Venus' clouds as inferred from the phase curves acquired by IR1 and IR2 on board Akatsuki

Takehiko Satoh, Shoko Ohtsuki, Naomoto Iwagami, Munetaka Ueno, Kazunori Uemizu, Makoto Suzuki, George L. Hashimoto, Takeshi Sakanoi, Yasumasa Kasaba, Ryosuke Nakamura, Takeshi Imamura, Masato Nakamura, Tetsuya Fukuhara, Atsushi Yamazaki, Manabu Yamada

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)


We present phase curves for Venus in the 1-2μm wavelength region, acquired with IR1 and IR2 on board Akatsuki (February-March 2011). A substantial discrepancy with the previously-published curves was found in the small phase angle range (0-30°). Through analysis by radiative-transfer computation, it was found that the visibility of larger (~1μm or larger) cloud particles was significantly higher than in the standard cloud model. Although the cause is unknown, this may be related to the recently reported increase in the abundance of SO2 in the upper atmosphere. It was also found that the cloud top is located at ~75km and that 1-μm particles exist above the cloud, both of these results being consistent with recent studies based on the Venus Express observations in 2006-2008. Further monitoring, including photometry for phase curves, polarimetry for aerosol properties, spectroscopy for SO2 abundance, and cloud opacity measurements in the near-infrared windows, is required in order to understand the mechanism of this large-scale change.

Original languageEnglish
Pages (from-to)213-220
Number of pages8
Publication statusPublished - Mar 1 2015


  • Atmospheres, structure
  • Infrared observations
  • Photometry
  • Radiative transfer
  • Venus, atmosphere

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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