ESA GNC Conference Papers Repository

SPACESTAR is a novel star tracker architecture, originally developed for a high volume constellation program which, through an integrated configuration to Attitude Control System computers, enables significant size, weight, power and cost benefits. The results of these efficiencies provide the ability to utilize high performance star tracking systems on small satellites that were previously unable to accommodate the size, weight, and power of legacy architectures. State-of–the-art star sensors are constituted by an optical system, a detector and a computer that executes image processing and attitude measurement algorithms. The computer may be separated from the housing which hosts the optics and the detector, but is always fully devoted to executing the star sensor SW. The availability of computers with increased computational capability in the state-of-the-art spacecraft’s defines an innovative architecture of star sensors, in which the main spacecraft Platform Computer (PFC) hosts, further to the attitude control SW, also the stars’ tracking SW (to compute the attitude quaternion in the J2000 Inertial Reference Frame). The SPACESTAR star sensor HW is thus limited to Optical Heads, each hosting the optics, the detector and the small portion of digital electronics needed to operate the detector and perform communication with the PFC. The SPACESTAR Star Tracker SW is optimised to use at best the improved computational capability of onboard computers and is realised to match the tight CPU time allocation (sharing resources with all the other satellite Attitude Control System activities), without penalising robustness and reliability of the system, and even introducing additional features for simultaneous management of up to three SPACESTAR Optical Heads per satellite. Optical Head HW on Ground Qualification and SPACESTAR SW integration in spacecraft Attitude Control Computer SW was already achieved within a high volume constellation program. The paper further describes this product capabilities and the challenges encountered during its development.