Study of Pitch Attitude Estimation Using a High-Definition TV (HDTV) Camera on the Japanese Lunar Explorer SELENE (KAGUYA)

The lunar explorer SELENE was launched on September 14, 2007, and impacted the Moon on June 11, 2009. KAGUYA carried thirteen scientific mission instruments to reveal the origin and evolution of the Moon and to conduct utilization of the Moon. In addition to the scientific instruments, a High-Definition TV (HDTV) camera provided by the NHK was carried on KAGUYA to promote public outreach. When a malfunction of KAGUYA reaction wheel occurred, we found that using horizon information of the lunar surface derived from HDTV moving images as a horizon sensor to detect KAGUYA attitude was very useful. We usually use housekeeping telemetry data to derive satellite attitude along with orbital determination and propagated information. However, it takes time to derive that information since orbital determination and propagation calculation requires using the orbital model. Since deriving KAGUYA pitch angle change information from HDTV moving images is a very simple and quick method, we estimated pitch angle changes during KAGUYA mission operation using HDTV moving images. We then compared this information with attitude information derived from orbital telemetry information and validated the accuracy of HDTV derived estimation. We show the usefulness of an HDTV camera as a horizon sensor in this study.