Observation of greenhouse gases from ground-based infrared astronomical telescope Yoji Hayashi, Ryoichi Imasu Atmosphere and Ocean Research Institute, The University of Tokyo 林 洋司, 今須 良一 東京大学 大気海洋研究所 気候システム研究系 miniTAO Work Shop @天文学教育研究センター 2013/03/14

Atmospheric chemistry Objectives To develop a method for the estimation of green house gas concentrations from astronomical observation data. Solar TAO project A joint project among Institute of Astronomy, School of Engineering and AORI. To fill the observation blank area. Astronomy Device Database Observed data Analysis results Atmospheric physics Atmospheric chemistry Fig. Ground-based observation site for GHGs

Objectives To develop a method for the estimation of green house gas concentrations from astronomical observation data. To develop a method using currently available data from Subaru. Targeting on green house gases, such as ozone. Aiming for the analysis of CO2, CH4 in the future. Atmospheric observation using miniTAO telescope based on the experience from Subaru data analysis. Using existing facilities makes it needless to set up new observatories for atmospheric observation.

Flow chart Stellar spectrum absorbed by atmosphere 観測画像 整約済み画像 測光 撮像 画像整約 補正 切り出し 分光 強度 strength 波長 wavelength Original stellar spectrum Optical thickness radiance by Cohen et al. 1999 GHGs concentration wavelength

Analysis method z x RTE: star1 （１） I2’ I1’ RTE: star2 （２） Transmittance : （１）÷（２） θ1 θ2 Optical thickness:τ observed database observed I1 I2 x

Observation of standard star on 2006/01/13 ② ① ③ ⑥ ⑤ ④ ⑦

Analysis result on 2006/01/13 @9.6mm （ozone absorption band） 110±30DU Fig. Calculated optical thickness Fig. Relationship optical thickness to columnar Ozone 105±30DU Columnar Ozone observed by OMI on the same day: 200±50DU Underestimated compared to OMI. Systematic error in the method?? Unrecognized sources of error?? 0.53±0.07

Conditions for atmospheric observation using astronomical data Both method 1 and 2 need a sufficient angular difference between the two astronomical observation data sets. A sufficient angular difference should make the following term in the analytical equation less than 1. For example, if one zenith angle of the star is 30 degrees, the other should more than 65 degrees. White area: the above term is less than 1.

Case study on 2012/10/30 : Method 1. : Method 1. : Method 2. ② Method 1. Same star at different time. Method 2. Different star at same time. ① : Method 1. : Method 1. : Method 2.

Observation log on 2012/10/25 ① ② Time MAX File # Object Filter Focus Filter Exp. Time Image Size Altitude Memo 02:37 61176-61177 aOri -7.9 12.2 10 80x64 位置合わせ 61178-61181 50 観測 61182-61185 -7.7 8.9 61186-61187 128x128 61188-61189 128x16 61190-61219 NGL 500 44.1553 61220-61221 61222-61225 61226-61229 9.8 03:02 61230-61233 04:44 61360-61361 61362-61365 61366-61369 61370-61373 61374-61375 61376-61377 61378-61407 NLG 59.4977 61408-61409 61410-61413 61414-61417 05:09 61418-61421 ① ②

Problems of data analysis Bright lines could not be seen. Unable to perform wavelength corrections… Relationship between pixel and wavelength is undetermined. The sensitivity variation of imaging data. Unable to perform correction of slit efficiency… Absolute value of spectra is undetermined. Data analysis is still in progress…

Observed spectra ① ② 61190to61219 61378to61407 intensity intensity noise noise

Comparison of observed spectra with simulated spectrum intensity ① ② Simulated 1 Simulated transmittance

Summary A estimation method of GHGs concentrations from the observed astronomical data was established for the first time. Conditions suited for atmospheric observation were determined. Further development of the analysis method to improve its accuracy. The miniTAO data needs further analysis. The necessity of image transformation. The necessity of correction of sensitivity for imaging data. …