Abstract
This paper presents the IOV and FOC Battery in orbit trend analysis and degradation modelling based on the Galileo experience in the frame of the ESPC 2016. Galileo provides a unique opportunity to study a constellation of satellites in the Medium Earth Orbit (MEO) to make a statistical analysis of power sources degradations due to its environment.From a project point of view the objective of the study is to establish a process to obtain the in-orbit battery degradations. Accurate battery degradation knowledge will allow precise battery management from operation teams (battery fade strategy and combined Earth Lunar eclipse power estimations). Another key feature of this study is to be able to assess different battery performance (Saft and ABSL) under very similar mission requirements over a long period (electrical profile, temperature, and environment).This paper reports on the first four years in orbit of IOV PFM satellite (10 eclipse seasons and still running) and on-going FOC satellite telemetry (TM) analysis (starting with two years of data from FOC GSAT201 and GSAT202).The results are in all cases better than the predictions, which is expected due to the usage of conservatives assumptions in the design to cover (for both IOV and FOC) worst case scenario for the entire constellation. It should be noted that the FOC GSAT201 and GSAT202 batteries are degrading slightly faster than the 6 others FOC batteries identified GSAT203, GSAT204, GSAT205, GSAT206, GSAT208 and GSAT209, but still below predictions due to their peculiar unexpected orbit reached after launch (higher DoD up to 42% measured due to longer eclipses). These 2 satellites will require specific degradation monitoring.
Highlights
The Galileo satellites compose a constellation in the Medium Earth Orbit (MEO) Orbit
BEAST models are feed with in-orbit telemetry of the battery current and temperatures during the discharge and charge phase, the Beast simulation voltage is adjusted to the in-orbit battery voltage applying the battery capacity degradation coefficient and the internal resistance increase
This study provides a quantitative data on the in-orbit performance of the Galileo satellite batteries which could be used for in-orbit trend analysis
Summary
The Galileo satellites compose a constellation in the MEO Orbit. It is composed of 24 reference satellites on 3 orbital planes separated by 120° right ascension of the ascending node (Plane A, B and C). Galileo is on a circular orbit of 29 600 km, at an inclination of 56°. The satellites design lifetime is 12 years. IOV batteries telemetry have been acquired and postprocessed. Using the current and temperature profiles during the longest Earth Eclipses and applying this profile into on-ground simulation tools, the battery degradation parameters could be obtained.
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