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

Earth, Planets and Space

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

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

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