Sebastien Allgeyer

I am a scientific software developer, applying numerical methods to real world issues

The Gravity Recovery And Climate Experiment (GRACE) space gravity mission operated from 2002 to 2017. Data from the mission have had a major impact in the fields of hydrology, cryospheric science, oceanography, and glacial isostasy. The unique feature of the GRACE mission is its ability to make precise measurements of the change in the distance between the two mission satellites flying in Low Earth Orbit (LEO), enabling accurate estimates of the time evolution of the earth’s gravity field. A follow-on mission, GRACE FO, launched in 2018 with enhanced technology, provides the opportunity to continue the tracking of global mass redistribution, while reanalysis of existing data continues to provide new insights into water and ice redistribution on the earth

The goals of this project are to conduct a comprehensive analysis of the Level-1 GRACE and GRACE FO data, leading to innovative estimates of mass transport on Earth. Using in-house software to model forces on the satellites and integrate the satellite orbits, accurate gravity fields are being estimated at each stage of the mission and the resulting time variations of the gravity field used to infer mass movements on and near the surface of the earth. A particular focus in processing the Level-1 mission data is to fully understand how the mission works and the complex interactions between model errors, instrument performance and numerical instabilities when inverting for the changes in the gravity field. The aim is to understand how assumptions and decisions made in the processing of the data affect – indeed cause artefacts in – the estimated mass transport values and to test approaches to mitigate any such effects. This research will lead to improvements in the accuracy and resolution of the gravity field estimates, both temporally and spatially, and provide the capability of tracking changes in continental water storage.

Link to the ANU datacommons website (software + solutions)

References

Allgeyer, S., P. Tregoning, H. McQueen, S. C. McClusky, E‐K. Potter, J. Pfeffer, R. McGirr, A. P. Purcell, T. A. Herring, and J‐P. Montillet. “ANU GRACE Data Analysis: Orbit modeling, regularization and inter‐satellite range acceleration observations.” Journal of Geophysical Research: Solid Earth (2022): https://doi.org/10.1029/2021JB022412.

McGirr, Rebecca, Paul Tregoning, Sebastien Allgeyer, Herb McQueen, and Anthony Purcell. “Mitigation of thermal noise in GRACE accelerometer observations.” Advances in Space Research 69, no. 1 (2022): 386-401.

Interplay of Altitude, Ground Track Coverage, Noise, and Regularization in the Spatial Resolution of GRACE Gravity Field Models

Tregoning, P., R. McGirr, J. Pfeffer, A. Purcell, H. McQueen, S. Allgeyer, and S. C. McClusky. “ANU GRACE data analysis: characteristics and benefits of using irregularly shaped mascons.” Journal of Geophysical Research: Solid Earth 127, no. 2 (2022): e2021JB022412.