59 research outputs found
SLR tracking of GPS-35
An experiment was designed to launch a corner cube retroreflector array on one of the Global Positioning Satellites (GPS). The launch on Aug. 31, 1993 ushered in the era of SLR tracking of GPS spacecraft. Once the space operations group finished the check-out procedures for the new satellite, the agreed upon SLR sites were allowed to track it. The first site to acquire GPS-35 was the Russian system at Maidanak and closely after the MLRS system at McDonald Observatory, Texas. The laser tracking network is currently tracking the GPS spacecraft known as GPS-35 or PRN 5 with great success. From the NASA side there are five stations that contribute data regularly and nearly as many from the international partners. Upcoming modifications to the ground receivers will allow for a further increase in the tracking capabilities of several additional sites and add some desperately needed southern hemisphere tracking. We are analyzing the data and are comparing SLR-derived orbits to those determined on the basis of GPS radiometric data
The impact of tidal errors on the determination of the Lense-Thirring effect from satellite laser ranging
The general relativistic Lense-Thirring effect can be detected by means of a
suitable combination of orbital residuals of the laser-ranged LAGEOS and LAGEOS
II satellites. While this observable is not affected by the orbital
perturbation induced by the zonal Earth solid and ocean tides, it is sensitive
to those generated by the tesseral and sectorial tides. The assessment of their
influence on the measurement of the parameter mu, with which the
gravitomagnetic effect is accounted for, is the goal of this paper. After
simulating the combined residual curve by calculating accurately the
mismodeling of the more effective tidal perturbations, it has been found that,
while the solid tides affect the recovery of mu at a level always well below
1%, for the ocean tides and the other long-period signals Delta mu depends
strongly on the observational period and the noise level: Delta mu(tides)
amounts to almost 2% after 7 years. The aliasing effect of K1 l=3 p=1 tide and
SRP(4241) solar radiation pressure harmonic, with periods longer than 4 years,
on the perigee of LAGEOS II yield to a maximum systematic uncertainty on
\m_{LT} of less than 4% over different observational periods. The zonal
18.6-year tide does not affect the combined residuals.Comment: 24 pages, 4 tables, 6 figures, submitted to Int. Journal of Mod.
Phys. D. Changes in auctorship, references and conten
A new laser-ranged satellite for General Relativity and space geodesy: I. An introduction to the LARES2 space experiment
We introduce the LARES 2 space experiment recently approved by the Italian Space Agency (ASI). The LARES 2 satellite is planned for launch in 2019 with the new VEGA C launch vehicle of ASI, ESA and ELV. The orbital analysis of LARES 2 experiment will be carried out by our international science team of experts in General Relativity, theoretical physics, space geodesy and aerospace engineering. The main objectives of the LARES 2 experiment are gravitational and fundamental physics, including accurate measurements of General Relativity, in particular a test of frame-dragging aimed at achieving an accuracy of a few parts in a thousand, i.e., aimed at improving by about an order of magnitude the present state-of-the-art and forthcoming tests of this general relativistic phenomenon. LARES 2 will also achieve determinations in space geodesy. LARES 2 is an improved version of the LAGEOS 3 experiment, proposed in 1984 to measure frame-dragging and analyzed in 1989 by a joint ASI and NASA study
Fundamental Physics and General Relativity with the LARES and LAGEOS satellites
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.Comment: To be publihed in Nuclear Physics. arXiv admin note: substantial text
overlap with arXiv:1306.1826, arXiv:1211.137
A Test of General Relativity Using the LARES and LAGEOS Satellites and a GRACE Earth's Gravity Model
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's gravity field model GGM05S produced by the
space geodesy mission GRACE. We measure ,
where 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 the
estimated systematic error mainly due to the uncertainties in the Earth's
gravity model GGM05S. Our result is in agreement with the prediction of General
Relativity.Comment: 13 pages, 4 figures, published on EPJ
LARES Satellite Thermal Forces and a Test of General Relativity
We summarize a laser-ranged satellite test of frame-dragging, a prediction of
General Relativity, and then concentrate on the estimate of thermal thrust, an
important perturbation affecting the accuracy of the test. The frame dragging
study analysed 3.5 years of data from the LARES satellite and a longer period
of time for the two LAGEOS satellites. Using the gravity field GGM05S obtained
via the Grace mission, which measures the Earth's gravitational field, the
prediction of General Relativity is confirmed with a 1- formal error of
0.002, and a systematic error of 0.05. The result for the value of the frame
dragging around the Earth is = 0.994, compared to = 1 predicted by
General Relativity. The thermal force model assumes heat flow from the sun
(visual) and from Earth (IR) to the satellite core and to the fused silica
reflectors on the satellite, and reradiation into space. For a roughly current
epoch (days 1460 - 1580 after launch) we calculate an average along-track drag
of -0.50 .Comment: 6 pages, multiple figures in Proceedings of Metrology for Aerospace
(MetroAeroSpace), 2016 IEE
Measuring the relativistic perigee advance with Satellite Laser Ranging
One of the most famous classical tests of General Relativity is the
gravitoelectric secular advance of the pericenter of a test body in the
gravitational field of a central mass. In this paper we explore the possibility
of performing a measurement of the gravitoelectric pericenter advance in the
gravitational field of the Earth by analyzing the laser-ranged data to some
existing, or proposed, laser-ranged geodetic satellites. At the present level
of knowledge of various error sources, the relative precision obtainable with
the data from LAGEOS and LAGEOS II, suitably combined, is of the order of
. Nevertheless, these accuracies could sensibly be improved in the
near future when the new data on the terrestrial gravitational field from the
CHAMP and GRACE missions will be available. The use of the perigee of LARES
(LAser RElativity Satellite), in the context of a suitable combination of
orbital residuals including also LAGEOS II, should further raise the precision
of the measurement. As a secondary outcome of the proposed experiment, with the
so obtained value of \ppn and with \et=4\beta-\gamma-3 from Lunar Laser
Ranging it could be possible to obtain an estimate of the PPN parameters
and at the level.Comment: LaTex2e, 14 pages, no figures, 2 tables. To appear in Classical and
Quantum Gravit
A new laser-ranged satellite for General Relativity and space geodesy: IV. Thermal drag and the LARES 2 space experiment
In three previous papers we presented the LARES 2 space experiment aimed at a
very accurate test of frame-dragging and at other tests of fundamental physics
and measurements of space geodesy and geodynamics. We presented the error
sources in the LARES 2 experiment, its error budget, Monte Carlo simulations
and covariance analyses confirming an accuracy of a few parts per thousand in
the test of frame-dragging, and we treated the error due to the uncertainty in
the de Sitter effect, a relativistic orbital perturbation. Here we discuss the
impact in the error budget of the LARES 2 frame-dragging experiment of the
orbital perturbation due to thermal drag or thermal thrust. We show that the
thermal drag induces an uncertainty of about one part per thousand in the LARES
2 frame-dragging test, consistent with the error estimates in our previous
papers.Comment: 17 pages, 9 figure
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