0 40 41 07 v 1 2 6 A pr 2 00 4 On the impossibility of using the longitude of the ascending node of GP - B for measur - ing the Lense - Thirring effect

The possibility of analyzing the node Ω of the GP-B satellite in order to measure also the Lense-Thirring effect on its orbit is examined. This feature is induced by the general relativistic gravitomagnetic component of the Earth gravitational field. The GP-B mission has been launched in April 2004 and is aimed mainly to the measurement of the gravitomagnetic precession of four gyroscopes carried onboard at a claimed accuracy of 1%. The aliasing effect of the solid Earth and ocean components of the solar K1 tidal perturbations would make the measurement of the Lense–Thirring effect on the orbit unfeasible. Indeed, the science period of the GP-B mission amounts to almost one year. During this time span the Lense-Thirring shift on the GP-B node would be 164 milliarcseconds (mas), while the tidal perturbations on its node would have a period of the order of 10 years and amplitudes of the order of 10 mas.