ESA GNC Conference Papers Repository

The Geostationary Operational Environmental Satellite-R (GOES-R) spacecraft was launched on November 19, 2016, and the spacecraft is now on station in geosynchronous orbit and renamed GOES-16. The GOES-R series of spacecraft is the next generation of advanced geosynchronous weather satellites for the United States operated by the National Oceanic and Atmospheric Administration (NOAA). When fully deployed, the GOES-R spacecraft features a number of flexible appendages with modal frequencies below 3.0 Hz which, if excited, can be sources of undesirable jitter perturbing spacecraft pointing. In order to meet the GOES-R Guidance Navigation and Control (GN&C) subsystem pointing stability requirement of 221 µrad (or 46 arcseconds) peak-to-peak per axis over 60 seconds, the GOES-R flight software implements an Active Vibration Damping (AVD) rate control law which acts in parallel with the nominal mission Single Input Single Output (SISO) nadir point attitude control law. The AVD controller commands spacecraft reaction wheel actuators based upon Inertial Measurement Unit (IMU) inputs to provide additional damping for spacecraft structural modes below 3.0 Hz which vary with solar wing angle. A GOES-R spacecraft and attitude control system identified model is constructed from pseudo-random reaction wheel torque commands and IMU angular rate response measurements occurring over a single orbit during spacecraft post-deployment activities. Ground processing algorithms perform a least-squares Fourier fit of these data as a function of solar wing angle to identify the exact character of the combined spacecraft on-orbit structural dynamics and nadir point attitude control law. The Fourier model coefficients are uplinked and stored by the spacecraft flight computer and used over the entire mission duration; at every two-degrees of solar wing rotation, the AVD controller filter coefficients are updated on-board from the Fourier model. Consequently, the AVD controller formulation is based not upon pre-launch simulation model estimates but upon actual on-orbit nadir point attitude control and time-varying spacecraft dynamics. GOES-R high-fidelity simulation results are shown which demonstrate that the AVD controller provides as much as a ten-fold increase in structural mode damping with robust performance control while maintaining controller stability margins and ensuring that the nadir point attitude control bandwidth does not fall below 0.02 Hz. Finally, the on-orbit GOES-16 spacecraft appendage modal frequencies and damping ratios are quantified based upon the AVD system identification, and the increase in modal damping provided by the AVD controller for each structural mode is presented. The GOES-16 spacecraft AVD controller frequency domain stability margins and nadir point attitude control bandwidth are presented along with on-orbit time domain disturbance response performance.