講演情報
[PPS05-P06]Enormous cloud cover as seen by Akatsuki/IR2 on the night-side disk of Venus
*佐藤 毅彦1,2、Vun Choon Wei2、佐藤 隆雄3、堀之内 武4、はしもと じょーじ5、McGouldrick Kevin6 (1.宇宙航空研究開発機構・宇宙科学研究所、2.総合研究大学院大学・宇宙科学専攻、3.北海道情報大学・経営情報学部、4.北海道大学・地球環境科学研究院 、5.岡山大学・理学部地球科学科、6.LASP, University of Colorado Boulder)
キーワード：
あかつきIR2、金星夜面、雲濃度
Night-side observations in transparency windows of CO2 atmosphere of Venus allow visualizing inhomogeneous clouds in ~50 to ~60 km altitudes. The IR2 camera on board Akatsuki captured such images at 1.735, 2.26, and 2.32 um wavelengths. In the IR2 night-side data, an enormous cloud of greater opacity and very sharp edge in the front (western end) is seen repeatedly. This feature seems to encircle the planet with a period of ~4.5 days (Peralta).
Although interesting, property of particles in this feature was not studied before due to difficulty of photometric measurements in IR2 night-side data. This difficulty comes from a combination of the intense day crescent and extended tail of IR2 point-spread function (multiple reflection in the detector is the cause). We have developed a technique to restore the contrast of the night-side data by deconvolution so that the photometric studies can be done with IR2 night-side data.
The data acquired on 18th and 27th August 2016 are analyzed. We have performed a series of radiative transfer computations to reproduce both 1.735- and 2.26-um opacities in this enormous cloud. Properties of the cloud partices will be presented and possible mechanism of this remarkable phenomenon will be discussed.
Although interesting, property of particles in this feature was not studied before due to difficulty of photometric measurements in IR2 night-side data. This difficulty comes from a combination of the intense day crescent and extended tail of IR2 point-spread function (multiple reflection in the detector is the cause). We have developed a technique to restore the contrast of the night-side data by deconvolution so that the photometric studies can be done with IR2 night-side data.
The data acquired on 18th and 27th August 2016 are analyzed. We have performed a series of radiative transfer computations to reproduce both 1.735- and 2.26-um opacities in this enormous cloud. Properties of the cloud partices will be presented and possible mechanism of this remarkable phenomenon will be discussed.