TY - JOUR
T1 - Venus' clouds as inferred from the phase curves acquired by IR1 and IR2 on board Akatsuki
AU - Satoh, Takehiko
AU - Ohtsuki, Shoko
AU - Iwagami, Naomoto
AU - Ueno, Munetaka
AU - Uemizu, Kazunori
AU - Suzuki, Makoto
AU - Hashimoto, George L.
AU - Sakanoi, Takeshi
AU - Kasaba, Yasumasa
AU - Nakamura, Ryosuke
AU - Imamura, Takeshi
AU - Nakamura, Masato
AU - Fukuhara, Tetsuya
AU - Yamazaki, Atsushi
AU - Yamada, Manabu
N1 - Funding Information:
The authors are grateful to W. Markiewicz for useful discussions. The observations would not have been possible without the selfless assistance of the engineering staff and operations-support staff. Comments from A. Mallama and another knowledgeable reviewer were of great help to improve the manuscript. This study was carried out with the Grants-in-Aid for Scientific Research (A) ( 20227937 ) from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT). This study is also supported in part by the Research Fellowships of the Japan Society for the Promotion of Science for Young Scientists (for S.O.).
Publisher Copyright:
© 2014 Elsevier Inc.
PY - 2015/3/1
Y1 - 2015/3/1
N2 - 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.
AB - 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.
KW - Atmospheres, structure
KW - Infrared observations
KW - Photometry
KW - Radiative transfer
KW - Venus, atmosphere
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U2 - 10.1016/j.icarus.2014.10.030
DO - 10.1016/j.icarus.2014.10.030
M3 - Article
AN - SCOPUS:84910018750
SN - 0019-1035
VL - 248
SP - 213
EP - 220
JO - Icarus
JF - Icarus
ER -