Ultraviolet imager on Venus orbiter Akatsuki and its initial results

Atsushi Yamazaki, Manabu Yamada, Yeon Joo Lee, Shigeto Watanabe, Takeshi Horinouchi, Shin ya Murakami, Toru Kouyama, Kazunori Ogohara, Takeshi Imamura, Takao M. Sato, Yukio Yamamoto, Tetsuya Fukuhara, Hiroki Ando, Ko ichiro Sugiyama, Seiko Takagi, Hiroki Kashimura, Shoko Ohtsuki, Naru Hirata, George L. Hashimoto, Makoto SuzukiChikako Hirose, Munetaka Ueno, Takehiko Satoh, Takumi Abe, Nobuaki Ishii, Masato Nakamura

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)


The ultraviolet imager (UVI) has been developed for the Akatsuki spacecraft (Venus Climate Orbiter mission). The UVI takes ultraviolet (UV) images of the solar radiation reflected by the Venusian clouds with narrow bandpass filters centered at the 283 and 365 nm wavelengths. There are absorption bands of SO2 and unknown absorbers in these wavelength regions. The UV images provide the spatial distribution of SO2 and the unknown absorber around cloud top altitudes. The images also allow us to understand the cloud top morphologies and haze properties. Nominal sequential images with 2-h intervals are used to understand the dynamics of the Venusian atmosphere by estimating the wind vectors at the cloud top altitude, as well as the mass transportation of UV absorbers. The UVI is equipped with off-axial catadioptric optics, two bandpass filters, a diffuser installed in a filter wheel moving with a step motor, and a high sensitivity charge-coupled device with UV coating. The UVI images have spatial resolutions ranging from 200 m to 86 km at sub-spacecraft points. The UVI has been kept in good condition during the extended interplanetary cruise by carefully designed operations that have maintained its temperature maintenance and avoided solar radiation damage. The images have signal-to-noise ratios of over 100 after onboard desmear processing. [Figure not available: see fulltext.].

Original languageEnglish
Article number23
JournalEarth, Planets and Space
Issue number1
Publication statusPublished - Dec 1 2018


  • Initial results of cloud tracking
  • UV images of Venus at the cloud top altitude
  • UVI performance
  • Ultraviolet imager (UVI)
  • Venus orbiter Akatsuki

ASJC Scopus subject areas

  • Geology
  • Space and Planetary Science


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