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Portail > Offres > Offre UMR5563-JEALEM-003 - Etude de faisabilité d'une solution du champ de gravité variable à haute résolution temporelle et basse résolution spatiale (H/F)

Feasibility study of a variable gravity field solution with high temporal resolution and low spatial resolution (M/F)

This offer is available in the following languages:
Français - Anglais

Date Limite Candidature : lundi 10 octobre 2022

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General information

Reference : UMR5563-JEALEM-003
Workplace : TOULOUSE
Date of publication : Monday, September 19, 2022
Type of Contract : FTC Technical / Administrative
Contract Period : 12 months
Expected date of employment : 7 November 2022
Proportion of work : Full time
Remuneration : between 2663 and 3953 € gross monthly depending on experience (CNRS grid)
Desired level of education : 5-year university degree
Experience required : Indifferent

Missions

For several decades, CNES in collaboration with GRGS, has been producing series of the Earth's gravity field with a monthly and ten-day temporal resolution, at a spatial resolution of around 300 km.
The main objective of the CDD will be to set up a rapid processing chain for GRACE-FO data to produce, with a short delay, low spatial resolution gravity field solutions (around 30 degrees of spherical harmonics) and high temporal resolution in order to be able to feed applications requiring precise orbitography (altimetry in particular) with little delay. The precise orbitography of these satellites has in fact relied until now on average models calculated from GRACE and GRACE-FO data, models which do contain variable terms (annual drifts, annual and semi-annual periodic signals) but whose updating can only be done with a delay of one or even several years. During this lapse of time the gravity field model works in extrapolation, which can prove to be problematic. The needs of these missions in orbitographic precision require a much more frequent update, mainly on the longer wavelengths.
In a second step, the incumbent will study the possibility of using these "low resolution - high frequency" solutions to improve the monthly solutions by reducing the residual "aliasing" effect coming from the errors of the atmospheric and oceanic dealiasing models. and short-scale temporal variations in terrestrial hydrological content (method of Wiese, 2011).
The incumbent will participate in international conferences and a publication. Fluency in English is mandatory.

Activities

Main tasks :
- Bibliographic research on the subject
- Getting started with existing tools for calculating gravity field models
- Determination of the optimal compromise between spatial resolution and temporal resolution for fast solutions of the gravity field
- Implementation of an operational GRACE-FO data processing chain (and SLR if necessary)
- Writing of a scientific paper detailing the results obtained

Secondary tasks:
- study of the Wiese method and evaluation of its contribution to monthly solutions in terms of dealiasing
- Presentation of results in international conferences (EGU, AGU, GRACE Science meeting...)

Skills

- reasonable knowledge in spatial geodesy
- mandatory knowledge of a programming language (preferably Fortran, otherwise C or Python), the Linux environment and scripts writing
- taste for scientific analysis
- fluency in English essential

Work Context

The place of work will be the GET laboratory "Géosciences Environnement Toulouse" (UMR5563) which is centered on the study of the internal Earth, its continental surfaces and interfaces and the environment.
This joint CNRS research unit of around 230 people (156 permanent staff and more than 70 PhD students and CDD researchers) is located within the Midi-Pyrénées Observatory, in the Rangueil scientific complex in Toulouse.
In this laboratory, a team of around ten CNES agents works more specifically on terrestrial and planetary space geodesy.
The work will be done in collaboration with the LEGOS laboratory team, also located at the OMP.
Possibility of renewal of one year of the contract.

Constraints and risks

not relevant

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