Towards a 1% measurement of the LenseThirring effect with LARES?
Abstract
After the recent approval by the Italian Space Agency (ASI) of the LARES mission, which will be launched at the end of 2008 by a VEGA rocket to measure the general relativistic gravitomagnetic LenseThirring effect by combining LARES data with those of the existing LAGEOS and LAGEOS II satellites, it is of the utmost importance to assess if the claimed accuracy ≲ 1 % will be realistically obtainable. A major source of systematic error is the mismodelling δJ_{ℓ} in the static part of the even zonal harmonic coefficients J_{ℓ}, ℓ = 2, 4, 6, .. of the multipolar expansion of the classical part of the terrestrial gravitational potential; such a bias crucially depends on the orbital configuration of LARES. If for δJ_{ℓ} the difference between the best estimates of different Earth's gravity solutions from the dedicated GRACE mission is conservatively taken instead of optimistically considering the statistical covariance sigmas of each model separately, as done so far in literature, it turns out that, since LARES will be likely launched in a loworbit (semimajor axis a ≲ 7600km), the bias due to the geopotential may be up to ten times larger than what claimed, according to a calculation up to degree ℓ = 20 . Taking into account also the even zonal harmonics with ℓ > 20 , as required by the relatively low altitude of LARES, may further degrade the total accuracy. Should a nearly polar configuration (inclination to the Earth's equator i ≈ 90 deg) be finally implemented, also other perturbations would come into play, further corrupting the measurement of the LenseThirring effect. The orbital configuration of LARES may also have some consequences in terms of nongravitational perturbations and measurement errors.
 Publication:

Advances in Space Research
 Pub Date:
 April 2009
 DOI:
 10.1016/j.asr.2008.10.016
 arXiv:
 arXiv:0802.2031
 Bibcode:
 2009AdSpR..43.1148I
 Keywords:

 Experimental tests of gravitational theories;
 Satellite orbits;
 Harmonics of the gravity potential field;
 General Relativity and Quantum Cosmology;
 Astrophysics;
 Physics  Geophysics;
 Physics  Space Physics
 EPrint:
 Latex, 21 pages, 8 figures, 4 tables, 26 references. To appear in Advances in Space Research (ASR)