Preflight Calibration Test Results for Optical Navigation Camera Telescope (ONC-T) Onboard the Hayabusa2 Spacecraft
The optical navigation camera telescope (ONC-T) is a telescopic framing camera with seven colors onboard the Hayabusa2 spacecraft launched on December 3, 2014. The main objectives of this instrument are to optically navigate the spacecraft to asteroid Ryugu and to conduct multi-band mapping the asteroid. We conducted performance tests of the instrument before its installation on the spacecraft. We evaluated the dark current and bias level, obtained data on the dependency of the dark current on the temperature of the charge-coupled device (CCD). The bias level depends strongly on the temperature of the electronics package but only weakly on the CCD temperature. The dark-reference data, which is obtained simultaneously with observation data, can be used for estimation of the dark current and bias level. A long front hood is used for ONC-T to reduce the stray light at the expense of flatness in the peripheral area of the field of view (FOV). The central area in FOV has a flat sensitivity, and the limb darkening has been measured with an integrating sphere. The ONC-T has a wheel with seven bandpass filters and a panchromatic glass window. We measured the spectral sensitivity using an integrating sphere and obtained the sensitivity of all the pixels. We also measured the point-spread function using a star simulator. Measurement results indicate that the full width at half maximum is less than two pixels for all the bandpass filters and in the temperature range expected in the mission phase except for short periods of time during touchdowns.
KeywordsONC Visible Multi-band imaging Asteroid Hayabusa2 Ryugu
The authors wish to thank Dr. S. Nakazawa, Dr. Y. Tsuda, Dr. K. Ogawa, and Hayabusa2 team for supporting our calibration test. The authors also wish to thank Dr. Y. Iijima for supporting our activities.
- A.S. Rivkin, E.S. Howell, F. Vilas, L.A. Lebofsky, Hydrated minerals on asteroids: the astronomical record, in Asteroids III, ed. by W. Bottke, A. Cellino, P. Paolicchi, R.P. Binzel (University of Arizona Press, Tucson, 2004), pp. 235–253 Google Scholar
- S. Sugita, T. Morota, S. Kameda, R. Honda, C. Honda, Hayabusa-2 ONC Science Team, Science observations strategy for HAYABUSA-2 optical navigation cameras (ONC), in Lunar Planet. Sci. Conf., vol. XXXXIII, #3026 (2013), p. 2 Google Scholar
- S. Tachibana, M. Abe, M. Arakawa, M. Fujimoto, Y. Iijima, M. Ishiguro, K. Kitazato, N. Kobayashi, N. Namiki, T. Okada, R. Okazaki, H. Sawada, S. Sugita, Y. Takano, S. Tanaka, S. Watanabe, M. Yoshikawa, H. Kuninaka, The HAYABUSA2 Project TEAM, Hayabusa2: scientific importance of samples returned from C-type near-earth asteroid (162173) 1999 JU3. Geochem. J. 48, 571 (2014) CrossRefGoogle Scholar