185 research outputs found
Orbital data analysis on LARES satellite
No full textLARES satellite has been designed for improving the measurement of frame-dragging, a phenomenon predicted by Einstein’s theory of General Relativity (GR). The satellite body has been designed with the unique characteristic to be the densest known object orbiting in in the solar system to minimize all the perturbing forces acting on it. Thanks to this design, apart from the main purpose of using the satellite for the measurement of frame-dragging, the satellite is also used for improving the realization of the terrestrial reference system and other geodetic measurements. In this paper the evolution of the orbital parameters, starting from the launch date, will be analyzed
Tidal Satellite Perturbations and the Lense-Thirring Effect
No full textL. Iorio warmly thanks I. Ciufolini and L. Guerriero. E. C. Pavlis gratefully acknowledges partial support for this project from NASA's Cooperative Agreement NCC 5-339.https://www.jstage.jst.go.jp/article/sokuchi1954/47/1/47_1_169/_articl
On the Measurement of the Lense-Thirring effect using the nodes of the LAGEOS satellites
No full textIn this paper, we provide a detailed description of our recent analysis and determination of the frame-dragging effect obtained using the nodes of the satellites LAGEOS and LAGEOS 2, in reply to the paper "On the reliability of the so-far performed tests for measuring the Lense-Thirring effect with the LAGEOS satellites" by L. Iorio (doi: 10.1016/j.newast.2005.01.001). First, we discuss the impact of the (J)over dot(2n) uncertainties on our measurement and we show that the corresponding error is of the order of 1% of frame-dragging only. We report the result of the orbital simulations and analyses obtained with and without (J)over dot(4) and with a 4 equal to its EIGEN-GRACE02S value plus 12 times its published error, i.e., a (J)ovr dot(4) equal to about 611% of the value adopted in EIGEN-GRACE02S, that is (J)over dot(4) = 6.11 x (-1.41 x 10(-11)) -8.61 x 10(-11). In all these three cases, by also fitting the final combined residuals with a quadratic, we obtain the same value of the measured Lense-Thirring effect. This value differs by only 1% with respect to our recent measurement of the Lense-Thirring effect. Therefore, the error due to the uncertainties in the (J)over dot(2n) in our measurement of the gravitomagnetic effect can at most reach 1%, in complete agreement with our previously published error budget. Our total error budget in the measurement of frame-dragging is about 5% of the Lense-Thirring effect, alternatively even by simply considering the published errors in the (J)over dot(2n) and their recent determinations we get a total error budget of the order of 10%, in complete agreement with our previously published error budget. Furthermore, weexplicitly give the results and plot of a simulation clearly showing that the claim of Iorio's paper that the (J)over dot(2n) uncertainty may contribute to up a 45% error error in our measurement is clearly unsubstantiated. We then present a rigorous proof that any "imprint" or "memory" effect of the Lense-Thirring effect is completely negligible on the even zonal harmonics produced using the GRACE satellites only and used on the orbits of the LAGEOS satellites to measure the frame-dragging effect. In this paper we do not discuss the problem of the correlation of the Earth's even zonal harmonics since it only refers to our previous, 1998, analysis with EGM96 and it will be the subject of a different paper; nevertheless, we stress that in the present analysis with EIGENGRACE02S the total error due to the static Earth gravity field has been calculated by pessimistically summing up the absolute values of the errors due to each Earth's even zonal harmonic uncertainty, i.e., we have not used any covariance matrix to calculate the total error but we have just considered the worst possible contribution of each even zonal harmonic uncertainty to the total error budget. We also present and explain our past work on the technique of measuring the Lense-Thirring effect using the LAGEOS nodes and give its main references. Finally we discuss some other minor points and misunderstandings of the paper by Iorio, including some obvious mistakes contained both in this paper and in some other previous papers of Iorio. In conclusion, the criticisms in Iorio's paper are completely unfounded and misdirected: the uncertainties arising from the possible variations of the (J)over dot(2n) are fully accounted for in the error budget that we have published. (C) 2005 Elsevier B.V. All rights reserve
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
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
El Niño effects on earth rotation parameters from LAGEOS and LARES orbital analysis
No full textEarth rotation, besides external actions due to other bodies in the solar system, is influenced by internal mass redistributions, including its atmospheric and water envelope. EI Nifio-Southern Oscillation (ENSO) is one such event characterized by sea level change in the eastern part of the Pacific Ocean due to an increase of the temperature by about 2°C. ENSO is manifested with irreguIar periodicity and with different strength. SateIIite Laser Ranging (SLR) to orbiting satellites such as LAGEOS and LARES in conjunction with the other geodedic techniques, such as GNSS and Very Long Baseline Interferometry (VLBI), allow very accurate determination of the center of mass and rotation vector of the Earth. The paper will report on the experimental vaIues of the Earth orientation parameters and in particuIar of the center of mass and the Iength of the day with particuIar reference to signatures due to last ENSO event ended in 2016
Monitoring global climate change using SLR data from LARES and other geodetic satellites
No full textThe Earth Orientation Parameters (EOP), i.e. the spin axis of the Earth, is influenced by the mass redistribution inside and on the surface of the Earth. On the Earth surface, global ice melting, sea level change and atmospheric circulation are the prime contributors. Recent studies have unraveled the majority of the mysteries behind the Chandler wobble, the annual motion and the secular motion of the pole. The differences from the motion of a pole for a rigid Earth is indeed due to the mass redistribution and transfer of angular momentum among the atmosphere, the oceans and solid Earth. The technique of laser ranging and the use of laser ranged satellites such as LARES along with other techniques such Very Long Baseline Interferometry (VLBI) allow to measure the EOP with accuracies at the level of ~200 μas which correspond to few millimeters at the Earth's surface, while the use of Global Navigation Satellite System (GNSS) data can reach an accuracy even below 100 μas. At these unprecedented high levels of accuracy, even tiny anomalous behavior in EOP can be observed and thus correlated to global environmental changes such as ice melting on Greenland and the polar caps, and extreme events that involve strong ocean-atmosphere coupling interactions such as the El Niño. The contribution of Satellite Laser Ranging (SLR) data such as from the LARES mission and similar satellites to this area is outlined in this paper
Effects of climate change on earth’s parameters - an example of exabyte-sized system
No full textClimate change at global scale affects Earth characteristics that can be detected by measuring global parameters such as Earth rotation and centre of mass variations. Similarly, changes in the harmonics of Earth's gravitational field model are an indication of environmental changes and provide a measure of the mass redistributions causing these variations. There are four independent space geodetic techniques today that monitor Earth's geometric and dynamic parameters very accurately: Very Long Baseline Interferometry (VLBI), Satellite/Lunar Laser Ranging (SLR/LLR), Global Navigation Satellite Systems (GNSS) and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS). These techniques have been operational for decades, collecting a very large amount of data that after appropriate processing provide, among other things, the Earth geometric and dynamic parameters used in global climate change monitoring. The same techniques are also necessary for the establishment and maintenance of the International Terrestrial Reference Frame (ITRF). To make the large amount of data more easily usable, scientists and engineers employ reduction techniques to significantly reduce the amount of raw data with minimal loss of information. It will be shown that the total amount of data available today is of the order of exabyte. Due to the complexity of data management and processing several national and international bodies have been established
Quality assessment of LARES satellite ranging data
No full textLARES is an Italian Space Agency mission designed to test General Relativity in the weak field of Earth. In particular, the satellite will be able to measure frame-dragging with an accuracy of about 1%. The difficulty of the measurement is mainly due to the perturbations acting on the satellite and the relatively tiny size of the effect, amounting to about 118 milliarcseconds/year. LARES will also provide data to geodesists and it will contribute to GNSS by improving the origin definition of the International Terrestrial Reference Frame. The mission was designed and the satellite subsystems built and tested in less than four years. The short time to launch and the very limited budget of the LARES mission, raised doubts whether LARES could be, as expected by design, one of the best satellite laser ranging targets. The best way to confirm the success of the mission is to look at the range residuals from the primary stations of the International Laser Ranging Service (ILRS). In the paper it will be shown that from the majority of these stations LARES behaves as the best target
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