificial satellite. © 2014 IEEE
The Constellation of LARES and LAGEOS Satellites for Testing General Relativity
No full textLARES was developed under the support of the Italian Space Agency. It has been successfully put in orbit on the 13th February 2012 with the VEGA launcher. The main objective of the LARES mission is to test frame-dragging, with the unprecedented accuracy of about 1%. Frame-dragging is an intriguing phenomenon that together with gravitational waves and other relativistic effects is not predicted by classical Galilei-Newton mechanics and find its explanation in the theory of General Relativity. By determining very accurately the orbit of the constellation constituted by LARES and the two LAGEOS satellites, it is possible to achieve such an objective. In the paper it will be shown that the use of the constellation is not the only ingredient required and in particular LARES needed to be designed at the limit of current technology. Also the most updated and accurate determinations of the gravitational field of Earth are of paramount importance in the test. The paper will describe the main LARES mission components and will show why it is so important the use of a constellation to reach the goal
Engineering challenges of LARES satellite, designed to test the dynamics of general relativity
No full textWith the successful flight of VEGA launcher, a passive laser-ranged satellite for testing general relativity has been put in orbit in 2012. LARES is an Italian Space Agency satellite specifically designed and developed for testing frame dragging, an intriguing prediction of general relativity. The fabric of spacetime is warped by the rotation of a body, e.g. by the Earth’s rotation that drags space and time around it and consequently the orbital plane of a satellite. This last effect is called Lense-Thirring effect and the LARES mission is aimed to measure it with an accuracy of about 1%. The main problem to be solved, in order to reach this objective, is to reduce and to model the classical perturbations, acting on the satellite, at a level well below the Lense-Thirring effect. This has been achieved with the use of a constellation of three laser ranged satellites, a challenging design of the satellite, an optimal choice of the altitude and inclination of the orbit and with the use of the most accurate determinations of the gravitational field of Earth. The paper will describe the mission focusing on the engineering challenges encountered during the development of the program. In particular the extremely high density of the satellite was a concern for the first natural frequency of the satellite and supporting structure that must be higher than 70 Hz
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