Method for retrieval of atmospheric water vapor using OH airglow for correction of astronomical observations

Xu, Jing; Liu, Wenjuan; Bian, Jianchun; Liu, X.; Yuan, Wei; Wang, C.

doi:10.1051/0004-6361/201834621

Cited by 3 publications

(2 citation statements)

References 19 publications

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“…However, as the L‐HATPRO data set starts in 2014 and shows several gaps afterward, we mostly used these data to calibrate intensity ratios of lines with low and high transmission in the bands OH(2–0) and OH(6–4) to estimate PWV values for each spectrum (cf. Xu et al., 2020). Up to very high L‐HATPRO PWVs of about 16 mm, the approach works quite well with a mean offset of −0.1 mm and a standard deviation of 0.6 mm.…”

Section: Datamentioning

confidence: 99%

Effective Emission Heights of Various OH Lines From X‐Shooter and SABER Observations of a Passing Quasi‐2‐Day Wave

et al. 2022

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Chemiluminescent radiation of the vibrationally and rotationally excited hydroxyl (OH) radical, which dominates the nighttime near‐infrared emission of the Earth's atmosphere in wide wavelength regions, is an important tracer of the chemical and dynamical state of the mesopause region between 80 and 100 km. As radiative lifetimes and rate coefficients for collision‐related transitions depend on the OH energy level, line‐dependent emission profiles are expected. However, except for some height differences for whole bands mostly revealed by satellite‐based measurements, there is a lack of data for individual lines. We succeeded in deriving effective emission heights for 298 OH lines thanks to the joint observation of a strong quasi‐2‐day wave (Q2DW) in eight nights in 2017 with the medium‐resolution spectrograph X‐shooter at the Very Large Telescope at Cerro Paranal in Chile and the limb‐sounding SABER radiometer on the TIMED satellite. Our fitting procedure revealed the most convincing results for a single wave with a period of about 44 hr and a vertical wavelength of about 32 km. The line‐dependent as well as altitude‐resolved phases of the Q2DW then resulted in effective heights which differ by up to 8 km and tend to increase with increasing vibrational and rotation excitation. The measured dependence of emission heights and wave amplitudes (which were strongest after midnight) on the line parameters implies the presence of a cold thermalized and a hot non‐thermalized population for each vibrational level.

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Section: Datamentioning

confidence: 99%

Effective Emission Heights of Various OH Lines From X‐Shooter and SABER Observations of a Passing Quasi‐2‐Day Wave

et al. 2022

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“…In addition, the emission of water vapor also increases the background, which reduces the observation sensitivitySilva et al (2010).Because water vapor undergoes rapid variations over time, both in different directions and at different locations, and because the line of sight to astronomical targets is constantly changing over time, water vapor along the line of sight significantly influences astronomical observations. Therefore, locally, along the line of sight, it is necessary to monitor water vapor in real time to correct astronomical observationsXu et al (2020).…”

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confidence: 99%

A 22 GHz Pseudo-correlation Water Vapor Radiometer.

Reeves

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The radiation that comes from celestial objects is affected by different atmospheric components, mainly by water vapor, which is a highly variable component. This molecule can scatter, absorb and re-emit radiation and, therefore, attenuate it, affecting astronomical observations. Water vapor radiometry is an accurate method to measure the water vapor content in the atmosphere and, at altitudes 4000 masl, the 22 GHz emission line is chosen to estimate the amount of water vapor present in the at the time of the astronomical observation. This instrument, which is under development at CePIA UdeC laboratory, will provide a notable improvement in the measurement of the line profile of water vapor and will allow atmospheric characterizations that can be validated with other instruments in places where this quantity is relevant. The architecture designed for this project corresponds to a self-calibrated instrument, heterodine and is based on the pseudo-correlation principle. It consists of three parts: frontend, where incoming the RF signal is at a frequency range of 20 - 26 GHz; analog backend, where the RF signal is converted to a manageable frequency range of 0 - 6 GHz, called Intermediate Frequency (IF); and finally, the digital backend where the IF signal is processed in real-time through FFT, with a high spectral resolution of 62.5 kHz; the spectrum is divided intro three bands of 2 GHz each, in different Nyquist zones. Each output of the spectrometer is directly proportional to the brightness temperature of the load or the input, that provides a stable output measurement over time.

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