On-orbit Properties and Initial Results of SELENE / KAGUYA Small Sub-satellites OKINA & OUNA for Lunar Gravity Mapping
- Paper number
IAC-08.A3.2.A4
- Author
Prof. Takahiro Iwata, Japan Aerospace Exploration Agency (JAXA), Japan
- Coauthor
Mr. Hiroyuki Minamino, Japan Aerospace Exploration Agency (JAXA), Japan
- Coauthor
Dr. Noriyuki Namiki, Kyushu University, Japan
- Coauthor
Prof. Hideo Hanada, National Astronomical Observatory of Japan, Japan
- Coauthor
Dr. Hirotomo Noda, National Astronomical Observatory of Japan, Japan
- Coauthor
Dr. Koji Matsumoto, National Astronomical Observatory of Japan, Japan
- Coauthor
Prof. Nobuyuki Kawano, National Astronomical Observatory of Japan, Japan
- Coauthor
Mr. Seiitsu Tsuruta, National Astronomical Observatory of Japan, Japan
- Coauthor
Dr. Qinghui Liu, National Astronomical Observatory of Japan, Japan
- Coauthor
Dr. Fuyuhiko Kikuchi, National Astronomical Observatory of Japan, Japan
- Coauthor
Dr. Ishihara Yoshiaki, National Astronomical Observatory of Japan, Japan
- Coauthor
Prof. Tadashi Takano, Japan Aerospace Exploration Agency (JAXA), Japan
- Coauthor
Dr. Sander Goossens, National Astronomical Observatory of Japan, Japan
- Year
2008
- Abstract
SELENE Main Orbiter (KAGUYA) has successfully separated two small sub-satellites; (1) the Relay Satellite OKINA (Rstar), and (2) the VLBI Radio Satellite OUNA (Vstar). OKINA and OUNA were injected into the elliptical lunar orbit of 2,395-120 km in altitude on Oct. 9, 2007, and 792-129 km on Oct. 12, 2007, respectively. Both OKINA and OUNA are spin-stabilized small satellites which have octagonal prism main bodies measured as 1 m x 1 m x 0.65 m. The total mass of each satellite was determined to be 45 kg in the ground tests. These sub-satellites have started to perform 4-way Doppler measurements using Relay Satellite Transponder (RSAT), multi-frequency phase-delay differential VLBI observation using VLBI Radio Sources (VRAD) for global and precise mapping of lunar the gravity field, and Radio Science observations (RS) for detecting lunar ionosphere. Initial check out were executed and properties of satellite bus equipments, onboard mission instruments, and observation systems including ground stations were evaluated between October and November in 2007. These results have shown that both the sub-satellites perform enough quality to produce efficient scientific data for RSAT/VRAD/RS missions. The maximum electric power of the solar array is estimated as more than 120 W, which is higher than the demand initial value. In this paper, we also report the initial results of the global and precise gravity distribution. Our first light of SELENE from the lunar far side were obtained during the initial checkout, and suggested that we have detected gravity anomalies which could not be observed previously because of the lack of four-way Doppler methods. Our free air gravity distributions argue the possible dichotomy on the interior structure of the Moon.
- Abstract document
- Manuscript document
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