What Can be Expected from the GRACE-FO Laser Ranging Interferometer for Earth Science Applications?

Abstract

The primary objective of the Gravity Recovery and Climate Experiment follow-on (GRACE-FO) satellite mission, due for launch in August 2017, is to continue the GRACE time series of global monthly gravity field models. For this, evolved versions of the GRACE microwave instrument (MWI), GPS-receiver, and accelerometer will be used. A secondary objective is to demonstrate the effectiveness of a laser ranging interferometer (LRI) in improving the satellite-to-satellite tracking measurement performance. In order to investigate the expected enhancement for Earth science applications we have performed a full-scale simulation over the nominal mission lifetime of five years using a realistic orbit scenario and error assumptions both for instrument and background model errors.Unfiltered differences between the synthetic input and the finally recovered time-variable monthly gravity models show notable improvements with the LRI, on global scale, of the order of 23%. The gain is realized for wavelengths smaller than 240 km in case of Gaussian filtering but decreases to just a few percent when anisotropic filtering is applied. This is also confirmed for some typical regional Earth science applications which show randomly distributed patterns of small improvements but also degradations when using DDK4 filtered LRI based models.Analysis of applied error models indicates that accelerometer noise followed by ocean tide and non-tidal mass variation errors are the main contributors to the overall GRACE-FO gravity model error. Improvements in these fields are therefore necessary, besides optimized constellations, to make use of the increased LRI accuracy and to significantly improve gravity field models from Next Generation Gravity Missions.

A new high-resolution model of non-tidal atmosphere and ocean mass variability for de-aliasing of satellite gravity observations: AOD1B RL06

“…Quantitative estimates of mass changes obtained from GRACE observations revealed, for example, substantial mass loss in the Tien Shan high-mountain glaciers (Farinotti et al 2015); the non-sustainable depletion of groundwater resources in various densely populated regions of the world (Famiglietti 2014) and a gradually increasing Greenland meltwater discharge which impacts Labrador Sea convection and consequently the meridional overturning circulation in the North Atlantic (Yang et al 2016). The relevance of GRACE for the monitoring of environmental changes is reflected in the approval of the follow-on mission GRACE-FO, which is scheduled for launch in Spring 2018 February (Flechtner et al 2016).…”

On the Applicability of the Geodesic Deviation Equation in General Relativity

“…3 for one reference period and a chosen reference radius of 5000 km above the surface of the Earth. As one would expect, a positive radial perturbation C (1) yields a smaller azimuthal frequency,φ = Ω Φ + δω (1) < Ω Φ , as compared to the reference motion. The frequency and radial perturbations are related via…”

“…The magnitude of the normalized radial perturbation C (i) /R as a function of C (1,2,3) and the reference radius R. The lines represent surfaces of constant C (i) /R. We use a mean Earth radius R ⊕ = 6.37 · 10 3 km.…”

Gravity Gradiometry With GRACE Space Missions: New Opportunities for the Geosciences

“…Thanks to the success of the GRACE mission that exceeded threefold its design life, a nearly identical follow-on mission, namely, the GRACE follow-on (GRACE-FO or GFO), was launched on 22 May 2018. GRACE-FO will continue tracking the Earth's mass movements, particularly water mass storage and transport (Flechtner et al, 2016), providing invaluable information on processes occurring in the Earth system. GOCE mission (2009GOCE mission ( -2013, on the other hand, was a single spacecraft that orbited the Earth at almost half the GRACE altitude that is, at~250 km.…”