Development of embedded star catalog for autonomous star trackers

Abstract

In May 2012, the federal government approved by decree No. 224 / GC3 the Strategic Program for Space Systems (PESE), prepared by the Ministry of Defense, through the Air Force Command. Its content deals with the wishes of the three forces in the coming decades in terms of satellites and functionality applied to the defense of the national territory. To cover the different demands, the country will need to develop different critical technologies. One of the technologies not yet dominated by Brazil is the Attitude and Orbit Control System (AOCS). The attitude control is performed in closed loop, by a set of sensors and actuators, which are driven by different control loops configurations depending on the pointing accuracy required and the operation phase of the mission. The autonomous star tracker is currently the most accurate orientation sensor in the market, being the subject of study and development of this proposal and the only sensor that makes it possible to achieve the requirements of the PESE, for several of its satellites. It is then a necessary technology. An autonomous star sensor is an optoelectronic device that autonomously determines the orientation of a satellite. To this end, it performs stellar observations and records them in the form of images, comparing them to an embedded star catalog, thus allowing determination of the angular position of the spacecraft in its three axes of rotation. Therefore, an essential part of determining autonomously attitude of a star tracker is the embedded star catalog. With this in mind, the proponent of this project has begun in March 2014 its development as a scientific research work. The main results obtained so far are: reading, validation and generation of human-machine interface of public data from the Hipparcos star catalog (European Space Agency); projection of a star on the photoelectric detector of the sensor, taking into account the response of the optical system, the instrument geometry and other instrumental characteristics; generalization to an observed field; detection of the stars and star clusters; and determination of their respective barycenters. This proposal aims the completion of the development of the embedded star catalog and subsequent evaluation of the measurement accuracy of the star tracker according to the catalog itself and instrumental parameters, by building a sensor precision map of all the celestial sphere. To do so, the development of some algorithms must be completed as well as the integration of others in development by other team members. This research project thus describes briefly in his body how these goals will be achieved and the means to do so.