1. 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 2013/03/14

2. 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

3. 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.

4. 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

5. 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

6. Observation of standard star on 2006/01/13② ① ③ ⑥ ⑤ ④ ⑦

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

8. 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.

9. 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.

10. Observation log on 2012/10/25 ① ② Time MAX File # Object Filter
Focus
Filter
Exp. Time
Image Size
Altitude
Memo
02:37
aOri
-7.9
12.2 10
80x64
位置合わせ 50 観測
-7.7
8.9
128x128
128x16
NGL
500
9.8
03:02
04:44
NLG
05:09 ① ②

11. 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…

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

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

14. 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. …