Developing and enriching a guidance library for the Earth Observation Satellite MicroCarb

Sammanfattning: My Master Thesis takes place in the context of the MicroCarb mission. The goal of this mission is to identify the sinks and the sources of carbon dioxide on Earth in order to map them and to improve the knowledge of its cycle. To fulfill this mission, some particular guidance modes must be implemented in order to study their feasibility. My thesis consisted in defining and enriching the algorithms used to define the guidance laws, by implementing new tools and a new guidance law, and studying the induced performances in terms of data acquisition and with respect to the constraints related to the satellite. Alongside with this mission, the implementation of those elements support the development of the guidance library POLARIS, actual in its early phase, which is at first only dedicated to MicroCarb but which is intended to become multimissions. First, I describe the CNES as well as the guidance team I worked in. Then, the context of the Master Thesis is introduced. Once the context is established we will focus on the first elements I have been working on, as part of the Dazzling studies. Indeed, the spectrometer used in MicroCarb is very sensitive and has to be maintained at very low temperature. Thus the passive cooling mechanism must be protected from the Sunlight and from the light reflected by the Earth. I had to use a class of the Space mechanics library PATRIUS, called Assembly, in order to materialize the satellite and its numerous parts. Once implemented, I was able to perform some Dazzling Studies, highlighting some issues with the various strategies that were considered, and opening new perspectives. Moreover, a problem was detected on a crucial function of the guidance laws calculator. Once a new function was compiled, I had to made a cross validation using Scilab, and results were positive. This part will end with a Geometric Cape study, realized in order to quantify the influence of the satellite, and the MCV roll, over the Geometric Shifting. In the second part, we will introduce a guidance law which was not implemented initially, and on which I had to work during the last weeks of the thesis: The City mode. Although this mode is similar to an existing calibration mode, it has its own characteristics I had to take into account. The code for this acquisition mode worked well, but the results were not satisfying, considering the Dazzling problem and the kinematic constraints. Thus new strategies had to be considered, and more particularly the 2-scans mode. This mode brought a lot of satisfactions, but there is still more work to be done. This report ends with a general conclusion about my work and some perspectives which could be considered for future studies. I also present my personal contribution and some encountered difficulties I had to deal with.