ESA’s next-generation gravity mission concepts

Haagmans, Roger; Siemes, Christian; Massotti, Luca; Carraz, Olivier; Silvestrin, Pierluigi

doi:10.1007/s12210-020-00875-0

Cited by 47 publications

(22 citation statements)

References 18 publications

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“…GRACE-FO launched in August 2018 already facilitates a satellite gravity times series spanning 19 years (yet with interruptions). It will be equally important to continue this time series beyond GRACE-FO as currently jointly considered by ESA and NASA for the next generation gravity mission (Haagmans et al, 2020 (Roemmich et al, 2019) promises new observational constraints on deep ocean steric contributions.…”

Section: Discussionmentioning

confidence: 99%

Global sea-level budget and ocean-mass budget, with focus on advanced data products and uncertainty characterisation

Horwath¹,

Gutknecht²,

Cazenave³

et al. 2021

Preprint

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Abstract. Studies of the global sea-level budget (SLB) and the global ocean-mass budget (OMB) are essential to assess the reliability of our knowledge of sea-level change and its contributions. Here we present datasets for times series of the SLB and OMB elements developed in the framework of ESA's Climate Change Initiative. We use these datasets to assess the SLB and the OMB simultaneously, utilising a consistent framework of uncertainty characterisation. The time series, given at monthly sampling, include global mean sea-level (GMSL) anomalies from satellite altimetry; the global mean steric component from Argo drifter data with incorporation of sea surface temperature data; the ocean mass component from Gravity Recovery and Climate Experiment (GRACE) satellite gravimetry; the contribution from global glacier mass changes assessed by a global glacier model; the contribution from Greenland Ice Sheet and Antarctic Ice Sheet mass changes, assessed from satellite radar altimetry and from GRACE; and the contribution from land water storage anomalies assessed by the WaterGAP global hydrological model. Over the period Jan 1993–Dec 2016 (P1, covered by the satellite altimetry records), the mean rate (linear trend) of GMSL is 3.05 ± 0.24 mm yr−1. The steric component is 1.15 ± 0.12 mm yr−1 (38 % of the GMSL trend) and the mass component is 1.75 ± 0.12 mm yr−1 (57 %). The mass component includes 0.64 ± 0.03 mm yr−1 (21 % of the GMSL trend) from glaciers outside Greenland and Antarctica, 0.60 ± 0.04 mm yr−1 (20 %) from Greenland, 0.19 ± 0.04 mm yr−1 (6 %) from Antarctica, and 0.32 ± 0.10 mm yr−1 (10 %) from changes of land water storage. In the period Jan 2003–Aug 2016 (P2, covered by GRACE and the Argo drifter system), GMSL rise is higher than in P1 at 3.64 ± 0.26 mm yr−1. This is due to an increase of the mass contributions (now about 2.22 ± 0.15 mm yr−1, 61 % of the GMSL trend), with the largest increase contributed from Greenland. The SLB of linear trends is closed for P1 and P2, that is, the GMSL trend agrees with the sum of the steric and mass components within their combined uncertainties. The OMB budget, which can be evaluated only for P2, is also closed, that is, the GRACE-based ocean-mass trend agrees with the sum of assessed mass contributions within uncertainties. Combined uncertainties (1-sigma) of the elements involved in the budgets are between 0.26 and 0.40 mm yr−1, about 10 % of GMSL rise. Interannual variations that overlie the long-term trends are coherently represented by the elements of the SLB and the OMB. Even at the level of monthly anomalies the budgets are closed within uncertainties, while also indicating possible origins of remaining misclosures.

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Section: Discussionmentioning

confidence: 99%

Global sea-level budget and ocean-mass budget, with focus on advanced data products and uncertainty characterisation

Horwath¹,

Gutknecht²,

Cazenave³

et al. 2021

Preprint

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“…A large number of studies have been carried out in Europe aimed at meeting a specific set of requirements that have been tentatively adopted. A recent paper reports on some of the results from the studies: “ESA's NGGM concepts,” (Haagmans et al., 2020). However, the main results given are for a quite different mission configuration than we have been considering.…”

Section: Discussionmentioning

confidence: 99%

Improved Measurements of Short‐Period Mass Variations With Future Earth Gravity Missions

Kang

Bender

2021

JGR Solid Earth

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Satellite measurements of the Earth's time-variable gravity field are capable of addressing a wide variety of geophysical problems, such as the mass redistributions caused by hydrology, oceanography, the cryosphere, and the solid Earth. The Gravity Recovery And Climate change Experiment (GRACE) provided regular monthly estimates of the Earth's gravity field from when it was launched in 2002 (Tapley et al., 2004) until 2017 (Tapley et al., 2019). The monthly average gravity fields have been used successfully in extensive studies of changes in continental water storage, ice sheet mass, and sea level, as well as for earthquake-related deformation monitoring. Time variations in the Earth's mass distribution over periods of hours and longer are being monitored in many different ways. The results from the GRACE mission have been very valuable, but the changes in the geopotential during the usual global averaging time of about a month make it difficult to determine changes at particular locations at shorter periods. This limitation is called temporal aliasing. The satellites do not monitor the entire global field continually during a month, but sample the gravity field only along their orbital track. The resulting infrequent sampling of the signal leads to the aliasing of short-period variations into the monthly averages (see e.g., Han, 2004). For example, the short-period temporal mass variations alias into the longer period components and systematically contaminate the monthly mean gravity field estimates (see e.g., Han et al., 2006). The usual way to reduce these aliasing errors is to independently model and remove the effects of the various types of submonthly gravity variations before constructing monthly averages. But errors in these short-period gravity variation models will cause aliasing errors in the monthly gravity field solutions. The main objective of the recently launched GRACE Follow-On (GRACE-FO) Mission is to continue the roughly monthly determinations of variations in the global gravity field that were started by the GRACE mission (Landerer et al., 2020). However, GRACE-FO also carries a laser ranging interferometer (LRI) as Abstract A new mission called the Gravity Recovery And Climate change Experiment Follow-On (GRACE-FO) is now flying to continue the measurements started by the GRACE mission and to test a laser interferometry system for making more accurate measurements of the satellite separation. In this study, we discuss the potential scientific benefit of strongly reducing the acceleration noise in a Next Generation Gravity Mission (NGGM), compared with that for GRACE and for GRACE-FO. A useful way of comparing the scientific benefits is from the view point of how well they can be used to test different procedures for estimating the changes in the geopotential based on sources of geophysical information other than satellite gravity results. In particular, changes in hydrology, the atmospheric density, and ocean conditions can make large and very nonuniform changes in the geopotential in short p...

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“…Virtual Conference 30 March-2 April 2021 <500 km spatial resolution, and at 10-day intervals with <150 km spatial resolution, over a time span of at least 7 years [3].…”

Section: Icso 2020 International Conference On Space Opticsmentioning

confidence: 99%

Proof-of-concept demonstrator for the off-axis retroreflector interferometer configuration for NGGM

Dahl

Amata

Bonino

et al. 2021

International Conference on Space Optics — ICSO 2020

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This paper presents the design and breadboarding of the proof of concept demonstrator for the so called retro-reflector interferometer scheme in off-axis configuration for the 'Next Generation Gravity Mission' (NGGM) studied at the European Space Agency (ESA). This configuration can offer benefits in terms of overall satellite configuration compared to the transponder scheme, which is currently flying on board of GRACE-FO. However, it relies on very low received laser signal levels due to the fact that the laser light is travelling about 100 km from the master satellite to the remote satellite and is reflected back to the master satellite by a retro-reflector. In comparison to the transponder scheme, where the signal is amplified on the remote satellite using a laser, which is optically phase locked to the laser signal of the master spacecraft, this reflection does not amplify the signal. Thus, even with higher emitted laser power, instead of some nanowatt, only a few picowatt are available on the according science detector. Therefore, less than a femtowatt of straylight within the detectable heterodyne frequency and angular range is allowed on the detector to fulfil the ranging noise requirement.The paper gives insights into the main opto-mechanical design topics of the Optical Bench Assembly (OBA). It includes the optical analysis results as well as mechanical design to suppress straylight below the required limit. The optomechanical design of the OBA is complemented by the opto-mechanical design of the test setup and by the electro-optical design of the phase read-out chain. Finally, preliminary results from the test campaign are presented.

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ESA’s next-generation gravity mission concepts

Cited by 47 publications

References 18 publications

Global sea-level budget and ocean-mass budget, with focus on advanced data products and uncertainty characterisation

Global sea-level budget and ocean-mass budget, with focus on advanced data products and uncertainty characterisation

Improved Measurements of Short‐Period Mass Variations With Future Earth Gravity Missions

Proof-of-concept demonstrator for the off-axis retroreflector interferometer configuration for NGGM

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