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Lorenzo Iorio

Publications and source records attributed to Lorenzo Iorio.

At least 271 records · Page 15Linked to original sources
arXiv2003

New proposals for the detection of the Earth's gravitomagnetic field in space-based and laboratory-based experiments

In this contribution we present two new proposals for measuring the general relativistic gravitomagnetic component of the gravitational field of the Earth. One proposal consists of the measurement of the difference of the rates of the perigee $ψ$ from the analysis of the laser--ranged data of two identical Earth'artificial satellites placed in equal orbits with supplementary inclinations. In this way the impact of the aliasing classical secular precessions due to the even zonal harmonics of the geopotential would be canceled out, although the non--gravitational perturbations, to which the perigees of LAGEOS--type satellites are particularly sensitive, should be a limiting factor in the obtainable accuracy. With a suitable choice of the inclinations of the orbital planes it would be possible to reduce the periods of such insidious perturbations so to use not too long observational time spans. However, the use of a pair of drag--free satellites would greatly reduce this problem, provided that the time span of the data analysis does not excess the lifetime of the drag--free apparatus. In the other proposal the difference of the rotational periods of two counter-revolving particles placed on a friction-free plane in a vacuum chamber at the South Pole should be measured in order to extract the relativistic gravitomagnetic signal. Among other very challenging practical implications, the Earth's angular velocity $ω_{\oplus}$ should be known at a $10^{-15}$ rad s$^{-1}$ level from VLBI and the friction force of the plane should be less than $2\times 10^{-9}$ dyne.

gr-qc↗
arXiv2003

The impact of the new CHAMP and GRACE Earth gravity models on the measurement of the general relativistic Lense--Thirring effect with the LAGEOS and LAGEOS II satellites

Among the effects predicted by the General Theory of Relativity for the orbital motion of a test particle, the post-Newtonian gravitomagnetic Lense-Thirring effect is very interesting and, up to now, there is not yet an undisputable experimental direct test of it. To date, the data analysis of the orbits of the existing geodetic LAGEOS and LAGEOS II satellites has yielded a test of the Lense-Thirring effect with a claimed accuracy of 20%-30%. According to some scientists such estimates could be optimistic. Here we wish to discuss the improvements obtainable in this measurement, in terms of reliability of the evaluation of the systematic error and reduction of its magnitude, due to the new CHAMP and GRACE Earth gravity models.

gr-qc↗
arXiv2003

Testing General Relativity with Satellite Laser Ranging: Recent Developments

In this paper the most recent developments in testing General Relativity in the gravitational field of the Earth with the technique of Satellite Laser Ranging are presented. In particular, we concentrate our attention on some gravitoelectric and gravitomagnetic post--Newtonian orbital effects on the motion of a test body in the external field of a central mass.

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arXiv2003

On the possibility of testing the Weak Equivalence Principle with artificial Earth satellites

In this paper we examine the possibility of testing the equivalence principle, in its weak form, by analyzing the orbital motion of a pair of artificial satellites of different composition moving along orbits of identical shape and size in the gravitational field of Earth. It turns out that the obtainable level of accuracy is, realistically, of the order of 10^-10 or slightly better. It is limited mainly by the fact that, due to the unavoidable orbital injection errors, it would not be possible to insert the satellites in orbits with exactly the same radius and that such difference could be known only with a finite precision. The present-day level of accuracy, obtained with torsion balance Earth-based measurements and the analysis of Earth-Moon motion in the gravitational field of Sun with the Lunar Laser Ranging technique, is of the order of 10^-13. The proposed space-based missions STEP, \muSCOPE, GG and SEE aim to reach a 10^-15-10^-18 precision level.

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arXiv2003

New perspectives in testing the general relativistic Lense--Thirring effect

Testing the effects predicted by the General Theory of Relativity, in its linearized weak field and slow motion approximation, in the Solar System is difficult because they are very small. Among them the post-Newtonian gravitomagnetic Lense-Thirring effect, or dragging of the inertial frames, on the orbital motion of a test particle is very interesting and, up to now, there is not yet an undisputable experimental direct test of it. Here we illustrate how it could be possible to measure it with an accuracy of the order of 1%, together with other tests of Special Relativity and post-Newtonian gravity, with a joint space based OPTIS/LARES mission in the gravitational field of Earth. Up to now, the data analysis of the orbits of the existing geodetic LAGEOS and LAGEOS II satellites has yielded a test of the Lense-Thirring effect with a claimed accuracy of 20%-30%.

gr-qc↗
arXiv2003

On the possibility of measuring the Earth's gravitomagnetic force in a new laboratory experiment

In this paper we propose, in a preliminary way, a new Earth-based laboratory experiment aimed to the detection of the gravitomagnetic field of the Earth. It consists of the measurement of the difference of the circular frequencies of two rotators moving along identical circular paths, but in opposite directions, on a horizontal friction-free plane in a vacuum chamber placed at South Pole. The accuracy of our knowledge of the Earth's rotation from VLBI and the possibility of measuring the rotators'periods over many revolutions should allow for the feasibility of the proposed experiment.

gr-qc↗
arXiv2003

Light deflection and time delay in the gravitational field of a spinning mass

In this paper we consider the possibility of measuring the corrections induced by the square of the parameter a_g of the Kerr metric to the general relativistic deflection of electromagnetic waves and time delay in an Earth based experiment. It turns out that, while at astronomical scale the well known gravitoelectric effects are far larger than the gravitomagnetic ones, at laboratory scale the situation is reversed: the gravitomagnetic effects exceed definitely the gravitoelectric ones which are totally negligible. By using a small rapidly rotating sphere as gravitating source on the Earth the deflection of a grazing light ray amounts to 10^{-13} rad and the time delay is proportional to 10^{-23} s. These figures are determined by the upper limit in the attainable values of a_g due to the need of preventing the body from exploding under the action of the centrifugal forces. Possible criticisms to the use of the Kerr metric at a_g^2 level are discussed.

gr-qc↗
arXiv2003

A reassessment of the systematic gravitational error in the LARES mission

In this letter we reexamine the evaluation of \zone in some proposed tests of relativistic gravitomagnetism with existing and proposed laser--ranged LAGEOS--like satellites in the gravitational field of the Earth. A more conservative and realistic approach is followed by using the diagonal part only of the covariance matrix of the EGM96 Earth's gravity model up to degree l=20. It turns out that, within this context and according to the present level of knowledge of the terrestrial gravitational field, the best choice would be the use of a recently proposed combination using the nodes Ωof LAGEOS, LAGEOS II and LARES and the perigees ωof LAGEOS II and LARES. Indeed, it turns out to be insensitive both to the even zonal harmonics of degree higher than l=20 and to the correlation among them

gr-qc↗
arXiv2002

A new proposal for measuring the Lense-Thirring effect with a pair of supplementary satellites in the gravitational field of the Earth

In this letter we further analyze the concept of the use of a pair of identical geodetic satellites placed in identical orbits except for the inclinations which should be supplementary for measuring the Lense-Thirring effect in the terrestrial gravitational field. It turns out that not only the sum of the nodes, as already proposed for the LAGEOS-LARES mission, but also the difference of the perigees could be fruitfully adopted.

gr-qc↗
arXiv2002

Is it possible to improve the present LAGEOS-LAGEOS II Lense-Thirring experiment?

The Lense-Thirring effect is currently being measured by means of a combination of the orbital residuals of the nodes of LAGEOS and LAGEOS II and the perigee of LAGEOS II. The total error is of the order of 20%. The most insidious systematic error is due to the mismodelled even zonal harmonics of the geopotential and amounts to 12.9%, according to EGM96 model. The role and the importance of the LAGEOS--LAGEOS II Lense--Thirring experiment is investigated. Using other suitable combinations with orbital elements of the other existing laser-ranged satellites does not yield significative improvements except for one combination including the nodes of LAGEOS, LAGEOS II and Ajisai and the perigee of LAGEOS II. The related systematic error due to the mismodelled even zonal part of the geopotential reduces to almost 10.7%.

gr-qc↗
arXiv2002

The impact of the static part of the Earth's gravity field on some tests of General Relativity with Satellite Laser Ranging

In this paper we calculate explicitly the secular classical precessions of the node Ωand the perigee ωof an Earth artificial satellite induced by the static, even zonal harmonics of the geopotential up to degree l=20. Subsequently, their systematic errors induced by the mismodelling in the even zonal geopotential coefficients J_l are compared to the general relativistic secular gravitomagnetic and gravitoelectric precessions of the node and the perigee of the existing laser-ranged geodetic satellites and of the proposed LARES.

gr-qc↗
arXiv2002

On some gravitomagnetic spin-spin effects for astronomical bodies

In this paper we look at the gravitational spin--spin interaction between macroscopic astronomical bodies. In particular, we calculate their post--Newtonian orbital effects of order $\mathcal{O}(c^{-2})$ on the trajectory of a spinning particle with proper angular momentum ${\bf s}$ moving in the external gravitomagnetic field generated by a central spinning mass with proper angular momentum ${\bf J}$. It turns out that, at order $\mathcal{O}(e)$ in the orbiter's eccentricity, the eccentricity the pericenter and the mean anomaly rates of the moving particle are affected by long--term harmonic effects. If, on one hand, they are undetectable in the Solar System, on the other, maybe that in an astrophysical context like that of the binary millisecond pulsars there will be some hopes of measuring them in the future.

gr-qc↗
arXiv2002

A critical approach to the concept of a polar, low-altitude LARES satellite

According to very recent developments of the LARES mission, which would be devoted to the measurement of the general relativistic Lense--Thirring effect in the gravitational field of the Earth with Satellite Laser Ranging, it seems that the LARES satellite might be finally launched in a polar, low--altitude orbit by means of a relatively low--cost rocket. The observable would be the node only. In this letter we critically analyze this scenario.

gr-qc↗
arXiv2002

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 $10^{\rm -3}$. 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 $\et=4β-γ-3$ from Lunar Laser Ranging it could be possible to obtain an estimate of the PPN parameters $γ$ and $β$ at the $10^{-2}-10^{-3}$ level.

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