BSc or MSc thesis

Data Analysis: Validation of force models for GRACE Follow-On (BSc or MSc thesis)

Job Offer from March 10, 2020

GRACE Follow-On (Gravity Recovery and Climate Experiment) is a joint DLR/NASA space mission, comprising of two identical spacecraft in almost identical low Earth orbits. By precisely tracking the inter-spacecraft distance variations, it is possible to deduce Earth’s underlying gravity potential. Besides the static part of this gravity potential, it is also possible to compare monthly “snapshots” of the gravity field and use these to keep track of many features of the hydrological cycle, for example ground-water storage, ice-cap mass loss and the global sea-level. In addition to the microwave-ranging instrument, which has already been used for the original GRACE mission (2002-2017), GRACE-FO uses a novel Laser Ranging Interferometer (LRI) for the ranging measurements.

In the past years, the AEI has largely contributed to the development of the LRI architecture and the testing of the hardware. Since the launch and commissioning of the spacecraft in May 2018, we continuously monitor the telemetry and analyze the data quality to learn about the instrument’s behavior in space and possible aging processes.

Besides the instrument-level investigations, the GRACE-FO LRI group at the AEI is interested to learn about the instrument’s data quality after subtracting the modeled motion from the measured ranging data. This modeled motion can be derived from various force models. This will help to determine the instrument noise sources. In order to compute the forces acting on the orbiters, we use a collection of in-house developed matlab routines - called the gravity field recovery (GFR) toolbox.

This project focuses on validating and improving the GFR toolbox. The student will learn about

  • state-of-the-art force models for spacecraft in a low-Earth orbit, i.e. third body forces, atmospheric drag, static and dynamic Earth gravity field.
  • programming in a collaborative environment using git and gitlab
  • numerical methods and data analysis techniques

Once the code of the GFR toolbox is validated, we might use it for precise orbit determination and gravity field recovery.

The GFR software is written in Matlab programming language. A theory background in physics and/or geodesy, as well as experience in programming (Matlab or Python) is preferred for this project.

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