A Posteriori De-aliasing of Ocean Tide Error in Future Double-Pair Satellite Gravity Missions

2016 ◽  
pp. 103-109
Author(s):  
W. Liu ◽  
N. Sneeuw ◽  
S. Iran Pour ◽  
M. J. Tourian ◽  
T. Reubelt
Keyword(s):  
Ocean Tide ◽  
A Posteriori ◽  
Satellite Gravity ◽  
Satellite Gravity Missions

Effect of Ocean Tide on Recovery of Satellite Gravity Field

2007 ◽  
Vol 50 (1) ◽  
pp. 116-123 ◽  
Author(s):  
Jiang-Cun ZHOU ◽  
He-Ping SUN
Keyword(s):  
Gravity Field ◽  
Ocean Tide ◽  
Satellite Gravity

Unconstrained global simulations of ocean tides up to degree 3 for satellite gravimetry

2021 ◽  
Author(s):  
Roman Sulzbach ◽  
Henryk Dobslaw ◽  
Maik Thomas
Keyword(s):  
Signal To Noise Ratio ◽  
Relative Accuracy ◽  
Ocean Tide ◽  
Groundwater Depletion ◽  
Altimetry Data ◽  
Satellite Gravity ◽  
Tidal Model ◽  
Rotation Scheme ◽  
Gravimetric Data ◽  
High Level

<p>Tidal de-aliasing of satellite gravimetric data is a critical task in order to correctly extract gravimetric signatures of climate signals like glacier melting or groundwater depletion and poses a high demand on the accuracy of the employed tidal solutions (Flechtner et al., 2016). Modern tidal atlases that are constrained by altimetry data possess a high level of accuracy, especially for partial tides exhibiting large open ocean signals (e.g. M2, K1). Since the achievable precision directly depends on the available density and quality of altimetry data, the accuracy relative to the tidal amplitude drops for minor tidal excitations (worse signal-to-noise ratio) as well as in polar latitudes (sparse satellite-data). In contrast, this drop in relative accuracy can be reduced by employing an unconstrained tidal model acting independently of altimetric data.<br>We will present recent results from the purely-hydrodynamic, barotropic tidal model TiME (Weis et al., 2008) that benefit from a set of recently implemented upgrades. Among others, these include a revised scheme for dynamic feedbacks of self-attraction and loading; energy-dissipation by parametrized internal wavedrag; partial tide excitations by the tide-generating potential up to degree 3; and a pole-rotation scheme allowing for simulations dedicated to polar areas. Benefiting from the recent updates, the obtained solutions for major tides are on the same level of accuracy as comparable modern unconstrained tidal models. Furthermore, we show that the relative accuracy level only drops moderately for tidal excitations with small excitation strength (e.g. for minor tides), thus narrowing down the accuracy gap to data-constrained tidal atlases. Exemplarily for this, we introduce solutions for minor tidal excitations of degrees 2 and 3 that represent valuable constraints for the expected ocean tide dynamics. While they are currently not considered for GRACE-FO de-aliasing we demonstrate that third-degree tides can lead to relevant aliasing of satellite gravity fields and correspond closely to recently published empirical solutions (Ray, 2020).</p>

Consistent quantification of the impact of key mission design parameters on the performance of next-generation gravity missions

2020 ◽  
Vol 221 (2) ◽  
pp. 1190-1210 ◽  
Author(s):  
Anna F Purkhauser ◽  
Christian Siemes ◽  
Roland Pail
Keyword(s):  
Gravity Field ◽  
Laser Interferometry ◽  
Limiting Factors ◽  
Mission Design ◽  
Design Parameters ◽  
Ocean Tide ◽  
Single Pair ◽  
Post Processing ◽  
Satellite Gravity ◽  
The Impact

SUMMARY The GRACE and GRACE-FO missions have been observing time variations of the Earth's gravity field for more than 15 yr. For a possible successor mission, the need to continue mass change observations have to be balanced with the ambition for monitoring capabilities with an enhanced spatial and temporal resolution that will enable improved scientific results and will serve operational services and applications. Various study groups performed individual simulations to analyse different aspects of possible NGGMs from a scientific and technical point of view. As these studies are not directly comparable due to different assumptions regarding mission design and instrumentation, the goal of this paper is to systematically analyse and quantify the key mission parameters (number of satellite pairs, orbit altitude, sensors) and the impact of various error sources (AO, OT models, post-processing) in a consistent simulation environment. Our study demonstrates that a single-pair mission with laser interferometry in a low orbit with a drag compensation system would be the only possibility within the single-pair options to increase the performance compared to the GRACE/GRACE-FO. Tailored post-processing is not able to achieve the same performance as a double-pair mission without post-processing. Also, such a mission concept does not solve the problems of temporal aliasing due to observation geometry. In contrast, double-pair concepts have the potential to retrieve the full AOHIS signal and in some cases even double the performance to the comparable single-pair scenario. When combining a double-pair with laser interferometry and an improved accelerometer, the sensor noise is, apart from the ocean tide modelling errors, one of the limiting factors. Therefore, the next big step for observing the gravity field globally with a satellite mission can only be taken by launching a double pair mission. With this quantification of key architecture features of a future satellite gravity mission, the study aims to improve the available information to allow for an informed decision making and give an indication of priority for the different mission concepts.

scholarly journals GRAVITY ANOMALY ASSESSMENT USING GGMS AND AIRBORNE GRAVITY DATA TOWARDS BATHYMETRY ESTIMATION

2016 ◽  
Vol XLII-4/W1 ◽  
pp. 287-297
Author(s):  
A. Tugi ◽  
A. H. M. Din ◽  
K. M. Omar ◽  
A. S. Mardi ◽  
Z. A. M. Som ◽  
...  
Keyword(s):  
Gravity Anomaly ◽  
Gravity Field ◽  
Ocean Circulation ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Airborne Gravity ◽  
Satellite Gravity ◽  
Earth’S Gravity Field ◽  
Explorer Mission ◽  
Satellite Gravity Missions

The Earth’s potential information is important for exploration of the Earth’s gravity field. The techniques of measuring the Earth’s gravity using the terrestrial and ship borne technique are time consuming and have limitation on the vast area. With the space-based measuring technique, these limitations can be overcome. The satellite gravity missions such as Challenging Mini-satellite Payload (CHAMP), Gravity Recovery and Climate Experiment (GRACE), and Gravity-Field and Steady-State Ocean Circulation Explorer Mission (GOCE) has introduced a better way in providing the information on the Earth’s gravity field. From these satellite gravity missions, the Global Geopotential Models (GGMs) has been produced from the spherical harmonics coefficient data type. The information of the gravity anomaly can be used to predict the bathymetry because the gravity anomaly and bathymetry have relationships between each other. There are many GGMs that have been published and each of the models gives a different value of the Earth’s gravity field information. Therefore, this study is conducted to assess the most reliable GGM for the Malaysian Seas. This study covered the area of the marine area on the South China Sea at Sabah extent. Seven GGMs have been selected from the three satellite gravity missions. The gravity anomalies derived from the GGMs are compared with the airborne gravity anomaly, in order to figure out the correlation (R<sup>2</sup>) and the root mean square error (RMSE) of the data. From these assessments, the most suitable GGMs for the study area is GOCE model, GO_CONS_GCF_2_TIMR4 with the R<sup>2</sup> and RMSE value of 0.7899 and 9.886 mGal, respectively. This selected model will be used in the estimating the bathymetry for Malaysian Seas in future.

On the correction for polar motion in gravimetry and in 3-D positioning

2021 ◽  
Author(s):  
Jaakko Mäkinen
Keyword(s):  
Polar Motion ◽  
Low Frequency ◽  
Absolute Gravity ◽  
A Posteriori ◽  
Satellite Gravity ◽  
Polar Wander ◽  
Terrestrial Gravity ◽  
Gravity Measurements ◽  
Fixed Reference ◽  
Fixed Quantity

&lt;p&gt;In the correction for polar motion, terrestrial gravimetry and 3-D positioning follow different conventions. The 3-D positions were first corrected to refer to the &quot;mean pole&quot; (IERS Conventions up to 2010) and now to the &quot;secular pole&quot; (IERS Conventions update since 2018). In any case, the pole reference evolves in time and describes the track of secular or low-frequency polar wander. However, since 1988 terrestrial gravimetry follows the IAGBN (International Gravity Basestation Network) Processing Standards where the gravity values are corrected to refer to the IERS Reference Pole, a fixed quantity. This may lead to discrepancies when for instance gravity change rates from absolute gravity measurements are interpreted together with vertical velocities from GNSS. I discuss the size and geographical distribution of the possible discrepancies and how to account for them in geodynamical problems. The fixed reference of the IAGBN Processing Standards has served the gravity community well, by providing a stable system for terrestrial gravity for the last 30 years during which time the pole reference in the IERS Conventions has been revised several times. In fact, the recently proposed conventions for the International Gravity Reference System (IGRS) and the International Gravity Reference Frame (IGRF) maintain the IAGBN principle. However, it appears that with the adoption of the &amp;#8220;secular pole&amp;#8221; the reference in 3-D positioning may have become predictable for the foreseeable future. Therefore, it could be suggested that now is the time to harmonize terrestrial gravity with 3-D, by adopting the time-dependent secular pole as a reference for it as well, especially as this is already happening with satellite gravity. I argue that at present the practical drawbacks from such a change of reference would outweigh any theoretical advantages, and the harmonization, where necessary, can be simply performed a-posteriori to published gravity trends/values.&lt;/p&gt;

scholarly journals Geophysical Challenges for Future Satellite Gravity Missions: Assessing the Impact of MOCASS Mission

2021 ◽  
Author(s):  
T. Pivetta ◽  
C. Braitenberg ◽  
D. F. Barbolla
Keyword(s):  
Spatial Resolution ◽  
Large Scale ◽  
Cold Atom ◽  
Mountain Range ◽  
Cumulative Number ◽  
Mass Detection ◽  
Satellite Mission ◽  
Satellite Gravity ◽  
The Impact ◽  
Satellite Gravity Missions

AbstractThe GRACE/GRACE-FO satellites have observed large scale mass changes, contributing to the mass budget calculation of the hydro-and cryosphere. The scale of the observable mass changes must be in the order of 300 km or bigger to be resolved. Smaller scale glaciers and hydrologic basins significantly contribute to the closure of the water mass balance, but are not detected with the present spatial resolution of the satellite. The challenge of future satellite gravity missions is to fill this gap, providing higher temporal and spatial resolution. We assess the impact of a geodetic satellite mission carrying on board a cold atom interferometric gradiometer (MOCASS: Mass Observation with Cold Atom Sensors in Space) on the resolution of simulated geophysical phenomena, considering mass changes in the hydrosphere and cryosphere. Moreover, we consider mass redistributions due to seamounts and tectonic movements, belonging to the solid earth processes. The MOCASS type satellite is able to recover 50% smaller deglaciation rates over a mountain range as the High Mountains of Asia compared to GRACE, and to detect the mass of 60% of the cumulative number of glaciers, an improvement respect to GRACE which detects less than 20% in the same area. For seamounts a significantly smaller mass eruption could be detected with respect to GRACE, reaching a level of mass detection of a submarine basalt eruption of 1.6 109 m3. This mass corresponds to the eruption of Mount Saint Helens. The simulations demonstrate that a MOCASS type mission would significantly improve the resolution of mass changes respect to existing geodetic satellite missions.

scholarly journals Unification of European height system realizations

2012 ◽  
Vol 2 (4) ◽  
pp. 343-354 ◽  
Author(s):  
A. Rülke ◽  
G. Liebsch ◽  
M. Sacher ◽  
U. Schäfer ◽  
U. Schirmer ◽  
...  
Keyword(s):  
Gravity Field ◽  
Ocean Circulation ◽  
Reference Frames ◽  
Satellite Gravity ◽  
Global Gravity ◽  
Height System ◽  
Regional Gravity ◽  
Gravity Recovery ◽  
Satellite Gravity Missions

AbstractA suitable representation of the regional gravity field is used to estimate relative offsets between national height system realizations in Europe. The method used is based on a gravimetric approach and benefits from the significant improvements in the determination of the global gravity field by the recent satellite gravity missions the Gravity Recovery and Climate Experiment (GRACE) and the Gravity field and steady-state Ocean Circulation Explorerr (GOCE). The potential of these missions for the unification of height reference frames is analyzed in terms of accuracy and spatial resolution. The results of the gravimetric approach are compared to the independent results of the geodetic leveling approach. Advantages and drawbacks of both methods are discussed.

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