Constellations and formations of small satellites in NGGM concepts

Mapping Intimacies ◽

10.5194/gstm2020-44 ◽

2020 ◽

Author(s):

Nikolas Pfaffenzeller ◽

Roland Pail

Keyword(s):

Gravity Field ◽

Cost Effective ◽

Transport Processes ◽

Ocean Tide ◽

Satellite Mission ◽

Spatiotemporal Resolution ◽

Small Satellites ◽

Gravity Fields ◽

Ocean Tide Models ◽

Temporal Gravity

In the context of an increased public interest in climate-relevant processes, a number of studies on Next Generation Gravity Missions (NGGMs) have been commissioned to better map mass transport processes on Earth. On the basis of the successfully completed gravity field missions CHAMP, GOCE and GRACE as well as the current satellite mission GRACE-FO, different concepts were examined for their feasibility and economic efficiency. The focus is on increasing the spatiotemporal resolution while simultaneously reducing the known error effects such as the aliasing of temporal gravity fields due to under-sampling of signals and uncertainties in ocean tide models. An additional inclined pair to a GRACE-like satellite pair (Bender constellation) is the most promising solution. Since the costs for a realization of the Bender constellation are very high, this contribution focuses on alternative concepts in the form of different constellations and formations of small satellites. The latter includes both satellite pairs and chains consisting of trailing satellites. The aim is to provide a cost-effective alternative to the previous gravity field satellites while simultaneously increasing the spatiotemporal resolution and minimizing the above mentioned error effects. In numerical closed-loop simulations, various scenarios will be conducted which differ in orbit parameters like shape and number of orbits and the number of satellites per orbit and instrument performances. Additionally, the impacts from the co-parametrization of non-tidal short periodic temporal gravity field signal on the gravity field solutions (so-called Wiese approach), obtained by the different concepts, will be investigated. In particular the possibilities and limits with multiple satellites pairs for achieving the highest possible spatial and temporal resolution in (sub-)daily temporal gravity fields shall be analyzed in detail which is crucial for macrosocial tasks in water balance estimation and water management.

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Simulation study on gravity field determination with small satellites in NGGM

10.5194/egusphere-egu21-5341 ◽

2021 ◽

Author(s):

Nikolas Pfaffenzeller ◽

Roland Pail

Keyword(s):

Gravity Field ◽

Cost Effective ◽

Transport Processes ◽

Ocean Tide ◽

Satellite Mission ◽

Spatiotemporal Resolution ◽

Small Satellites ◽

Gravity Fields ◽

Ocean Tide Models ◽

Temporal Gravity

In the context of an increased public interest in climate-relevant processes, a number of studies on Next Generation Gravity Missions (NGGMs) have been commissioned to better map mass transport processes on Earth. On the basis of the successfully completed gravity field missions CHAMP, GOCE and GRACE as well as the current satellite mission GRACE-FO, different concepts were examined for their feasibility and economic efficiency. The focus is on increasing the spatiotemporal resolution while simultaneously reducing the known error effects such as the aliasing of temporal gravity fields due to under-sampling of signals and uncertainties in ocean tide models. An additional inclined pair to a GRACE-like satellite pair (Bender constellation) is the most promising solution. Since the costs for a realization of the Bender constellation are very high, this contribution focuses on alternative concepts in the form of different constellations and formations of small satellites. The latter includes both satellite pairs and chains consisting of trailing satellites. The aim is to provide a cost-effective alternative to the previous gravity field satellites while simultaneously increasing the spatiotemporal resolution and minimizing the above mentioned error effects. In numerical closed-loop simulations, various scenarios will be conducted which differ in orbit parameters like shape and number of orbits, the number of satellites per orbit and instrument performances. Additionally, the impacts from the co-parametrization of non-tidal temporal gravity field signal and ocean tides on the gravity field solutions, obtained by the different concepts, will be investigated. In particular the possibilities and limits with multiple satellites pairs for achieving the highest possible spatial and temporal resolution in (sub-)daily temporal gravity fields shall be analysed in detail.

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Simulation study on future gravity missions with constellations and formations of small satellites

10.5194/egusphere-egu2020-10103 ◽

2020 ◽

Author(s):

Nikolas Pfaffenzeller ◽

Roland Pail ◽

Tom Yunck

Keyword(s):

Gravity Field ◽

Cost Effective ◽

Transport Processes ◽

Ocean Tide ◽

Satellite Mission ◽

Spatiotemporal Resolution ◽

Small Satellites ◽

Under Sampling ◽

Ocean Tide Models ◽

Temporal Gravity

In the context of an increased public interest in climate-relevant processes, a number of studies on Next Generation Gravity Missions (NGGMs) have been commissioned to better map mass transport processes on Earth. On the basis of the successfully completed gravity field missions CHAMP, GOCE and GRACE as well as the current satellite mission GRACE-FO, different concepts were examined for their feasibility and economic efficiency. The focus is on increasing the spatiotemporal resolution while simultaneously reducing the known error effects such as the aliasing of temporal gravity fields due to under-sampling of signals and uncertainties in ocean tide models. An additional inclined pair to a GRACE-like satellite pair (Bender constellation) is the most promising solution. Since the costs for a realization of the Bender constellation are very high, this contribution focuses on alternative concepts in the form of different constellations and formations of small satellites. The latter includes both satellite pairs and chains consisting of trailing satellites. The aim is to provide a cost-effective alternative to the previous gravity field satellites while simultaneously increasing the spatiotemporal resolution and minimizing the above mentioned error effects. In numerical closed-loop simulations, different scenarios will be performed which differ in orbit parameters like shape and number of orbits, the number of satellites per orbit and their distance to each other as well as the number of inter-satellite links. Additionally, the impacts from the co-parametrization of non-tidal temporal gravity field signal and ocean tides on the gravity field solutions, obtained by the different concepts, will be investigated.&#160;

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MATLAB tools for the post-processing of GRACE temporal gravity field solutions

10.5194/egusphere-egu2020-2479 ◽

2020 ◽

Author(s):

Dimitrios Piretzidis ◽

Michael Sideris

Keyword(s):

Gravity Field ◽

Land Surface ◽

Optimal Strategies ◽

Post Processing ◽

Satellite Mission ◽

Surface Mass ◽

Isostatic Adjustment ◽

Processing Strategies ◽

Grace Data ◽

Temporal Gravity

We present a collection of MATLAB tools for the post-processing of temporal gravity field solutions from the Gravity Recovery and Climate Experiment (GRACE) satellite mission. GRACE final products are in the form of monthly sets of spherical harmonic coefficients and have been extensively used by the scientific community to study the land surface mass redistribution that is predominantly due to ice melting, glacial isostatic adjustment, seismic activity and hydrological phenomena. Since the launch of GRACE satellites, a substantial effort has been made to develop processing strategies and improve the surface mass change estimates.The MATAB software presented in this work is developed and used by the Gravity and Earth Observation group at the department of Geomatics Engineering, University of Calgary. A variety of techniques and tools for the processing of GRACE data are implemented, tested and analyzed. Some of the software capabilities are: filtering of GRACE data using decorrelation and smoothing techniques, conversion of gravity changes into mass changes on the Earth&#8217;s spherical, ellipsoidal and topographical surface, implementation of forward modeling techniques for the estimation and removal of long-term trends due to ice mass melting, basin-specific spatial averaging in the spatial and spectral domain, time series smoothing and decomposition techniques, and data visualization.All tools use different levels of parameterization in order to assist both expert users and non-specialists. Such a software makes the comparison between different GRACE processing methods and parameters used easier, leading to optimal strategies for the estimation of surface mass changes and to the standardization of GRACE data post-processing. It could also facilitate the use of GRACE data to non-geodesists.

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Applicability of GRACE and GRACE-FO for monitoring water mass changes of the Aral Sea and the Caspian Sea

Proceedings of the International conference “InterCarto/InterGIS” ◽

10.35595/2414-9179-2020-2-26-443-453 ◽

2020 ◽

Vol 26 (2) ◽

pp. 443-453

Author(s):

Lorant Földváry ◽

Victor Statov ◽

Nizamatdin Mamutov

Keyword(s):

Gravity Field ◽

Caspian Sea ◽

Large Scale ◽

Aral Sea ◽

Water Volume ◽

Satellite Mission ◽

The Caspian Sea ◽

Gravity Fields ◽

Range Rate ◽

Sea Area

The GRACE gravity satellite mission has provided monthly gravity field solutions for about 15 years enabling a unique opportunity to monitor large scale mass variation processes. By the end of the GRACE, the GRACE-FO mission was launched in order to continue the time series of monthly gravity fields. The two missions are similar in most aspects apart from the improved intersatellite range rate measurements, which is performed with lasers in addition to microwaves. An obvious demand for the geoscientific applications of the monthly gravity field models is to understand the consistency of the models provided by the two missions. This study provides a case-study related consistency investigation of GRACE and GRACE-FO monthly solutions for the Aral Sea region. As the closeness of the Caspian Sea may influence the monthly mass variations of the Aral Sea, it has also been involved in the investigations. According to the results, GRACE-FO models seem to continue the mass variations of the GRACE period properly, therefore their use jointly with GRACE is suggested. Based on the justified characteristics of the gravity anomaly by water volume variations in the case of the Aral Sea, GRACE models for the period March–June 2017 are suggested to be neglected. Though the correlation between water volume and monthly gravity field variations is convincing in the case of the Aral Sea, no such a correlation for the Caspian Sea could have been detected, which suggests to be the consequence of other mass varying processes, may be related to the seismicity of the Caspian Sea area.

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Mitigation of ionospheric signatures in Swarm GPS gravity field estimation using weighting strategies

10.5194/angeo-2018-91 ◽

2018 ◽

Author(s):

Lucas Schreiter ◽

Daniel Arnold ◽

Veerle Sterken ◽

Adrian Jäggi

Keyword(s):

Gravity Field ◽

Systematic Errors ◽

Low Earth Orbit ◽

Mitigation Strategies ◽

Dual Frequency ◽

Satellite Mission ◽

Gravity Fields ◽

Data Gaps ◽

Field Estimation ◽

Grace Mission

Abstract. Even though ESA's three-satellite mission Swarm is primarily a magnetic field mission, it became more and more important as gravity field mission. Located in a low earth orbit with altitudes of 460 km for Swarm A and Swarm C and 530 km for Swarm B, after the commissioning phase, and equipped with geodetic-type dual frequency GPS receivers, it is suitable for gravity field computation. Of course the Swarm GPS-only gravity fields are not as good as the gravity fields derived from the ultra precise GRACE K-Band measurements, but due to the end of the GRACE mission in October 2017, data gaps in the previous months, and the gap between GRACE and the recently launched GRACE Follow-On mission, Swarm gravity fields became important to maintain a continuous time series and bridge the gap. By validating the Swarm gravity fields to the GRACE gravity fields, systematic errors have been observed, especially around the geomagnetic equator. These errors are already visible in the kinematic positioning from where they propagate into the gravity field solutions. We investigate these systematic errors by analyzing the geometry-free linear combination of the GPS carrier phase observations. Based on this we present different weighting schemes and investigate their impact on the gravity field solutions in order to assess the success of different mitigation strategies.

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