Eventos Anais de eventos
COBEM 2019
25th International Congress of Mechanical Engineering
STELLAR VARIABILITY MODELING FOR AUTONOMOUS STAR TRACKER SIMULATOR
Submission Author:
Luis Inagaki , SP
Co-Authors:
Luis Inagaki, Fábio de Oliveira Fialho
Presenter: Luis Inagaki
doi://10.26678/ABCM.COBEM2019.COB2019-0759
Abstract
Star trackers are key sensors in high accuracy Attitude Control Systems (ACS) for satellites. They are 3-axis orientation sensors composed by a telescope and an electronic camera. In order to develop a star tracker, simulators of various subsystems are required. Among them, the image formation simulator stands out. It simulates the complete process of creating a digital image. Star trackers rely on stars positions to derive the satellite orientation, but stars are not steady objects. Many of them evolve provoking considerable variation in their light emission. Such a stellar variability provokes inaccuracies in the satellite Line-of-Sight (LoS) calculation, once brightness variation influences the calculation of star centroid, the vary basic information used to derive the LoS. This paper aims to characterize the stellar variability, modeling and including them in an image formation simulator in order to design a robust star tracker flight software, mitigating losses of measurement accuracy of the satellite orientation. The methodology consists of determining the most common astrophysical phenomena in observable stars reachable by star trackers. To know what type of stellar variability is relevant, we use a star catalogue. Then, we create simplified models for them. Approximately, 87% over 3,338 stars with apparent magnitude Mv<=7 have relevant brightness variation in their light curves. Therefore, they impact in the performance of LoS calculation. The developed algorithms and tool allow to simulate several stellar phenomena in the same light curve. The modeling method is adequate to avoid unnecessary complexity regarding star tracker flight software development.
Keywords
Satellite, Attitude Control System, Autonomous Star Tracker, Stellar Variability, Image Formation Simulator
