On the use of Ajisai and Jason-1 satellites for tests of General Relativity

In this paper we analyze in detail some aspects of the proposed use of Ajisai and Jason-1, together with the LAGEOS satellites, in order to measure the general relativistic Lense-Thirring effect in the gravitational field of the Earth. A suitably designed linear combination of the nodes of such satellites which cancels out, by construction, the first three even zonal harmonics of the Newtonian multipolar expansion of the terrestrial gravitational potential along with their temporal variations is the observable proposed. It turns out that the systematic error due to the mismodelling in the uncancelled even zonal harmonics would be ∼ 1% according to the latest present-day Earth gravity models which combine data from CHAMP, GRACE and ground-based measurements. In regard to the non-gravitational perturbations especially affecting Jason-1, only relatively high-frequency harmonic perturbations would occur: neither semisecular nor secular bias of nongravitational origin would affect the proposed combination. This is a very important feature because they could be averaged out or fitted and removed from the time series over an observational temporal interval of just some years.