In order to characterize the thermal performance of the spacecraft at attitudes beyond initial constraints and to expand the operational envelope, on-orbit testing was performed. Plans and tradeoffs in preparing for the testing are discussed. Results are presented and compared with analytical predictions.Although the payload and bus sections were only separately thermal vacuum tested prior to flight, results from the on-orbit testing indicate the integrated thermal design is robust. One thermal anomaly was discovered which is attributed to specular reflections from a radiator. The influence of the on-orbit testing results on spacecraft continuing operations is also discussed.