Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Towards a few-percent measurement of the Lense-Thirring effect with the
  LAGEOS and LAGEOS II satellites?   Up to now attempts to measure the general relativistic Lense-Thirring effect
in the gravitational field of Earth have been performed by analyzing a suitable
J_2-J_4-free combination of the nodes Omega of LAGEOS and LAGEOS II and the
perigee omega of LAGEOS II with the Satellite Laser Ranging technique. The
claimed total accuracy is of the order of 20-30%, but, according to some
scientists, it could be an optimistic estimate. The main sources of systematic
errors are the mismodelling in the even zonal harmonic coefficients J_l of the
multipolar expansion of the gravitational potential of Earth and the
non-gravitational perturbations which plague especially the perigee of LAGEOS
II and whose impact on the proposed measurement is difficult to be reliably
assessed. Here we present some evaluations of the accuracy which could be
reached with a different J_2-free observable built up with the nodes of LAGEOS
and LAGEOS II in view of the new preliminary 2nd-generation Earth gravity
models from the GRACE mission. According to the GRACE-only based EIGEN-GRACE02S
solution, a 1-sigma upper bound of 4% for the systematic error due to the even
zonal harmonics can be obtained. In the near future it could be possible to
perform a reliable measurement of the Lense-Thirring effect by means of the
existing LAGEOS satellites with an accuracy of a few percent by adopting a time
span of a few years. The choice of a not too long observational temporal
interval would be helpful in reducing the impact of the secular variations of
the uncancelled even zonal harmonics dot J_4 and dot J_6 whose impact is
difficult to be reliably evaluated.

27
The categories of this paper are: comp-gas
15
The categories of this paper are: nucl-ex
6
The categories of this paper are: astro-ph
35
The categories of this paper are: mtrl-th
28
The categories of this paper are: alg-geom
29
The categories of this paper are: funct-an
9
The categories of this paper are: nlin
21
The categories of this paper are: adap-org
19
The categories of this paper are: eess
26
The categories of this paper are: bayes-an
24
The categories of this paper are: dg-ga
37
The categories of this paper are: supr-con
32
The categories of this paper are: atom-ph
2
The categories of this paper are: math
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn