1,721,035 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 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
FBG optical sensors for environmental tests of microsatellites
No full textThe use of Fiber Bragg grating sensors is growing in many fields thanks to their properties such as the immunity to electric and magnetic fields and the capability to realize a distributed network of sensors exploiting the multiplexing capabilities. In this paper the use of FBG sensors during the environmental tests performed on a specimen in the thermo-vacuum chamber of the LARES-LAB will be presented. The test chamber has been realized for the optical tests of the LARES satellite, launched in 2012 and now, thanks to the small size of the test chamber, the facility can be proficiently used for testing small satellites as cubesats and nanosats. The chamber has been upgraded adding an optical feed-through suitable for the use of FBG sensors that will let the real-time monitoring of the conditions of the test. A test campaign will be described and a specimen will be monitored using both optical strain gauges and standard sensors, thermal and mechanical stress will be applied in order to perform a comparison of the behavior of the two types of sensors. The validation of the performances of the FBG sensors could open the road for a new methodology for testing satellites with a cheaper and more accurate stress monitoring system. Copyright © 2016 by the International Astronautical Federation (IAF). All rights reserved
Temperature monitoring of thermal-vacuum tests with optical fiber sensors. Preliminary results
No full textLARES-lab is a facility located at Sapienza University of Rome for testing nano-satellites and small payloads in simulated space environment. The facility is equipped with a small cubic thermal-vacuum chamber with an internal volume 60x60x60 cm, capable of reaching very high vacuum conditions. The chamber simulates radiation thermal exchanges toward deep space with nitrogen cooled shrouds and solar radiation with a Sun simulator lamp. An Earth infrared disc simulator is also available. Several tests of payloads and nanosatellites have been already performed in the LARES-lab. Recently the chamber has been upgraded with the installation of an optical fibre feed through for use with Fibre Bragg Gratings (FBGs) for temperature monitoring during the tests. In this paper, some preliminary results on the calibration of the FBG sensor are reported. Issues concerning the coating of the sensor and the values of the thermo optical characteristicsare also pointed out in the paper
TEMPERATURE MONITORING OF THERMAL-VACUUM TESTS WITH OPTICAL FIBRE SENSORS. PRELIMINARY RESULTS
No full textLARES-lab is a facility located at Sapienza University of Rome for testing nano-satellites and small payloads in
simulated space environment. The facility is equipped with a small cubic thermal-vacuum chamber with an internal
volume 60x60x60 cm, capable of reaching very high vacuum conditions. The chamber simulates radiation thermal
exchanges toward deep space with nitrogen cooled shrouds and solar radiation with a Sun simulator lamp. An Earth
infrared disc simulator is also available. Several tests of payloads and nanosatellites have been already performed in
the LARES-lab. Recently the chamber has been upgraded with the installation of an optical fibre feed through for use
with Fibre Bragg Gratings (FBGs) for temperature monitoring during the tests. In this paper, some preliminary
results on the calibration of the FBG sensor are reported. Issues concerning the coating of the sensor and the values
of the thermo optical characteristicsare also pointed out in the paper
Thermal deformation on a laser retro-reflector of LARES satellite: error analysis
No full textLARES is an Italian Space Agency satellite that was successfully put in orbit with the qualification launch of VEGA. The surface of the satellite is covered with 92 Cube Corner Reflectors (CCRs) that allow its precise positioning through the measurements of the International Laser Ranging Service. By measuring the time of flight of the laser pulses sent towards the satellite it is possible to reach ranging accuracies of few millimeters from the best
stations. LARES is passive and as such it does not have thermal control. Thermal deformations of the CCRs can be calculated if power input, boundary conditions and thermal heat transfer parameters are known. The reflecting performances of CCRs are typically evaluated through the analysis of the Far Field Diffraction Pattern (FFDP) which provides information on the energy distribution, of the reflected laser pulse, on the ground. The CCR deformations
can change the FFDP thus reducing the probability to have good laser returns to the station. Due to its particular CCR mounting system, that minimizes contact with the CCR, heat transfer of the CCR is mainly governed by radiation. It is therefore important to evaluate experimentally the solar absorptivity α_s and the infrared emissivity ε.
The paper will report the error analysis to provide guidelines for an optimized test
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
LARES satellite: the best test particle for testing General Relativity
No full textThe LAser RElativity Satellite (LARES) is an Italian Space Agency laser ranged satellite.
Soon after the successful launch with the VEGA maiden flight on the 13th of February 2012,
the analysis of the ranging data from about 40 stations of the International Laser Ranging
Service (ILRS) started. The satellite is passive and covered with optical Cube Corner
Reflectors (CCRs) that allows the accurate positioning of the satellite, through the laser
pulses sent towards the satellite. Aim of the LARES mission is to test frame-dragging and the
Lense-Thirring effect of General Relativity. According to General Relativity a spinning body
distorts spacetime, dragging the inertial frames around it and the orbital plane of a satellite.
Analysing the data of LARES and LAGEOS satellites starting from the launch date of LARES,
a comparison among the orbits shows that the LARES motion, after removal of the known
non-gravitational perturbations, fits better the theoretical geodesic motion of an ideal test-
particle than any other orbiting object in the solar system. In the paper, the scientific
objectives of the mission and the preliminary results of the analysis will be reported. The
paper will also address the outstanding behaviour of LARES as a test particle for
fundamental physics and geodesy
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
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