Optimal orbits for temporal gravity recovery regarding temporal aliasing

Murböck, Michael; Pail, Roland; Daras, Ilias; Gruber, Thomas

doi:10.1007/s00190-013-0671-y

Cited by 21 publications

(12 citation statements)

References 16 publications

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“…The simulations presented in this study have been conducted on IAPG's closed-loop reducedscale simulation software which is described in detail in Murböck (2015) and Murböck et al (2014). Compared to a real gravity mission processing scheme this tool uses various simplifications as a trade-off for improved computation time.…”

Section: Simulation Environment and Parametersmentioning

confidence: 99%

Impact of a novel hybrid accelerometer on satellite gravimetry performance

Abrykosov

Pail

Gruber

et al. 2019

Advances in Space Research

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The state-of-the-art electrostatic accelerometers (EA) used for the retrieval of nongravitational forces acting on a satellite constitute a core component of every dedicated gravity field mission. However, due to their difficult-to-control thermal drift in the low observation frequencies, they are also one of the most limiting factors of the achievable performance of gravity recovery. Recently, a hybrid accelerometer consisting of a regular EA and a novel cold atom interferometer (CAI) that features a time-invariant observation stability and constantly recalibrates the EA has been developed in order to remedy this major drawback. In this paper we aim to assess the value of the hybrid accelerometer for gravity field retrieval in the context of GRACE-type and Bender-type missions by means of numerical closed-loop simulations where possible noise specifications of the novel instrument are considered and different components of the Earth's gravity field signal are added subsequently. It is shown that the quality of the gravity field solutions is mainly dependent on the CAI's measurement accuracy. While a low CAI performance (10-8 to 10-9 m/s 2 /Hz 1/2) does not lead to any gains compared to a stand-alone EA, a sufficiently high one (10-11 m/s 2 /Hz 1/2) may improve the retrieval performance by over one order of magnitude. We also show that improvements which are limited to low-frequency observations may even propagate into high spherical harmonic degrees. Further, the accelerometer performance seems to play a less prominent role if the overall observation geometry is improved as it is the case for a Bender-type mission. The impact of the accelerometer measurements diminishes further when temporal variations of the gravity field are introduced, pointing out the need for proper de-aliasing techniques. An additional study reveals that the hybrid accelerometer is-contrary to a stand-alone EA-widely unaffected by scale factor instabilities.

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Section: Simulation Environment and Parametersmentioning

confidence: 99%

Impact of a novel hybrid accelerometer on satellite gravimetry performance

Abrykosov

Pail

Gruber

et al. 2019

Advances in Space Research

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“…Correspondingly, the science and user needs of NGGMs were defined in [4]. In several previous studies, different mission concepts have been studied in detail, with emphasis on orbit design and resulting spatial-temporal ground track pattern, enhanced processing and parameterization strategies, and improved post-processing/filtering strategies in order to reduce temporal aliasing effects, which are one of the main error sources of current temporal gravity field solutions [5]. The typical GRACE-type concept of two satellites (satellite pair) following each other on the same orbit with an inter-satellite distance of about 200 km observes only the along-track component of the Earth's gravity field, and therefore leads to a very anisotropic error structure and the typical striping patterns in the resulting temporal gravity solutions.…”

Section: Introductionmentioning

confidence: 99%

Next-Generation Gravity Missions: Sino-European Numerical Simulation Comparison Exercise

et al. 2019

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Temporal gravity retrieval simulation results of a future Bender-type double pair mission concept, performed by five processing centers of a Sino-European study team, have been inter-compared and assessed. They were computed in a synthetic closed-loop simulation world by five independent software systems applying different gravity retrieval methods, but were based on jointly defined mission scenarios. The inter-comparison showed that the results achieved a quite similar performance. Exemplarily, the root mean square (RMS) deviations of global equivalent water height fields from their true reference, resolved up to degree and order 30 of a 9-day solution, vary in the order of 10% of the target signal. Also, co-estimated independent daily gravity fields up to degree and order 15, which have been co-estimated by all processing centers, do not show large differences among each other. This positive result is an important pre-requisite and basis for future joint activities towards the realization of next-generation gravity missions.

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“…To analyze the effect of deterministic error sources like ocean tide (OT) signal, an OT difference signal is added to the observations, leading to the residual SH degree RMS drawn in the dashed lines. As described in [18], characteristic RMS peaks, induced by incomplete OT de-aliasing affecting specific SH order bands, can be seen in the dashed gray line around SH degrees 46, 61, and 107. As one can conclude from the dashed red line, the OT signal is almost completely removed from the observations and the residuals are almost as small as for the case without deterministic errors.…”

Section: Determination Of a Favorable Filter Designmentioning

confidence: 75%

“…In order to perform the closed-loop simulations, we employ the closed-loop mission simulator described by [18] to simulate GRACE-like observations and to calculate monthly GRACE-like time variable gravity field solutions. Acceleration differences along the line of sight between the two satellites serve as observations.…”

Section: The Closed-loop Simulation Environmentmentioning

confidence: 99%

Decorrelation of GRACE Time Variable Gravity Field Solutions Using Full Covariance Information

et al. 2018

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In this study the feasibility and performance of time variable decorrelation (VADER) filters derived from covariance information on decadal Gravity Recovery and Climate Experiment (GRACE) time series are investigated. The VADER filter is based on publicly available data that are provided by several GRACE processing centers, and does not need its own Level-2 processing chain. Numerical closed loop simulations, incorporating stochastic and deterministic error budgets, serve as basis for the design of the filter setup, and the resulting filters are subsequently applied for real data processing. The closed loop experiments demonstrate the impact of temporally varying error and signal covariance matrices that are used for the design of decorrelation filters. The results indicate an average reduction of cumulative geoid height errors of 15% using time-variable instead of static decorrelation. Based on the simulation experience, a real data filtering procedure is designed and set up. It is applied to the ITSG-Grace2014 time variable gravity field time series with its associated full monthly covariance matrices. To assess the validity of the approach, linear mass trend estimates for the Antarctic Peninsula are computed using VADER filters and compared to previous estimates from both, GRACE and other mass balance estimation techniques. The mass change results obtained show very good agreement with other estimates and are robust against variations of the filter strength. The DDK decorrelation filter serves as main benchmark for the assessment of the VADER filter. For comparable filter strengths the VADER filters achieve a better de-striping and deliver smaller formal errors than static filters like the DDK.

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Optimal orbits for temporal gravity recovery regarding temporal aliasing

Cited by 21 publications

References 16 publications

Impact of a novel hybrid accelerometer on satellite gravimetry performance

Impact of a novel hybrid accelerometer on satellite gravimetry performance

Next-Generation Gravity Missions: Sino-European Numerical Simulation Comparison Exercise

Decorrelation of GRACE Time Variable Gravity Field Solutions Using Full Covariance Information

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