JpGU-AGU Joint Meeting 2017

Presentation information

[EJ] Poster

P (Space and Planetary Sciences) » P-PS Planetary Sciences

[P-PS06] [EJ] Results of Venus science with Akatsuki in orbit for 1.5 year

Sat. May 20, 2017 3:30 PM - 5:00 PM Poster Hall (International Exhibition Hall HALL7)

convener:Takehiko Satoh(Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency), Takeshi Horinouchi(Faculty of Environmental Earth Science, Hokkaido University), Masaru Yamamoto(Research Institute for Applied Mechanics, Kyushu University), Kevin McGouldrick(University of Colorado Boulder)

[PPS06-P17] Coordinated observation of Venus cloud top with Subaru and Akatsuki

*Takao M. Sato1, Hideo Sagawa2, Toru Kouyama3, Makoto Taguchi4, Yeon Joo Lee1, Javier Peralta1, Masahiro Takagi2, George HASHIMOTO5, Takehiko Satoh1, Yasumasa Kasaba6, Shohei Aoki7, Tetsuya Fukuhara4, Atsushi Yamazaki1, Takeshi Imamura8, Masato Nakamura1 (1.Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 2.Kyoto Sangyo University, 3.National Institute of Advanced Industrial Science and Technology, 4.Rikkyo University, 5.Okayama University, 6.Tohoku University, 7.Institut d’Aéronomie Spatiale de Belgique, 8.The University of Tokyo)

Keywords:Venus, atmosphere, Akatsuki, ground-based observation

The first sequential mid-infrared images taken by Longwave Infrared Camera (LIR) onboard Akatsuki after its insertion into Venus orbit on December 7, 2015 revealed that a planetary-scale bow-shaped structure exists at Venus cloud top and is fixed in a position above Aphrodite Terra. This structure has been suggested to result from an upward-propagating mountain gravity wave generated by the interaction of atmospheric flow with the topography (Fukuhara et al., 2017). Up to the present, small and large bow-shaped structures possibly originated from similar mechanism have been detected above various highlands.
In order to obtain a better understanding of the atmospheric dynamics at the cloud top including the newly discovered stationary structure, we carried out the coordinated observation with Subaru Telescope and Akatsuki on January 11-14, 2017. The Cooled Mid-Infrared Camera and Spectrometer (COMICS) mounted on Subaru Telescope was used to observe Venus at the solar phase angle of ~90° with the evening terminator in view by two narrow-band imaging (8.66 μm and 11.34 μm) and N-band (8-13 μm) low resolution (R~250) spectroscopy. During the period, Akatsuki was approaching to Venus and solar phase angle at sub-spacecraft point was increasing from 15° to 50° with the evening terminator in the field of view. It means that overlapping and simultaneous dayside observations were performed with LIR and Ultraviolet Imager (UVI).
The COMICS images at both wavelengths after high-pass filtering, although the data processing is still ongoing, clearly show that a bow-shaped structure distributed in the equatorial region appears above the highland named Maat Mons in the early night and survives through the observation period. It is noteworthy that a stationary structure similar to those discovered by LIR was also observed by another different instrument, COMICS. In addition, several streaks are also found to be distributed over the entire disk and some of them are not fixed to the topography. The images on January 14 have a horizontal Y-shape feature resembling that seen in UV.
In this presentation, we will show the processed images obtained by COMICS and compare them with simultaneously-acquired LIR and UVI images.