G03 Variations of the Gravity Field

IAG (Geodesy)



24-Jun-2015, 13:30 - 15:00


 
Abstract content:

Time-variable gravity field from SLR and combined GRACE-SLR solutions

GRACE satellites provide substantial information about the temporal variability of the gravity field at long to medium wavelengths describing the mass transport in the system Earth. The GRACE solutions suffer, however, from the poor determination of the Earth’s oblateness from GRACE K-Band data, due to the aliasing with the S2 tide. On the other hand, the Earth’s oblateness and its temporal variability can be very well determined using the Satellite Laser Ranges (SLR) to spherical geodetic satellites, e.g., LAGEOS, Starlette, Stella, Ajisai, and LARES. We perform a combination of GRACE and SLR solutions at the normal equation level using the SLR monthly gravity fields from the combined analysis of up to 9 SLR geodetic satellites. A reduction of the influence of the S2 tide alias on some GRACE-derived coefficients by using a combination with SLR data will be addressed.

Over the past years, the K-Band tracking between GRACE-A/B satellites was deactivated several times, which caused gaps in the series of GRACE monthly gravity field solutions. The GRACE on-board GPS receivers were, however, active almost continuously and they provided uninterrupted observations. We investigate whether the combined SLR+GRACE GPS-only solutions can fill the gaps of monthly series of gravity field models for the months with none or sparse K-Band observations. Finally, we discuss the temporal variability of the SLR-derived Earth’s gravity field for 1995-2014, thus including the period prior to the GRACE launch. The changes of the trends for selected regions, e.g., Antarctica and Greenland will particularly be addressed.

 
Author(s):
K. Sosnica1, U. Meyer1, A. Maier1, A. Jäggi1.
1Astronomical Institute, University of Bern, Bern, Switzerland.

 

Keywords:
Satellite Laser Ranging     Gravity field     GRACE     Earth's oblateness     Temporal gravity changes     LAGEOS     LARES