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A.3 - GRACE Follow-On
(Convener: )
GRACE-FO Mission Status
(M. Watkins, F. Flechtner)
Development status of the electrostatic accelerometer for the GRACE Follow-On mission
(B. Foulon, B. Christophe, D. Boulanger, V. Lebat, F. Liorzou)
Bridging the potential GRACE/GRACE-FO gap by high-low SST observations only
(C. Dahle, K.-H. Neumayer, G. Michalak, F. Flechtner)
Bridging the Gap via EOF Fitting
(M. Talpe, S. Nerem, F. Lemoine, R. E. Riva, D. Chinn, E. Pilinski)
Title: GRACE-FO Mission Status
Presenter: Watkins, Michael
Co-Authors: F. Flechtner
Abstract: Status update on the GRACE Follow-On Mission
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Title: Development status of the electrostatic accelerometer for the GRACE Follow-On mission
Presenter: Christophe, Bruno
Co-Authors: B. Foulon; B. Christophe; D. Boulanger; V. Lebat; F. Liorzou
Abstract: The design of the electrostatic space accelerometers developped by Onera for the GRACE Follow-On mission is very similar to the one of the SuperStar accelerometers operating in orbit on board the twin GRACE satellites since more than eleven years. Nevertheless, they take also into account the return of experience of those constituting the Electrostatic Gravity Gradiometer of the GOCE ESA mission. In particular, the thermal stability of the front end electronics functions and a more accurate survey and recording of many instrument internal temperatures should allow an improvement of the acceleration measurement data. Inherited from the pendulum ground testing of the GOCE accelerometers and of the drop tower catapult tests of the MICROSCOPE differential accelerometer, more accurate pre-launch calibrations should also help for a better mission scientific return. The presentation will also provide the present status of the GFO accelerometer just before its Preliminary Design Review.
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Title: Bridging the potential GRACE/GRACE-FO gap by high-low SST observations only
Presenter: Dahle, Christophe
Co-Authors: K.-H. Neumayer; G. Michalak; F. Flechtner
Abstract: Global time-variable gravity field models play an essential role for many geophysical applications such as assessing ice mass loss, variations in continental hydrology or fluctuations of oceanic masses. Their capability to do so is strongly related to the twin-satellite mission GRACE (launched in 2002) and especially to the low-low SST (Satellite-to-Satellite Tracking) K-band link between both spacecrafts enabling, in combination with GPS based high-low SST, high sensitivity and accuracy in long and mid gravity field wavelengths.
Currently, GRACE has exceeded its designated life-time of 5 years by far and limitations in data processing due to switch-off of instruments caused by battery problems are already present. This situation might even get worse and also a complete end of the mission might happen in the near future. Therefore a notable data gap till launch of the GRACE follow-on mission (GRACE-FO) in summer 2017 is likely.
In order to provide at least information about large-scale variations of the Earth's gravity field during this gap, we investigate the capability of gravity field solutions based on high-low SST only. In view of the possible scenario of having two GRACE satellites without K-band link as well as with regard to the upcoming SWARM mission to be launched in November this year consisting of three satellites equipped with GPS and accelerometers, the potential benefit of using GPS-derived baselines between satellites as additional information is also investigated. Real data from CHAMP and GRACE is used to assess the possibilities and limits of such solutions compared to standard, i.e. K-band based, GRACE solutions.
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Title: Bridging the Gap via EOF Fitting
Presenter: Talpe, Matthieu
Co-Authors: M. Talpe; S. Nerem; F. Lemoine; R. E. Riva; D. Chinn; E. Pilinski
Abstract: In this work, we seek to extend the time-dependent record of gravity beyond the time frame of the GRACE mission via Empirical Orthogonal Functions (EOF). The EOF spatial modes of the GRACE Release 5 fields are combined with the temporal modes of conventional tracking data, determined from normal equations of SLR and DORIS tracking, to generate reconstructed fields. These reconstructed fields are global fields of GRACE resolution (up to degree and order 60) covering the timespan of the conventional tracking data (1993 - present).
Preliminary results indicate that the Antarctica and Greenland ice sheet mass change curves of the reconstructed fields match with mass change values from GRACE found in recent literature.
We further investigate several aspects of the EOF fitting process:
- by using individual fingerprints of Greenland and Antarctica [Riva, et al., 2010] as spatial fields. The EOF fitting is also compared to a least-squares fit of the fingerprints with the conventional tracking data series.
- by fitting GRACE fields that have been modified--whereby the fingerprint signals described above are first removed from the GRACE fields when decomposed to spatial modes by EOFs and then added individually when fitting with conventional tracking data.
- by comparing the influence of a different SLR solution to the EOF fitting
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