On-Orbit Validation of Gyroscope Calibration and Optical Link Performance on QUBE

Kurzfassung

Free-space optical communication enables high-data-rate, power efficient links for small satellite missions and is a key enabler for space-based quantum key distribution (QKD). However, the narrow beam divergence of optical links imposes stringent requirements on pointing accuracy, particularly during link acquisition between space-based terminals. Unlike space-to-ground links, inter-satellite optical terminals must rely solely on onboard resources, making attitude uncertainties and misalignments between spacecraft attitude determination and control systems (ADCS) and laser communication terminals (LCTs) a challenge. The QUBE mission, which demonstrates experiments towards QKD, is used to verify LCT internal gyroscope calibration and to analyse the performance of the optical space-to-ground link. This work therefore presents the validation of an on-orbit calibration method for CubeSat-class optical terminals by aligning an LCT gyroscope with the spacecraft ADCS reference frame. Additionally, the alignment between LCT and ADCS reference frames is estimated based on high-rate tracking data from the fast-steering mirror that provides the mean offsets with respect to the satellite’s body-pointing during closed-loop tracking. On-orbit pointing, acquisition and tracking results from optical downlinks demonstrate rapid acquisition times of 2 seconds, and tracking of up to 97.5% of the total operation time, equivalent to 7 minutes and 25 seconds.