How to reach a few percent level in determining the Lense-Thirring effect?

In this paper we discuss and compare a node-only LAGEOS-LAGEOS II combination and a node-only LAGEOS-LAGEOS II-Ajisai-Jason1 combination for the determination of the Lense-Thirring effect. The new combined EIGEN-CG01C Earth gravity model has been adopted. The second combination cancels the first three even zonal harmonics along with their secular variations but introduces the non-gravitational perturbations of Jason1. The first combination is less sensitive to the non-conservative forces but is sensitive to the secular variations of the uncancelled even zonal harmonics of low degree J4 and J6 whose impact grows linearly in time.Comment: Latex2e, 22 pag. 1 table, 2 figures, 45 references. Changes in the Abstract, Introduction and Conclusions. Discussion on the non-gravitational perturbations on Ajisai and on the impact of the secular rates of the even zonal harmonics added. EIGEN-CG01C CHAMP+GRACE+terrestrial gravimetry/altimetry Earth gravity model used. Reference adde

Understanding ice-sheet mass balance: progress in satellite altimetry and gravimetry

Satellite remote sensing has come to dominate the measurement of glacier and ice-sheet change. Three independent methods now exist for assessing ice-sheet mass balance and we focus on progress in two: satellite altimetry (ICESat) and gravimetry (GRACE). With improved spatial and temporal sampling, and synergy with ice flow measurements, both the mechanisms and causes changing mass balance can be investigated. We present examples of mass losses due to widespread, intensifying glacier dynamic thinning in northwest Greenland, but local ablation rates in the northeast that are unchanged for decades. Advances in GRACE processing reveal Greenland net ice-sheet mass loss continuing into 2010, at 19530 Gt a–1. A similarly negative trend in the Gulf of Alaska has significant spatial and temporal variation, that highlights the importance of intense summer melting here. Strong summer melt on the Antarctic Peninsula also precipitated recent ice-shelf collapse and prompted rapid dynamic thinning of tributary glaciers at up to 70ma–1. Thinning continued for years to decades after collapse and propagated far inland. While understanding of the physical mechanisms of change continues to improve, estimates of future behaviour, and in particular the near-future glacial sea-level contribution, still rely on projections from such observations.We introduce the suite of new sensors that will monitor the ice sheets into the future

Towards development of a consistent orbit series for TOPEX, Jason-1, and Jason-2

International audienc