Commentary to "LARES successfully launched in orbit: Satellite and mission description" by A. Paolozzi and I. Ciufolini

Abstract

We comment on some statements in a recent paper by Paolozzi and Ciufolini concerning certain remarks raised by us on the realistic accuracy obtainable in testing the general relativistic Lense-Thirring effect in the gravitational field of the Earth with the newly launched LARES satellite together with the LAGEOS and LAGEOS II spacecraft in orbit for a long time. The orbital configuration of LARES is different from that of the originally proposed LAGEOS-3. Indeed, while the latter one should have been launched to the same altitude of LAGEOS (i.e. about $h_{\rm L}=5890$ km) in an orbital plane displaced by $180$ deg with respect to that of LAGEOS ($I_{\rm L}=110$ deg, $I_{\rm L3}=70$ deg), LARES currently moves at a much smaller altitude (about $h_{\rm LR}=1440$ km) and at a slightly different inclination ($I_{\rm LR} = 69.5$ deg). As independently pointed out in the literature by different authors, the overall accuracy of a LARES-LAGEOS-LAGEOS II Lense-Thirring test may be unfavorably \textcolor{black}{impacted} by the lower altitude of LARES with respect to the expected $\approx 1%$ level claimed by Ciufolini \textit{et al.} because of an enhanced sensitivity to the low-degree even zonal geopotential coefficients inducing orbital precessions competing with the relativistic ones. Concerning the previous tests performed with the combined nodes of only LAGEOS and LAGEOS II, an independent analysis recently appeared in the literature indirectly confirms that the total uncertainty in them is likely far from being as little as $10%$.