Limaye Sanjay S, Watanabe Shigeto, Yamazaki Atsushi, Yamada Manabu, Satoh Takehiko, Sato Takao M, Nakamura Masato, Taguchi Makoto, Fukuhara Tetsuya, Imamura Takeshi, Kouyama Toru, Lee Yeon Joo, Horinouchi Takeshi, Peralta Javier, Iwagami Naomoto, Hashimoto George L, Takagi Seiko, Ohtsuki Shoko, Murakami Shin-Ya, Yamamoto Yukio, Ogohara Kazunori, Ando Hiroki, Sugiyama Ko-Ichiro, Ishii Nobuaki, Abe Takumi, Hirose Chikako, Suzuki Makoto, Hirata Naru, Young Eliot F, Ocampo Adriana C
1Space Science and Engineering Center, University of Wisconsin, Madison, WI 53706 USA.
2Space Information Center, Hokkaido Information University, Ebetsu, Hokkaido 069-8585 Japan.
Earth Planets Space. 2018;70(1):24. doi: 10.1186/s40623-018-0789-5. Epub 2018 Feb 12.
Since insertion into orbit on December 7, 2015, the Akatsuki orbiter has returned global images of Venus from its four imaging cameras at eleven discrete wavelengths from ultraviolet (283 and 365 nm) and near infrared (0.9-2.3 µm), to the thermal infrared (8-12 µm) from a near-equatorial orbit. The Venus Express and Pioneer Venus Orbiter missions have also monitored the planet for long periods but from polar or near-polar orbits. The wavelength coverage and views of the planet also differ for all three missions. In reflected light, the images reveal features seen near the cloud tops (~ 70 km altitude), whereas in the near-infrared images of the nightside, features seen are at mid- to lower cloud levels (~ 48-60 km altitude). The dayside cloud cover imaged at the ultraviolet wavelengths shows morphologies similar to what was observed from Mariner 10, Pioneer Venus, Galileo, Venus Express and MESSENGER. The daytime images at 0.9 and 2.02 µm also reveal some interesting features which bear similarity to the ultraviolet images. The nighttime images at 1.74, 2.26 and 2.32 µm and at 8-12 µm reveal features not seen before and show new details of the nightside including narrow wavy ribbons, curved string-like features, long-scale waves, long dark streaks, isolated bright spots, sharp boundaries and even mesoscale vortices. Some features previously seen such as circum-equatorial belts (CEBs) and occasional areal brightenings at ultraviolet (seen in Venus Express observations) of the cloud cover at ultraviolet wavelengths have not been observed thus far. Evidence for the hemispheric vortex organization of the global circulation can be seen at all wavelengths on the day- and nightsides. Akatsuki images reveal new and puzzling morphology of the complex nightside cloud cover. The cloud morphologies provide some clues to the processes occurring in the atmosphere and are thus, a key diagnostic tool when quantitative dynamical analysis is not feasible due to insufficient information.
自2015年12月7日进入轨道以来，“拂晓”号轨道飞行器已从其四个成像相机获取了金星的全球图像，这些图像涵盖了从紫外线（283和365纳米）、近红外线（0.9 - 2.3微米）到热红外线（8 - 12微米）的11个离散波长，其轨道接近赤道。“金星快车”和“先驱者金星轨道器”任务也对该行星进行了长期监测，但它们的轨道是极地或近极地轨道。这三项任务对该行星的波长覆盖范围和观测视角也各不相同。在反射光下，图像揭示了云顶附近（约70千米高度）可见的特征，而在夜侧的近红外图像中，可见的特征处于云层中下部（约48 - 60千米高度）。在紫外线波长下拍摄的日侧云层覆盖图像显示出与“水手10号”、“先驱者金星”、“伽利略号”、“金星快车”和“信使号”观测到的形态相似。0.9和2.02微米处的白天图像也揭示了一些与紫外线图像相似的有趣特征。1.74、2.26和2.32微米以及8 - 12微米处的夜间图像揭示了前所未见的特征，并展示了夜侧的新细节，包括狭窄的波浪状带、弯曲的线状特征、长尺度波、长长的暗条纹、孤立的亮点、清晰的边界，甚至中尺度涡旋。一些先前可见的特征，如赤道环带（CEBs）以及在紫外线波长下云层覆盖偶尔出现的区域增亮现象（在“金星快车”观测中可见），目前尚未被观测到。在日侧和夜侧的所有波长上都能看到全球环流半球涡旋组织的证据。“拂晓”号的图像揭示了复杂夜侧云层覆盖的新的且令人困惑的形态。云层形态为大气中发生的过程提供了一些线索，因此，当由于信息不足而无法进行定量动力学分析时，它是一种关键的诊断工具。
