Keywords:
Hayabusa2 orbit determination using c5++ software
*Keiko Yamamoto1, Toshimichi Otsubo2, Koji Matsumoto1, Hirotomo Noda1, Noriyuki Namiki1,
Hiroki Senshu3, Takahide Mizuno4, Naoko Ogawa4, Go Ono4, Yuya Mimasu4, Kent Yoshikawa4,
Tadateru Takahashi4, Yuto Takei4, Atsushi Fujii4, Fuyuto Terui4, Takanao Saiki4, Satoru Nakazawa
4, Makoto Yoshikawa4, Yuichi Tsuda4
1. National Astronomical Observatory of Japan, 2. Hitotsubashi University, 3. Chiba Institute of Technology, 4. Japan
Aerospace Exploration Agency 
Hayabusa2 arrived at the target asteroid Ryugu in June 2018 and is currently conducting remote sensing
observations with various onboard instruments. So far, we have improved orbit determination software
c5++, originally developed for the analysis of satellite laser ranging (SLR) data of the Earth, so that it can
be used for the analysis of laser ranging data between Hayabusa2 and Ryugu obtained by Hayabusa2
LIDAR. Then we used it for the estimation of Hayabusa2 trajectory and the GM value of Ryugu. However,
in the case of Hayabusa2, it is difficult to determine all of the 6 components of the initial state vector
precisely if only LIDAR range data was used, and the simultaneously estimated GM value also had large
uncertainty. To overcome this problem, in addition to LIDAR ranging data, we used
Automated-Image-Tracking (AIT) data obtained by wide-angle optical navigation camera (ONC-W1) for
the estimation of Hayabusa2 trajectory. In principle, LIDAR data gives information on the radial direction
and AIT data give the ones on the across and along track directions. Thus, both data sets are
complementary and help to improve the precision of the trajectory estimation. For this purpose, we
improved c5 ++ so that it can deal with AIT data as observation data. In the presentation, we will show the
results of trajectory and GM estimations using LIDAR and AIT data, and show how much the precision and
accuracy are improved compared to the case using LIDAR data only. 
Hayabusa2, Orbit Determination, Ryugu 
PPS03-P20Japan Geoscience Union Meeting 2019
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