An in-orbit Diagnostic System for Electric Propulsion Thrusters through Interferometry

Abstract

[EN] This report describes the ORBITA project in which I have worked for AVS (Added Value Solutions) UK. The project was supported by the UK Space Agency and the European Space Agency (ESA), where the second also provided funding and offered their facilities for testing. At its core, the project had the advancement of the technology of electric thruster diagnostics as its objective. It was found in market analysis that no device exists that performs diagnostics on electric thrusters in orbit, and therefore, it was decided to pursue the development of such. Receiving thruster performance measurements during mission can allow fine-tuning of the thruster parameters, which would increase its lifetime or improve its efficiency. After the first stages of the project, consisting of a market analysis and a tradeoff of different diagnostic techniques for electric propulsion devices, my involvement begun in the development stage. A Fabry-P´erot interferometer was chosen as the diagnostic technology to be developed. By measuring the frequency of the Doppler shifted light emitted by the xenon plasma plume of an electric propulsion device, its exhaust velocity could be calculated. I fulfilled a secondary role in the mechanical design, where I aided and gave advice to the colleague responsible for this part. With the optical system, my involvement also included the procurement of components from the manufacturers, ensuring their compatibility with our device. However, my main tasks were related to software development. I wrote a Python program that controls rotational stages key to the interferometer, while also taking measurements and saving them, automatizing the most repeated steps in the operation of the device. Based on simulations of data expected to measure in testing, I also wrote the program responsible of processing the data, to extract the exhaust velocity from it, and integrated both programs. Finally, I also made the proof-of-concept version of a secondary system that involves an Arduino board and an stepper motor. In the design of a breadboard version of a diagnostic device, my personal objective was to ensure the correct functioning of the parts of the system entrusted to me, as well as helping the rest of the team at my fullest capacity for the whole system to give satisfactory results when testing. In this text, the theoretical framework necessary to understand the project and why the parameters that it measures can be of interest will be introduced. Then, after a more detailed explanation of the project, the developed system’s main parts will be explained, with added emphasis on the programs developed by myself. Finally, the performed test will be described, including the results obtained and the conclusion that were taken from them.