nir_spectroscopy_20230101

Observing

Available Modes†

Available spectroscopic modes are listed in the table below. To avoid saturation due to the strong emission from the diamond window, an ND filter with OD=2 is needed for observations in the LM band.

Saturation limit†

Saturation limits depend on wavelength as shown in the figures below, and the typical levels are summarized in the following table. In the water-vapor-absorbing bands, the saturation limits vary with PWV.

Saturation limit of the KL band mode.	Saturation limit of the 2.7um band mode.	Saturation limit of the LM+ND2 band mode.

Sensitivity†

1-sigma 1-sec sensitivity is shown in the figures below. Since the sensitivity is limited by readout noise (assumed 100e-/read), it improves with longer 1-frame exposure times. In water-vapor-absorbing bands, it also depends on PWV. The truncation on the right edge shows the saturated region with the corresponding exposure time. The LM-mode sensitivity is significantly worse due to the ND filters and the strong absorption of the diamond window.

KL mode†

KL-mode sensitivity at PWV=0.3 mm.	KL-mode sensitivity at PWV=0.7 mm.	KL-mode sensitivity at PWV=1.2 mm.

2.7-um mode†

2.7um-mode sensitivity at PWV=0.3 mm.	2.7umL-mode sensitivity at PWV=0.7 mm.	2.7um-mode sensitivity at PWV=1.2 mm.

LM+ND2 mode†

LM-mode (w/ ND2) sensitivity at PWV=0.3 mm.	LM-mode (w/ ND2) sensitivity at PWV=0.7 mm.	LM-mode (w/ ND2) sensitivity at PWV=1.2 mm.

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