This work has been developed in the framework of the LARES mission of the Italian Space Agency (ASI). The LARES satellite has been built to test, with high accuracy, the frame–dragging effect predicted by the theory of General Relativity, specifically the Lense–Thirring drag of its node. LARES was the main payload in the qualification flight of the European Space Agency launcher VEGA. A concern arose about the possibility of an impact between the eight secondary payloads among themselves, with LARES and with the last stage of the launcher (AVUM). An impact would have caused failure on the payloads and the production of debris in violation of the space debris mitigation measures established internationally. As an additional contribution, this study allowed the effect of the payload release on the final manoeuvers of the AVUM to be understood.

A fully equipped thermovacuum facility has been designed and assembled at Sapienza University during the development phase of LARES, a satellite of the Italian Space Agency. After the launch of the satellite in year 2012, the facility has been devoted to testing small payloads and cubesats. An upgrade of the facility allows some operations to be performed remotely. It is planned to complete the automation of the operations so that the majority of the tests could be monitored and controlled from home or during the lectures from the class. The paper will describe the facility, some test campaigns performed recently and the recent advances in remote operations.

We present a test of general relativity, the measurement of the Earth’s dragging of inertial frames. Our result is obtained using about 3.5 years of laser-ranged observations of the LARES, LAGEOS, and LAGEOS 2 laser-ranged satellites together with the Earth gravity field model GGM05S produced by the space geodesy mission GRACE. We measure μ=(0.994±0.002)±0.05, where μ is the Earth’s dragging of inertial frames normalized to its general relativity value, 0.002 is the 1-sigma formal error and 0.05 is our preliminary estimate of systematic error mainly due to the uncertainties in the Earth gravity model GGM05S. Our result is in agreement with the prediction of general relativity.

LARES is an Italian Space Agency spherical passive satellite that will test Einstein General Relativity. LARES is about 400 kg in weight and is built with an extremely dense material. This characteristic will make LARES the single known object with the highest mean density in the solar system. This property will allow to drastically reduce the errors in the estimate of the effects of the non gravitational perturbation on the LARES orbit. That, together with the accurate knowledge of the Earth gravitational field and with the laser ranging technique, will allow to obtain the measurement of the Lense-Thirring effect predicted by General Relativity. LARES will be the main payload of the new VEGA launcher. The launch is foreseen in the second half of year 2011. One of the main challenges of the engineering aspects of the mission was the application of the pre-load on the satellite and a way of measuring it. Also due to the high values of this pre-load verification of the pressures applied on the satellite surface by the separation system was needed. In this paper the measurement techniques will be shown, i.e., conventional resistive strain gages and fiber optic sensor. Also a brief overview of the mission will be reported.

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.

Theoretical study of the phenomenon of gravitomagnetism and of its measurement with Lunar Laser Ranging

Current observations of the universe have strengthened the interest to further test General Relativity and other theories of fundamental physics. After an introduction to the phenomenon of frame-dragging predicted by Einstein’s theory of General Relativity, with fundamental astrophysical applications to rotating black holes, we describe the past measurements of frame-dragging obtained by the LAGEOS satellites and by the dedicated Gravity Probe B space mission. We also discuss a test of String Theories of Chern-Simons type that has been carried out using the results of the LAGEOS satellites. We then describe the LARES space experiment. LARES was successfully launched in February 2012 to improve the accuracy of the tests of frame-dragging, it can also improve the test of String Theories. We present the results of the first few months of observations of LARES, its orbital analyses show that it has the best agreement of any other satellite with the test-particle motion predicted by General Relativity. We finally briefly report the accurate studies and the extensive simulations of the LARES space experiment, confirming an accuracy of a few percent in the forthcoming measurement of frame-dragging.

The angular momentum of a central body produces in general relativity an intriguing phenomenon called frame- dragging and induces a secular drift of the node of a satellite called the Lense-Thirring (L-T) effect that is extremely tiny for satellites orbiting around Earth. For the laser-ranged satellite LAGEOS it amounts to about 31 milliarcsec/year. The largest non-relativistic secular effects on the node of satellites are due to the non-sphericity of the terrestrial gravity field, in fact, this effect is several orders of magnitude greater than the L-T effect. By combining the longitudes of the nodes of two satellites: LAGEOS and LAGEOS 2, it is possible to cancel the nodal drift uncertainties due to the first even zonal harmonic, J 2 , reaching an uncertainty of the order of 10%. The LARES (LAser RElativity Satellite) space experiment, funded by the Italian Space Agency (ASI), together with the LAGEOS and LAGEOS 2 satellites will allow an accurate measurement of frame-dragging and Earth's gravitomagnetic field with an accuracy of approximately 1%. However, this measurement will be affected by the uncertainties due to the even zonal harmonics with degree strictly higher than four. The goal of this paper is to present the idea underlying the mission of placing in orbit a second LARES-type satellite: LARES 2. By placing LARES 2 in a supplementary orbit with respect to LARES or with respect to LAGEOS the effect of all the even zonal harmonics will be eliminated thus allowing a reduction on the uncertainty substantially below 1%. Furthermore, both, by measuring the perigee shift of LARES 2, and by processing the data of all the laser-ranged satellites of this constellation, LAGEOS, LAGEOS 2, LARES and LARES 2, it will be possible to put stronger limits on a conceivable Yukawa-type fifth-force as predicted by some alternative fundamental physics theories. Finally, LARES 2 will be an additional target for the International Laser Ranging Service and it will provide a great contribution to Earth science, specifically in improving the International Terrestrial Reference Frame, and in geodesy and geodynamics.

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-re ectors with a radius of 182 mm. Made of tungsten alloy, its weight is 387 kg, making it likely the highest mean density body in the Solar System. LARES was launched on the 13th 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 rst ight by injecting the satellite in the nominal orbit with high accuracy. The measured LARES orbital elements: semimajor axis is 7827 km, orbital eccentricity is 0.0005 and orbital inclination is 69.45 degrees. 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, in particular for the measurement of the frame-dragging eect, predicted by Einstein's gravitational theory; several years of observations are required to obtain a very accurate measurement of the eect. Ultimately, LARES has been designed for a few percent test of the frame-dragging eect, or gravitomagnetism. We will present a preliminary analysis of the LARES orbit determination results based on the laser ranging data collected by the ILRS.

Introduction to the theory of General Relativity

LARES (LAser RElativity Satellite), a scientific satellite of the Italian Space Agency (ASI), has been accurately injected in the nominal orbit by the new ESA expendable launch vehicle, Vega during its qualification launch, on the 13th of February 2012. This was a very exciting result also because of the low success rate of qualification launches . Furthermore, several innovative technical solutions characterize the new European launch vehicle, such as the extensive use of carbon fiber reinforced plastic composites for the rocket structures. LARES program started on February 2008 when the Italian Space Agency awarded a contract to the prime contractor CGS (former Carlo Gavazzi Space). A peculiarity of the LARES program was the extensive involvement of universities in many aspects such as the technical design of the satellite and the innovative separation system. A strong cooperation between ASI and ESA about its respective programs, since the acceptance of the LARES mission for the Vega maiden flight, allowed to design a mission which satisfies the scientific requirements of the satellite along with the launcher qualification objectives. The trajectory itself was defined also taking into account the launch vehicle performance and trajectory constraints. The initial orbit envisaged for the maiden flight was a typical sun-synchronous orbit at about 750 km. However that was not acceptable for the science objectives, i.e., the measurement of the Lense-Thirring effect, an Einstein general relativity prediction. Therefore ESA and the launch vehicle authority, ELV (European Launch Vehicle) Prime Contractor of the VEGA development program, proposed a new orbit at 1200 km that later was changed to 1450 km along with small changes to the inclination in order to comply with all the safety constraints to the mission trajectory. In order to meet part of its qualification requirements, the VEGA upper-stage (AVUM) performed several maneuvers, especially during the ballistic phase, namely: the neutral axis maneuver, the barbeque, sun pointing, and spin axis maneuver. In this paper, an overview of the LARES mission and of its elements, including the payload ground segment, is given, together with the first results of the launch campaign and activities that brought the satellite in the final operative configuration.

The LARES satellite for the study of the Lense-Thirring effect predicted by Einstein general relativity has been launched on the 13th of February 2012 and injected in the nominal orbit with high accuracy. The Italian Space Agency (ASI) and the European Space Agency (ESA) provided the main support to the mission, ASI on the LARES system side and ESA on the launch vehicle side. An important requirement of the satellite was the lowest possible value of the surface-to-mass ratio. This is indeed related to the possibility to reduce the effect of classical surface perturbations on the satellite motion. That was achieved by constructing the highest mean density orbiting body in the solar system, that implied the use of a non conventional material for space. The experience acquired on the bulk tungsten material used for LARES, during the manufacturing of breadboards, improved the knowledge on the machining of this material that was never used, at least as a main component of a satellite and with this dimension, in the aerospace field. The knowledge acquired suggested some improvements in the manufacturing strategy for the Flight unit resulting in even tighter tolerances than in the demonstration unit. Also for the LARES separation system an unconventional design was adopted since no protruding parts were acceptable on the satellite surface. In the paper some detail on the manufacturing processes of LARES satellite will be reported and the final design of the separation system will be described along with some other relevant particular issues.

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.

On February 13th 2012, the LARES satellite of the Italian Space Agency (ASI) was launched into orbit with the qualification flight of the new VEGA launcher of the European Space Agency (ESA). The payload was released very accurately in the nominal orbit. The name LARES means LAser RElativity Satellite and summarises the objective of the mission and some characteristics of the satellite. It is, in fact, a mission designed to test Einstein's General Relativity Theory (specifically ‘frame-dragging' and Lense-Thirring effect). The satellite is passive and covered with optical retroreflectors that send back laser pulses to the emitting ground station. This allows accurate positioning of the satellite, which is important for measuring the very small deviations from Galilei–Newton's laws. In 2008, ASI selected the prime industrial contractor for the LARES system with a heavy involvement of the universities in all phases of the programme, from the design to the construction and testing of the satellite and separation system. The data exploitation phase started immediately after the launch under a new contract between ASI and those universities. Tracking of the satellite is provided by the International Laser Ranging Service. Due to its particular design, LARES is the orbiting object with the highest known mean density in the solar system. In this paper, it is shown that this peculiarity makes it the best proof particle ever manufactured. Design aspects, mission objectives and preliminary data analysis will be also presented.

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

LARES, Laser Relativity Satellite, is a spherical laser-ranged satellite, passive and covered with retroreflectors. It will be launched with ESA’s new launch vehicle VEGA (ESA-ELV-ASI-AVIO) in early 2012. Its orbital elements will be: inclination 70 ◦ ± 1 ◦ , semi-major axis 7830 km and near zero eccentricity. Its weight is about 387 kg and its radius 18.2 cm. It will be the single known most dense body orbiting Earth in the solar system, and the non-gravitational perturbations will be minimized by its very small ’cross-section-to-mass’ ratio. The main objective of the LARES satellite is a test of the frame-dragging effect, a consequence of the gravitomagnetic field predicted by Einstein’s theory of General Relativity. Together with the orbital data from LAGEOS and LAGEOS 2, it will allow a measurement of frame-dragging with an accuracy of a few percent.

contenuti (Abstract) The LARES satellite is an Italian space mission funded by ASI, with CGS as prime contractor and Salento and Sapienza Universities as subcontractors. The LARES will be put into orbit by the European launcher VEGA during its maiden flight, foreseen in year 2011. The paper describes the general features of the material chosen for the manufacturing of the satellite and its components. Particular interest will be devoted to the manufacturing process and analysis of the screws

LARES (LAser RElativity Satellite) is a passive satellite put in orbit by the VEGA launcher the past 13th of February 2012. It is designed for the accurate test of the Lense-Thirring effect. This phenomenon is induced by the Earth rotation that according to Einstein General Relativity drags space-time and consequently the trajectory of orbiting objects. In order to reach the expected results of few percent accuracy in the measurement of that effect, some restrictive scientfic requirements have been imposed with regard to the material to be used for the satellite body (SB) and to the surface properties of the SB itself, giving special attention to the density of the SB (higher than 17900 kg/m3 ). Furthermore to reduce interaction with the magnetic field of Earth some upper limit to, the electrical conductivity of the alloy was specified. All those aspects along with some considerations on the manufacturing challenges of LARES will be reported. Finally the different methods evaluated for the finishing of the SB, so as to satisfy the scientific requirements such as the infrared emissivity (ε) and the solar absorptivity (α) of the surface will be analysed.

The LARES (LAser RElativity Satellite) satellite was successfully launched in February 2012. The LARES space experiment is based on the orbital determinations of the laser ranged satellites LARES, LAGEOS (LAser GEOdynamics Satellite) and LAGEOS 2 together with the determination of the Earth’s gravity field by the GRACE (Gravity Recovery And Climate Experiment) mission. It will test some fundamental physics predictions and provide accurate measurements of the frame-dragging effect predicted by Einstein’s theory of General Relativity. By 100 Monte Carlo simulations of the LARES experiment, with simulations of the orbits of LARES, LAGEOS and LAGEOS 2 according to the latest GRACE gravity field determinations, we found that the systematic errors in the measurement of frame-dragging amount to about 1.4% of the general relativistic effect, confirming previous error analyses.

We present a statistical analysis of the laser ranging data of LAGEOS and LAGEOS 2 satellites which have provided a test of dragging of inertial frames, or frame-dragging, by rotating mass as predicted by General Relativity. As a result, the analysis of the residuals, after filtering out the periodic effects, is consistent with a Gaussian model, with a nonzero mean in agreement with the one predicted by Lense–Thirring effect.

On the occasion of the centanary of its formulation, a description is given of the foundation of General Relativity and of the experimental triumphs achieved by Einstein’s gravitational theory during the last one hundred years. In particular we describe the impressive Solar System tests of General Relativity, some of its important applications to our daily life and the present and future efforts to further test the gravitational interaction.

The LAser RElativity Satellite (LARES) has been successfully launched on the 13th of February 2012 with the VEGA maiden flight. Its main objective is to test an aspect predicted in Einstein General Relativity known as dragging of inertial frames, the Earth rotation by dragging the spacetime will also drag the orbital plane of LARES by a tiny but measurable amount, this is also known as Lense-Thirring effect. The International Laser Ranging Service is providing the ground tracking of the satellite by sending laser pulses and by measuring the relevant return time of flight. Due to the presence of sensible periodical perturbations, it is necessary to analyze several years of data before an accurate test of the Lense-Thirring effect could be performed. Furthermore to eliminate some huge effects of classical gravitational perturbations on the orbital node of LARES, data have to be analyzed together with those of the LAGEOS and LAGEOS 2 satellites, provided also that an accurate determination of the gravitational field of Earth is inserted in the orbital determination programs used in the orbital estimation. In this paper the physics underlying the experiment will be recalled and the ground operations and all the experimental activities performed to acquire the orbital data of the satellite will be described.

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.

In this paper we respond to the criticisms of "Phenomenology of the Lense-Thirring effect in the Solar System" by lorio et al. about the general relativistic phenomena of gravitomagnetism and frame-dragging. The claims of the paper by lorio et al. are not reproducible in any of our independent analyses. (C) 2011 Elsevier B.V. All rights reserved.

The LARES satellite was successfully launched in 2012 for tests of General Relativity and gravitational physics including the accurate measurement of frame-dragging. It is currently very well observed all over the world by the stations of the International Laser Ranging Service. Its preliminary orbital analyses show that LARES behaves as the best artificial massive test particle today available in the solar system, providing an optimal approximation to the time-like geodesic motion of General Relativity. Furthermore, on the basis of a test using almost three years of observations of LARES, we concluded that LARES, together with the LAGEOS and LAGEOS 2 satellites, provides excellent preliminary results for testing 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 pacetime. 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 13th 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 precession of the orbital node of a particle orbiting a rotating mass is known as Lense-Thirring effect (LTE) and is a manifestation of the general relativistic phenomenon of dragging of inertial frames or frame-dragging. The LTE has already been measured by using the node drifts of the LAGEOS satellites and GRACE-based Earth gravity field models with an accuracy of about 10% and will be improved down to a few percent with the recent LARES experiment. The Galileo system will provide 27 new node observables for the LTE estimation and their combination with the LAGEOS and LARES satellites can potentially reduce even more the error due to the mismodeling in Earth’s gravity ?eld. However, the accurate determination of the Galileo orbits requires the estimation of many different parameters, which can absorb the LTE on the orbital nodes. Moreover, the accuracy of the Galileo orbits and hence, of their node drifts, is mainly limited by the mismodeling in the Solar Radiation Pressure (SRP). Using simulated data we analyze the effects of the mismodeling in the SRP on the Galileo nodes and propose optimal orbit parameterizations for the measurement of the LTE from the future Galileo observations.

LARES Satellite has been successfully launched on February 13th 2012 with the first flight of the new European Launcher VEGA. The passive, laser ranged satellite carries 92 cube corner reflectors (CCR). Due to its high density LARES represents the known orbiting object with the highest mean density in the solar system. This property makes it an almost perfect proof particle in the gravitational field of Earth. LARES is now operational and it is tracked by the International Laser Ranging Service stations. It will be used to test General Relativity and in particular the fact that the rotating Earth drags spacetime. The satellite design is quite innovative in the use of tungsten alloy as a structural material; indeed, the satellite body has been machined from a single piece of high density sintered alloy. The sintered alloy is characterized by a porous surface that shall be carefully cleaned before the integration of the optical components, in order to avoid contamination of the back faces of the CCR from the metal. Two cleaning procedures have been identified, to be performed on LARES. One procedure consisted in chemical cleaning with different solvents and cleaning agents; the second procedure consisted in a chemical cleaning followed by degassing in a high vacuum oven. The cleanness procedures have been tested on breadboards reproducing the satellite materials. The breadboards were tungsten alloy cylinders, carrying a cube corner reflector. The test was performed on two different breadbords each one for one of the two cleaning procedure. To simulate the operative space conditions the Thermal Vacuum Facility of Sapienza University of Rome has been used. The breadboards were maintained in simulated space environment to allow degassing of possible contaminants from the metal and possible detachment of contaminants from the metal to the back faces of the CCR. Visual inspection and Far Field Diffraction Patter tests have been performed to verify the possible presence and effect of contaminants on the of the CCR back faces. In the paper some detail on the LARES mission and on the scientific objectives will be described along with all the details on this qualification process.

We apply the Kolmogorov statistic to analyse the residual data of two LAGEOS satellites on General Relativistic Lense-Thirring effect, and show that it reveals a tiny difference in the properties of the satellites, possibly related to Yarkovsky-Rubincam e?ect. The recently launched LAser RElativity Satellite (LARES) can provide constraints to the extensions of General Relativity such as the Chern-Simons (CS) gravity with metric coupled to a scalar field through the Pontryagin density, so an explicit dependence on the frame dragging measurements vs. the CS parameter is given.

LARES satellite was launched on the 13th of February 2012 using the new European Space Agency (ESA) launcher VEGA from Kourou Spaceport in French Guyana. LARES is a passive satellite of the Italian Space Agency (ASI) devised and designed by the University of Salento and Sapienza to measure with high accuracy the effect of the Earth angular momentum on the spacetime geometry and on the orbital motion of a satellite. This effect is called frame-dragging or Lense-Thirring effect and was published in 1918 using Einstein’s equations soon after the publication of general relativity. Because of its design, optimized to minimize the non gravitational perturbations, LARES is the known single object orbiting in the solar system with the highest mean density. The LARES experiment is indeed performed also with two more satellites LAGEOS (NASA) and LAGEOS 2 (NASA and ASI). Before the launch it was studied the possibility either to depose a thin film or to paint the satellite in such a way to perform a passive temperature control of the satellite. In the paper all the different options considered and the actual final choice decided for LARES surface treatment will be described.

LARES-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.

The Laser Relativity Satellite is built from a specifically chosen, dense tungsten alloy and is covered with laser retroreflectors to test general relativity and fundamental physics.

The discovery of the accelerating expansion of the Universe, thought to be driven by a mysterious form of “dark energy” constituting most of the Universe, has further revived the interest in testing Einstein’s theory of General Relativity. At the very foundation of Einstein’s theory is the geodesic motion of a small, structureless test-particle. Depending on the physical context, a star, planet or satellite can behave very nearly like a test-particle, so geodesic motion is used to calculate the advance of the perihelion of a planet’s orbit, the dynamics of a binary pulsar system and of an Earth-orbiting satellite. Verifying geodesic motion is then a test of paramount importance to General Relativity and other theories of fundamental physics. On the basis of the first few months of observations of the recently launched satellite LARES, its orbit shows the best agreement of any satellite with the test-particle motion predicted by General Relativity. That is, after modelling its known non-gravitational perturbations, the LARES orbit shows the smallest deviations from geodesic motion of any artificial satellite: its residual mean acceleration away from geodesic motion is less than 0.5 × 10−12 m/s2. LARES-type satellites can thus be used for accurate measurements and for tests of gravitational and fundamental physics. Already with only a few months of observation, LARES provides smaller scatter in the determination of several low-degree geopotential coefficients (Earth gravitational deviations from sphericity) than available from observations of any other satellite or combination of satellites.

Laser ranging, both Lunar (LLR) and Satellite Laser Ranging (SLR), is one of the most accurate techniques to test gravitational physics and Einstein's theory of General Relativity. Lunar Laser Ranging has provided very accurate tests of both the strong equivalence principle, at the foundations of General Relativity, and of the weak equivalence principle, at the basis of any metric theory of gravity; it has provided strong limits to the values of the so-called PPN (Parametrized Post-Newtonian) parameters, that are used to test the post-Newtonian limit of General Relativity, strong limits to conceivable deviations to the inverse square law for very weak gravity and accurate measurements of the geodetic precession, an effect predicted by General Relativity. Satellite laser ranging has provided strong limits to deviations to the inverse square gravity law, at a different range with respect to LLR, and in particular has given the first direct test of the gravitomagnetic field by measuring the gravitomagnetic shift of the node of a satellite, a frame-dragging effect also called Lense-Thirring effect. Here, after an introduction to gravitomagnetism and frame-dragging, we describe the latest results in measuring the Lense-Thirring effect using the LAGEOS satellites and the latest gravity field models obtained by the space mission GRACE. Finally, we describe an update of the LARES (LAser RElativity Satellite) mission. LARES is planned for launch in 2011 to further improve the accuracy in the measurement of frame-dragging.

LARES 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.

Satellite Laser Ranging (SLR) makes an important contribution to Earth science providing the most accurate measurement of the long-wavelength components of Earth’s gravity field, including their temporal variations. Furthermore, SLR data along with those from the other three geometric space techniques, Very Long Baseline Interferometry (VLBI), Global Navigation Satellite Systems (GNSS) and DORIS, generate and maintain the International Terrestrial Reference Frame (ITRF) that is used as a reference by all Earth Observing systems and beyond. As a result we obtain accurate station positions and linear velocities, a manifestation of tectonic plate movements important in earthquake studies and in geophysics in general. The “geodetic” satellites used in SLR are passive spheres characterized by very high density, with little else than gravity perturbing their orbits. As a result they define a very stable reference frame, defining primarily and uniquely the origin of the ITRF, and in equal shares, its scale. The ITRF is indeed used as “the” standard to which we can compare regional, GNSS-derived and alternate frames. The melting of global icecaps, ocean and atmospheric circulation, sea-level change, hydrological and internal Earth-mass redistribution are nowadays monitored using satellites. The observations and products of these missions are geolocated and referenced using the ITRF. This allows scientists to splice together records from various missions sometimes several years apart, to generate useful records for monitoring geophysical processes over several decades. The exchange of angular momentum between the atmosphere and solid Earth for example is measured and can be exploited for monitoring global change. LARES, an Italian Space Agency (ASI) satellite, is the latest geodetic satellite placed in orbit. Its main contribution is in the area of geodesy and the definition of the ITRF in particular and this presentation will discuss the improvements it will make in the aforementioned areas.

In this letter, we reply to the preceding paper by Iorio (EPL, 96 (2011) 30001 (this issue)), hereafter referred to as I2011, where we address criticisms regarding the Lense-Thirring frame-dragging experiment results obtained from the laser ranging to the two LAGEOS satellites. Copyright (C) EPLA, 2011

LARES 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.

LARES Satellite has been conceived adopting an innovative design. The main body of the satellite is in fact made of one single piece of tungsten alloy. It is a passive satellite and it has been launched successfully on the 13th of February 2012 with the first flight of the new launcher, VEGA. LARES mission has been developed for testing Einstein general relativity and in particular the Lense-Thirring effect. LARES weights almost 400 kg and its surface is covered with 92 cube corner reflectors (CCR s) made of fused silica. The satellite orbit is reconstructed using the data collected by laser ranging stations belonging to the International Laser Ranging Service. This innovative design, due to the particular material used, needed accurate testing of the optical components because of the high temperatures expected on the satellite operative life. A series of tests to qualify the design have been performed in the Thermal Vacuum Chamber of Sapienza University in Rome. In this paper the results will be summarized.

Is time travel possible? What is Einstein’s theory of relativity mathematically predicting in that regard? Is time travel related to the so-called clock ‘paradoxes’ of relativity and if so how? Is there any accurate experimental evidence of the phenomena regarding the different flow of time predicted by General Relativity and is there any possible application of the temporal phenomena predicted by relativity to our everyday life? Which temporal phenomena are predicted in the vicinities of a rotating body and of a mass-energy current, and do we have any experimental test of the occurrence of these phenomena near a rotating body? In this paper, we address and answer some of these questions.

LARES (LAser RElativity Satellite) is a passive satellite, it was launched on February 13, 2012 using the new European Space Agency (ESA) launcher VEGA, to measure with high accuracy the effect of the Earth angular momentum on the spacetime geometry that in turn affect the orbital motion of a satellite. This effect is called frame-dragging or Lense-Thirring effect. The reduction of the surface-to-mass ratio is the most important parameter in this respect. A tungsten alloy has been chosen as the best cost effective solution. The LARES 2 mission has been recently proposed aiming at the construction and launch of a second LARES satellite which, in one possible configuration, has a larger diameter and mass. During the LARES manufacturing some issues related to the low fracture toughness of tungsten alloys were evident, the most critical parts being the screws used in the retroreflectors mounting system. The aim of this work, on the basis of all these considerations, is to measure the fracture toughness of this alloy in order to evaluate, in a second stage, feasible thermomechanical treatments that should be able to increase safety margins.

Even though originally designed for testing frame-dragging as predicted by general relativity, LARES satellite data are widely exploited also for Earth science. Being a passive satellite, its contribution is expected to continue for several decades. Geodesy, geodynamics and the International Terrestrial Reference Frame (ITRF) use an ensemble of techniques including Satellite Laser Ranging (SLR), Very Long Baseline Interferometry (VLBI) and microwave tracking of Global Navigation Satellite Systems (GNSS), to generate scientific products useful in Earth System monitoring. Initially, passive geodetic satellites pioneered, among other things, the determination of plate tectonic motion and the accurate observation of the long wavelength gravitational field of Earth. The recent additions to this group of passive SLR targets will result in further improvement of the reference frame, which in turn will have an impact in many other areas, from global environmental monitoring to more accurate GNSS positioning. In fact phenomena such as sea level change, global ice melting and angular momentum exchange between the atmosphere and solid Earth provide useful information for global climate change. The paper will present recent results in the field of Earth science obtained with the contribution of LARES satellite data.