J2: An evaluation of new estimates from GPS, GRACE, and load models compared to SLR

Changes in J2, resulting from past and present changes in Earth's climate, are traditionally observed by Satellite Laser ranging (SLR). Assuming an elastic Earth, it is possible to infer changes in J2 from changes in Earth's shape observed by GPS. We compare estimates of non-secular J2 changes from GPS, SLR, GRACE, and a load model. The GPS and...

Higher?order ionospheric effects on the GPS reference frame and velocities

We describe how GPS time series are influenced by higher?order ionospheric effects over the last solar cycle (1995–2008) and examine implications for geophysical studies. Using 14 years of globally reprocessed solutions, we demonstrate the effect on the reference frame. Including second? and third?order ionospheric terms causes up to 10 mm...