On the capability to derive mass estimates from high-low satellite-to-satellite tracking data

Poster (2013, December)

Recently it has been shown that it is possible to derive time-variable gravity signals from high-low satellite-to-satellite tracking (hl-SST) missions (Weigelt et al. 2013, JGR:Solid Earth, doi:10.1002 ... [more ▼]

Recently it has been shown that it is possible to derive time-variable gravity signals from high-low satellite-to-satellite tracking (hl-SST) missions (Weigelt et al. 2013, JGR:Solid Earth, doi:10.1002/jgrb.50283). Based on the GPS information only, we will present results derived from the dedicated gravity field missions CHAMP, GRACE and GOCE which allow us to determine mass estimates for various applications. Hydrologically induced mass changes on land cause the strongest mass variations in the gravity field and can be easily identified in the hl-SST data, especially in areas with strong signals such as the Amazon basin. Ice melt in Greenland can be derived from the data and mass estimates compare well to corresponding GRACE estimates. Also, loading time series based on these gravity field solutions agree well with GPS observations for various stations around the globe. We also discuss the limitations of the data, e.g. in detecting signals related to glacial isostatic adjustment or earthquake-induced gravity field changes. Overall, we will demonstrate that the quality of the GPS data is sufficient nowadays and with a proper processing strategy it is possible to derive reasonable mass estimates. As such, this type of observations may allow to bridge a possible gap between GRACE and its successor GRACE Follow-On scheduled for launch in 2017. [less ▲]

On the capability of non-dedicated GPS-tracked satellite constellations for estimating mass variations: case study SWARM

Scientific Conference (2013, September)

Hydrological mass changes inferred from high-low satellite-to-satellite tracking data

Scientific Conference (2013, April)

The technique of deriving time variable gravity (TVG) field observations from high-low satellite-to-satellite tracking (hl-SST) is beginning to establish itself as a valuable and supplementary source for ... [more ▼]

The technique of deriving time variable gravity (TVG) field observations from high-low satellite-to-satellite tracking (hl-SST) is beginning to establish itself as a valuable and supplementary source for the determination and description of long wavelength geophysical phenomena. Recent developments in data processing techniques have pushed the limits of the accuracy of these types of observations and now allows for realistic determinations of long-term trends and annual amplitudes of hydrological signals. We use CHAMP data and a dedicated signal processing to derive annual and inter-annual variations in the largest catchments of the Earth system, e.g. Amazon, Ob and Lena. Results are validated by computing the correlation of aggregated water storage changes from CHAMP (and GRACE) with the hydro-meteorological storage changes. High noise levels demand a stronger filtering, e.g. larger filtering radius (1000-1400km), than usually applied in case of GRACE. We therefore also investigate the effect of filtering on the consistency with the hydrological mass changes and estimate the signal to noise ratio and the spatial and temporal dependency of the noise. We will show that hl-SST observations are a viable source of information for TVG which can even serve as a reliable substitute in the event of the impending end of GRACE's active lifetime. [less ▲]

Time variability from high-low SST - filling the gap between GRACE and GFO

Scientific Conference (2012, October)

Large scale time variability from high-low SST - filling the gap between GRACE and GFO

Scientific Conference (2012, September)

GOCE long-wavelength gravity field recovery from high-low satellite-to-satellite-tracking using the acceleration approach

Poster (2012, April)

Assessment of aliasing effect of white noise on different solutions in gravity recovery simulations of a GRACE-like mission

Scientific Conference (2011, July)

Comparison of full-repeat and sub-cycle solutions in gravity recovery simulations of a GRACE-like mission

Scientific Conference (2011, April)

Long wavelength gravity field determination from GOCE using the acceleration approach

Poster (2011, April)

Spaceborne Gravimetric Satellite Constellations and Ocean Tides: aliasing effects

in Geophysical Journal International (2010), (181), 789-805

Ocean tides redistribute mass at high temporal frequencies. Satellite missions that aim to observe medium to low frequency mass variations need to take into account this rapidly varying mass signal ... [more ▼]

Ocean tides redistribute mass at high temporal frequencies. Satellite missions that aim to observe medium to low frequency mass variations need to take into account this rapidly varying mass signal. Correcting for the effects of ocean tides by means of imperfect models might hamper the observation of other temporal gravity field signals of interest. This paper explores different methods for mitigating aliasing errors for the specific example of observing mass variations due to land hydrology, including temporal filtering of time-series of gravity solutions, spatial smoothing and the use of satellite constellations. For this purpose, an Earth System Model (ESM) was constructed, which included state-of-the-art time varying components for ocean, atmosphere, solid Earth, hydrology, ice-sheets and ocean tides. Using the ESM, we simulated the retrieval of the hydrologically driven gravity field changes using a number of different satellite constellations. We find that (1) the ocean tide aliasing strongly depends on the satellite constellation, the choice of orbital parameters and the length of the data span; (2) the aliasing effect manifests itself differently for different geographical regions; (3) the aliasing causes a peculiar striping pattern along the ground track of the satellite orbits; (4) optimizing the choice of orbital parameters of a single GRACE-type tandem can be more effective at reducing the aliasing of ocean tide model errors than flying more tandems. Finally, we corroborate the experiences with GRACE data analysis that appropriate post-processing techniques can significantly improve the quality of the retrieved gravity changes. [less ▲]