The precession of the orbital node of a particle orbiting a rotating mass is known as Lense-Thirring effect (LTE) and is a manifestation of the general relativistic phenomenon of dragging of inertial frames or frame-dragging. The LTE has been measured by using the node drifts of the LAGEOS satellites and GRACE-based Earth gravity field models with an accuracy of about 10% in the recent years. With the LARES experiment launched in 2012 an improvement down to a few percent is anticipated.

A new in-house LAGEOS analysis incorporating a suite of recent gravity field models confirms the 10% level. An example graphical representation of the combination of LAGEOS and LAGEOS-2 data over the years 2000-2016 based on the EIGEN-GRACE03S gravity field is given here. The green line shows the LTE node drift, a regression reveals 46.6 mas/a (milliarcseconds per year) versus a theoretical value of 48.2 mas/a, so a deviation from the prediction by 3%. The red dots show the observed node differences every seven days, eventually being accumulated to yield the green line.

We also investigated the potential of GALILEO to contribute in testing the LTE. It turned out that the solar radiation pressure effects will most likely hide the LTE, however with some proper knowledge of the satellite surface properties and by averaging over the full constellation and by a proper tuning of the POD there remains a chance though. So we will keep up our interest into this for the GALILEO operational phase.