Collinearity assessment of SLR-derived geocentre coordinates

Abstract:

Satellite laser ranging (SLR) is acknowledged to be the state-of-the-art geodetic technique for determining geocentre motion, defined as the differential motion of the centre of mass of the whole Earth system relative to the centre of the solid Earth’s surface figure. Geocentre motion is induced by mass redistribution occurring in the Earth system and can potentially affect the interpretation of global scale geophysical processes such as present-day mass transport, sea level rise and glacial isostatic adjustment. At present, the International Terrestrial Reference Frame (ITRF) origin is defined only by SLR observations to the LAGEOS-1 and 2 satellites. The accuracy and stability of the origin are approximately a factor of two lower for the Z component compared to the equatorial components. Despite their long observational history and high data yields, the low Earth orbit (LEO) geodetic satellites Starlette, Stella and Ajisai are ignored mostly due to the more complicated modelling of non-gravitational forces, particularly atmospheric drag, acting on their surfaces. By means of collinearity diagnosis, we assess the current capability of SLR to sense geocentre motion via the network shift approach using real ground networks and LAGEOS-1 and 2 observations. We show that the combined processing of LAGEOS and LEO satellite data reduces the collinearity issues of the Z geocentre coordinate under certain solution parameterisations. The frequent estimation of drag coefficients can, however, severely amplify the collinearity problems for all components.