When
Thursday, April 10, 2025 at 4:00 p.m.
Fabio Curti
Associate Professor
Department of Systems and Industrial Engineering
University of Arizona
"Gyroless Angular Rate Determination based on Star Sensor Images"
AME Lecture Hall, Room S212
Zoom link
Abstract: A fully gyroless solution would reduce AOCS costs and complexity. G yros tend to degrade or fail in orbit and may not be included in some small spacecraft designs. In such scenarios, there is always a need to estimate the angular rate, and a fully gyroless solution offers significant cost savings while simplifying AOCS architecture. The focus is on estimating angular rates from star tracker images without impacting the star tracking functions, regardless of the magnitude of the body’s angular rates or the update rate of the star tracker. This approach involves processing and comparing consecutive images for noise filtering while maintaining the continuity of the star tracking function without requiring star identification.
At low angular rates, up to 5°/s, the angular velocity estimate is based on a modified Wahba problem and uses a differentiation approach that does not rely on the spacecraft dynamics model. An Extended Kalman Filter (EKF) filters out spikes due to uncertainties in the centroids’ measurements. At higher angular rates, up to 20°/s or more, the star tracker acquires images with streaks corresponding to stars in the sensor's field of view (FOV). One important aspect is determining the length of the arc related to a generic star, from which the angular velocity can be derived. The proposed algorithm for high angular rate estimation is divided into three phases: determining the sign, determining the direction in the Sensor Reference Frame (SRF), and determining the rate based on the streak length.
This study focuses on star sensors using APS technology for the detector. The APS sensor line read-out time introduces image distortion in which the streaks are stretched or shortened, depending on whether the star moves in the image plane in the same direction or in the opposite direction of the line read-out. This effect is non-negligible, as it induces an error of about 25% in estimating the streak length. The High-Rate Mode for angular velocity estimation enables reliable and accurate rate measurements, which are essential for de-tumbling satellites and allowing star trackers to switch back to tracking mode.
Bio: Fabio Curti is an associate professor in the Department of Systems and Industrial Engineering at the University of Arizona. He is a member of the Space Automation and Robotics Technical Committee of the American Institute of Aeronautics and Astronautics (AIAA) and the Study Group Through Optimization of Aerospace Trajectories of the International Academy of Astronautics (IAA).
He has authored or co-authored approximately 150 papers in international peer-reviewed journals and conferences, as well as two patents in the AOCS field. His research topics include Space Domain Awareness, Guidance, Navigation and Control, Space Robotics, Attitude Determination and Control and Space Proximity Maneuvers.