Optimizing hydroxyl airglow retrievals from long-slit astronomical spectroscopic observations
Astronomical spectroscopic observations from ground-based telescopes contain background emission lines from the terrestrial atmosphere's airglow. In the near infrared, this background is composed mainly of emission from Meinel bands of hydroxyl (OH), which is produced in highly excited vibr...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-08-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/10/3093/2017/amt-10-3093-2017.pdf |
| Summary: | Astronomical spectroscopic observations from ground-based
telescopes contain background emission lines from the terrestrial
atmosphere's airglow. In the near infrared, this background is composed
mainly of emission from Meinel bands of hydroxyl (OH), which is produced in
highly excited vibrational states by reduction of ozone near 90 km. This
emission contains a wealth of information on the chemical and dynamical state
of the Earth's atmosphere. However, observation strategies and data reduction
processes are usually optimized to minimize the influence of these features
on the astronomical spectrum. Here we discuss a measurement technique to
optimize the extraction of the OH airglow signal itself from routine J-, H-,
and K-band long-slit astronomical spectroscopic observations. As an
example, we use data recorded from a point-source observation by the Nordic
Optical Telescope's intermediate-resolution spectrograph, which has a spatial
resolution of approximately 100 m at the airglow layer. Emission spectra
from the OH vibrational manifold from <i>v</i>′ = 9 down to <i>v</i>′ = 3, with
signal-to-noise ratios up to 280, have been extracted from 10.8 s
integrations. Rotational temperatures representative of the background
atmospheric temperature near 90 km, the mesosphere and lower thermosphere
region, can be fitted to the OH rotational lines with an accuracy of around
0.7 K. Using this measurement and analysis technique, we derive a rotational
temperature distribution with <i>v</i>′ that agrees with atmospheric model
conditions and the preponderance of previous work. We discuss the derived
rotational temperatures from the different vibrational bands and highlight
the potential for both the archived and future observations, which are at
unprecedented spatial and temporal resolutions, to contribute toward the
resolution of long-standing problems in atmospheric physics. |
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| ISSN: | 1867-1381 1867-8548 |