IAC-12-A3.5.3 − Page of 7 1 RETURN TO VENUS OF THE JAPANESE VENUS CLIMATE ORBITER AKATSUKI Masato Nakamura Institute of Space and Astronautical Science, Japan, nakamura.masato@jaxa.jp Yasuhiro Kawakatsu * , Chikako Hirose * , Takeshi Imamura * , Nobuaki Ishii * , Takumi Abe * , Atsushi Yamazaki * , Manabu Yamada † , Kazunori Ogohara * , Kazunori Uemizu * , Tetsuya Fukuhara ‡ , Shoko Ohtsuki § , Takehiko Satoh * , Makoto Suzuki * , Munetaka Ueno * , Junichi Nakatsuka * , Naomoto Iwagami ** , Makoto Taguchi †† , Shigeto Watanabe ‡ , Yukihiro Takahashi ‡ , George L. Hashimoto ‡‡ , and Hiroki Yamamoto * Japanese Venus Climate Orbiter/AKATSUKI was proposed in 2001 with strong support by international Venus science community and approved as an ISAS (The Institute of Space and Astronautical Science) mission soon after the proposal. The mission life we expected was more than two Earth years in Venus orbit. AKATSUKI was successfully launched at 06:58:22JST on May 21, 2010, by H-IIA F17. After the separation from H-IIA, the telemetry from AKATSUKI was normally detected by DSN Goldstone station (10:00JST) and the solar cell paddles’ deployment was confirmed. After a successful cruise, the malfunction happened on the propulsion system during the Venus orbit insertion (VOI) on Dec 7, 2010. The engine shut down before the planned re- duction in speed to achieve. The spacecraft did not enter the Venus orbit, but entered an orbit around the Sun with a period of 203 days. Most of the fuel still had remained, but the orbital maneuvering engine was found to be broken and unusable. However, we have found an alternate way of achieving orbit by using only the reaction control system (RSC). We had adopted the alternate way for orbital maneuver and three minor maneuvers in Nov 2011 were successfully done so that AKATSUKI would meet Venus in 2015. We are considering several scenarios for VOI using only RCS. I. INTRODUCTION Venus is our nearest neighbor and has a size very similar to the Earth’s; however, previous spacecraft missions discovered an extremely dense (~92 bar) and dry CO2 atmosphere with H2SO4-H2O clouds floating at high altitudes, and exotic volcanic features covering the whole planet. The abundant gaseous CO2 brings about a high atmospheric tem- perature (~740 K) near the surface via greenhouse effect. The atmospheric circulation is also much different from the Earth’s. The mechanisms that sustain such conditions are unclear and considered to be the keys to understanding the origin of the ter- restrial environment. Japanese Venus Climate Orbiter/AKATSUKI was proposed in 2001 to address the mysterious Venusian atmosphere with strong support by inter- national Venus science community and approved as an ISAS mission soon after the proposal [1, 2]. PLANET-C was the given project code name in ISAS. AKATSUKI and ESA’s Venus Express have been expected to complement each other in Venus climate study. Various coordinated observations using the two spacecraft have been planned. Also participating scientists from the U.S. have been se- lected. The mission life we expected was more than two Earth years in Venus orbit. AKATSUKI was successfully launched at 06:58:22JST on May 21, 2010, by H-IIA F17. After the separation from H-IIA, the telemetry from AKATSUKI was normally detected by DSN Gold- stone station and the solar cell paddles’ deployment was confirmed. AKATSUKI was put into the three-axis stabilized mode in the initial operation from Uchinoura station and the critical operation was finished at 20:00JST on the same day. * Institute of Space and Astronautical Science, Japan, surname.givenname@jaxa.jp † Planetary Exploration Research Center, Chiba Institute of Technology, Japan, manabu@perc.it-chiba.ac.jp ‡ Hokkaido University, Japan, tetsuyaf@ep.sci.hokudai.ac.jp, shw@ep.sci.hokudai.ac.jp, yukihiro@mail.sci.hokudai.ac.jp, § Senshu University, Japan, oh@isc.senshu-u.ac.jp ** University of Tokyo, Japan, iwagami@eps.s.u-tokyo.ac.jp †† Rikkyo University, Japan, taguchi@rikkyo.ac.jp ‡‡ Okayama University, Japan, george@gfd-dennou.org