[2017/3/3] 金星探査機「あかつき」搭載のIR1・IR2、科学観測を休止 (news)

金星探査機「あかつき」に搭載された5つのカメラのうちの1つ,IR1・IR2(近赤外線用)が,観測を休止しました.
http://www.isas.jaxa.jp/topics/000901.html

昨年12月翌12月10日以降,両カメラの電源が投入できない状態です.あかつきは長期間の寄り道をしてきた結果,2010年打上げ以降すでに7年を経過しており,機器劣化のためなのでしょう.2016年末の軌道投入成功以降,ようやくデータが蓄積されつつあるところで,残念です.

東北大では,私がIR2の共同研究者,坂野井がIR1の共同研究者です.IR2の検出器は,今年度で退任される天文専攻の市川先生ともども修士の際にいじり倒していた曰く付きのもの.(先日の市川先生の最終講義でいきなりその写真が登場.当時を思い出すとなんとも言いようがない気分です.)

とはいえ,ここまで1年間蓄積されてきたデータはあり,また今後も観測が続くUVI(紫外線)・LIR(中間赤外線)カメラの観測は続きます.うちのメンバーは,これらの観測解析を地上観測・数値シミュレーションと噛み合わせつつ,研究を継続して行く予定です.

Study of Sulfuric Acid Clouds using Venus General Circulation Model

Credit by ESA

Credit by ESA

Venusian sulfuric acid cloud deck exists in the altitude of 50km-70km. It is considered that this cloud affects atmospheric general circulation by reflecting and absorbing solar radiation and emitting heat. It is known that this cloud varies temporaly and spatially. I study the production/extinction system and distributions of  sulfuric acid clouds on general circulation of Venus’ atmosphere using Venus General Circulation Model (VGCM). Presently, I try to reproduce variations of sulfric acid vapor, and I want to reproduce radiation from sulfuric acid cloud and reveal the effect eventually.

(Kazunari Itoh)

Water cycle on Mars

地上望遠鏡による観測

Water cycle on Mars is one of the big issues because recently it is suggested that a large amount of ice exists under the soil. We investigate the map of isotopic ratio in water vapor by Subaru telescope and compare with the GCM model for understanding of water cycle on Mars. Also, we attempt to derive vertical profile of the water vapor. Very recent study shows super saturation of water vapor and it needs further research of its vertical profile. In future, we plan to do continuous observation of the trace gases with our developing infrared heterodyne spectrometer at our Hawaii Haleakala telescope.

Trace gases in the Martian atmosphere

Credit by ESA

Credit by ESA

We investigate methane(CH4), hydrogen peroxide(H2O2), and water vapor in the Martian atmosphere by the Planetary Fourier Spectrometer (PFS) onboard Mars Express spacecraft. Recently, methane is discovered in the Martian atmosphere. It is remarkable because its sources are potentially a geological and a biological activity on Mars. We observed Mars for constraint of the source of methane and the data analysis is on-going now. We attempt to derive vertical profile of methane with the PFS limb-geometry observation data. Hydrogen peroxide is one of the best tracers of oxidizer in the Martian atmosphere. We detected it by the PFS onboard MarsExpress. It was first time to detect hydrogen peroxide with an instrument onboard Mars explorer. The derived amount was very small (~40ppb), which is not enough to destroy methane in weeks or months. Since the observed lifetime of methane is weeks or months, is needs further research of the sink of methane.

CO2 cloud on Mars

Credit by ESA

Credit by ESA

In martian mesosphere, not only water-cloud, but also CO2-cloud exists. CO2-cloud was first observed by a spectroscopy onboard Mars Express. Until today, It is found that CO2-cloud have spatial and seasonal dependence , but detail of cloud itself is not clear. We use infrared fourier spectrometer PFS which have high-spectral resolution , and it could make cloud feature clear.

IR heterodyne spectroscopy

Haleakala

The laser heterodyne spectroscopy is the most sensitive and highest resolution spectroscopy (1E7-8) in the middle infrared region, and has been expected to be a powerful method for atmospheric studies. Fully resolved molecular features provided by applying heterodyne techniques are possible allowing retrieval of many physical parameters from single lines. Our group in Tohoku University has developed since 1985, and the terrestrial minor constituents and their vertical profiles have been investigated. From 2009, our infrared laser heterodyne spectroscopy has been developed with quantum cascade lasers (QCLs) which offer sufficient optical output power of several to hundreds milliwatts to guarantee an efficient heterodyne process and high system sensitivity for planetary study. This instrument will be onboard the dedicated PLANETS telescope and Tohoku-60cm  (T60) telescope at the top of Mt. Haleakala, Hawaii, in order to perform continuous monitoring of planetary atmospheres. Our equipment and T60 has been successfully moved to the summit on August 2014, thanks to the great collaboration with University of Hawaii (Jeff Kuhn, Joe Ritter, and their colleagues). T60 itself has been carefully setup by an excellent works of Mitaka-Koki. Our heterodyne is also almost ready to go. Thanks to many people, we are just in front of the first light of T60 and heterodyne instrument. (August 28 2014, Hiromu Nakagawa)