Lares Mission: Engineering Aspects (original) (raw)

LARES: A New Satellite Specifically Designed for Testing General Relativity

International Journal of Aerospace Engineering, 2015

It is estimated that today several hundred operational satellites are orbiting Earth while many more either have already reentered 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 not only the densest satellite but also the densest known orbiting object in the solar system. That implies that the nongravitational perturbations on its surface will have the smallest effects on its orbit. 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, although passive, with 92 laser retroreflectors on its surface, was a real engineering challenge in terms of both manufacturing and testing. Data acquisition and processing are 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.

LARES Laser Relativity Satellite

2011

After almost three decades since the first idea of launching a passive satellite to measure gravitomagnetism, launch of LARES satellite is approaching. The new developed VEGA launcher will carry LARES in a nominally circular orbit at 1450 km altitude. This satellite, along with the two LAGEOS satellites, will allow to improve a previous measurement of the Lense-Thirring effect by a factor of 10. This important achievement will be a result of the idea of combining orbital parameters of a constellation of laser ranging satellites along with a specific design of LARES satellite. Other key points of the experiment are: the ever improving knowledge of the gravitational field of Earth, in particular the lower degree even zonal harmonics with GRACE satellites, and an accurate estimate of all the classical perturbations such as atmospheric drag and solar radiation pressure. In the paper both the scientific aspects as well as the design consideration will be described.

The LARES 2 satellite: new challenges for design and ground test

Aerotecnica Missili & Spazio, 2018

The 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.

Overview of the LARES Mission: orbit, error analysis and technological aspects

Journal of Physics: Conference Series, 2012

LARES (LAser RElativity Satellite), is an Italian Space Agency (ASI) mission to be launched beginning of 2012 with the new European launch vehicle, VEGA; the launch opportunity was provided by the European Space Agency (ESA). LARES is a laser ranged satellite; it will be launched into a nearly circular orbit, with an altitude of 1450 km and an inclination of 69.5 degrees. The goal of the mission is the measurement of the Lense-Thirring effect with an uncertainty of few percent; such a small uncertainty will be achieved using LARES data together with data from the LAGEOS I (NASA) and LAGEOS II (NASA and ASI) satellites, and because GRACE mission (NASA-CSR and DLR-GFZ) is improving Earth's gravity field models. This paper describes LARES experiment along with the principal error sources affecting the measurement. Furthermore, some engineering aspects of the mission, in particular the structure and materials of the satellite (designed in order to minimize the non-gravitational perturbations), are described.

Preliminary results of LARES mission to test general relativity

The LARES mission was conceived to put an almost perfect test particle into an orbit around Earth that, when the known non-gravitational perturbations are removed, will approximate a geodesic of spacetime. Accurate orbit determination along with the accurate modeling of classical perturbation effects on the orbital dynamics of the satellite are key factors for the success of the mission. According to the theory of General Relativity a current of mass-energy, such as a rotating mass, induces an additional deformation to the spacetime. Thus the Earth, with its rotation, produces a very small perturbation on the node of the orbit. This phenomenon is caused by the gravitomagnetic field and in the case of an orbiting satellite is known as frame dragging or Lense-Thirring effect. To measure this effect with a reasonable accuracy, analysis of LAGEOS and LAGEOS 2 data was already performed back in 2004. For a very accurate test of the Lense-Thirring effect, a third specifically designed satellite was required. Many years after the proposal was submitted, in the year 2008 the Italian Space Agency supported the mission and the European Space Agency Launcher Programme Board approved LARES (LAser RElativity Satellite) as the primary payload to be accommodated for the VEGA Launcher qualification flight. Several university satellites were selected to be launched as secondary payload passengers. The launch, on the 13 th of February 2012, was very successful for both the VEGA and LARES teams, the satellite being released with a very high accuracy into the nominal orbit. In this paper it will be shown that LARES, once the known non-gravitational perturbations are removed, behaves as the best test particle available in the solar system. So it turns out to be the ideal instrument for testing not only fundamental physics, but also for carrying out studies on geodesy and geodynamics. Accurate measurement of the Lense-Thirring effect requires several years of data acquisition because of the presence of some periodical perturbations, but some improvements are expected in the next years over the 2004 measurements obtained with only the two LAGEOS satellites.

The design of lares: A satellite for testing general relativity

2007

Prof. Ignazio Ciufolini (P.I.), University and INFN, Lecce , ITALY ignazio.ciufolini@unile.it Prof. Antonio Paolozzi, Scuola di Ingegneria Aerospaziale and INFN, “Sapienza” University of Rome, ITALY antonio.paolozzi@uniroma1.it Dr. Simone Dell'Agnello, Istituto Nazionale di Fisica Nucleare (INFN), Frascati (Rome), ITALY simone.dellagnello@lnf.infn.it Prof. Isidoro Peroni, Scuola di Ingegneria Aerospaziale, “Sapienza” University of Rome, ITALY isidoro.peroni@uniroma1.it

Engineering and scientific aspects of LARES satellite

Acta Astronautica, 2011

LAser RElativity Satellite (LARES) is an Italian passive satellite designed for the accurate test of a phenomenon predicted by Einstein General Relativity called frame-dragging, or gravitomagnetism, i.e., the Earth angular momentum generates spacetime curvature that causes an additional perturbation of the satellite orbit, called the Lense-Thirring effect. LARES is a laser-ranged satellite of the type of the two LAGEOS satellites already orbiting the Earth. Data from these three satellites will also be used to improve the accuracy in the measurement of the Lense-Thirring effect.

Initial orbit determination results for the LARES satellite

LARES (LAser RElativity Satellite) is a laser-ranged satellite deployed by the Italian Space Agency (ASI). It is a spherical satellite covered with 92 retro-reflectors with a radius of 182 mm. Made of tungsten alloy, its weight is 386.8 kg, making it likely the highest mean density body in the Solar System. LARES was launched on the 13 th of February 2012 and detected by radar soon after separation. Within a few days, it was acquired by laser ranging stations from all over the world. The VEGA launcher performed perfectly in its first flight by injecting the satellite in the nominal orbit with high accuracy. The satellite is performing well, and laser returns are being collected and preprocessed by the laser ranging stations for distribution to the community by the International Laser Ranging Service (ILRS). The LARES data will be used for space geodesy, geodynamics and tests of General Relativity. For what concerns the measurement of the frame-dragging effect, predicted by Einstein General Relativity, several years of observations are required to obtain a very accurate measurement of the effect. Ultimately, LARES has been designed for a few percent test of the frame-dragging effect, or gravitomagnetism. We will describe the mission and report the first orbital parameters determination.