On-orbit modal identification of the Hubble Space Telescope

In order to understand the dynamic environment incurred by the on-orbit replacement Hubble Space Telescope solar arrays, two on-orbit forcing function tests were conducted shortly after the spacecraft servicing mission. These tests were necessitated by the fact that even with the new solar arrays, spacecraft jitter exceeded the spacecraft's extremely tight pointing requirements. The first test was conducted to determine the modal frequencies of interest. The second test was conducted to determine the gain and damping for the spacecraft significant modes. The data from the second test was reduced and a set of modal gains and damping was developed; this spacecraft model has been verified through observation of flight data. Using this new plant data, compensation is presented in this article which attenuates the spacecraft jitter associated with the spacecraft modes.