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Table 2 Key properties of the NIRAS, both the spectrometer and the detector are manufactured by HORIBA Scientific. Typical operational parameters are also shown

From: Temporal evolutions of \(\text {N}_2^+\) Meinel (1,2) band near \(1.5.\,\upmu \text {m}\) associated with aurora breakup and their effects on mesopause temperature estimations from OH Meinel (3,1) band

Specifications of the NIRAS
Spectrometer Czerny-Turner
Focal length 320 mm
\(\textit{F}\) number 4.1
Slit width 0.10 mm (0–2 mm, electrically controlled)
Etendue 0.014–\(0.017\,\text {cm}^2\)*sr
Field-of-view \(0.019^{\circ }\times 0.19^{\circ }\)
Detector InGaAs 1-D array
Pixel size 25 μm × 250 μm (\(\text {W} \times \text {H}\))
Number of pixel 1024
Operation temperature \(-52.0 \pm 0.2\,^{\circ }\text {C}\), thermoelectric cooling
Grating 600 lpmm 150 lpmm
Blaze wavelength 1500 nm 1200 nm
Spectral sampling 0.11 nm/pixel 0.50 nm/pixel
Spectral resolution \(\ge 0.42 \,\text {nm}\) \(\ge 1.9 \,\text {nm}\)
Spectral range 119 nm 510 nm
Observation setting of the NIRAS
Observation condition Syowa: SZA \(\ge 100^{\circ }\), Kiruna: SZA \(\ge 96^{\circ }\)
Center of field-of-view Syowa: local magnetic zenith (\(63.4^{\circ }\)), Kiruna: local zenith
Temporal resolution 30 s (exposure 29 s)
Data acquisition cycle 3 min: 1 dark frame and 5 sky frames
Airglow target OH Meinel (3,1) band with the 600-lpmm grating
Aurora target \(\text {N}^+_2\) Meinel band and \(\text {N}_2\) 1st positive band with the 150-lpmm grating
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