ISAAC Spectroscopic Modes

ISAAC is equipped with 2 gratings, for low (Rs~500) and medium (Rs ~ 3000) resolution spectroscopy in both the SW and LW arms (s is the slit width in arcsec).

SW Spectroscopy - Low Resolution (SWS1-LR)

The pixel scale is 0.147 arcsec/pixel. The slit length is 120 arcsec.

SW Spectroscopy - Low resolution  

Spectral domain (µm)	Order	Detector spectral coverage  (µm)	Number of grating positions	R(2")	R(1")	R(0.6")	R(0.3")
0.98 - 1.1	5	0.29	1	270	550	900	1800
1.1 - 1.4	4	0.36	1	250	500	860	1700
1.42 - 1.82	3	0.48	1	250	500	840	1600
1.82 - 2.5	2	0.72	1	200	450	750	1500

Use the Exposure Time Calculator (ETC) for performance estimates.

SW Spectroscopy - Medium Resolution (SWS1-MR)

The pixel scale is 0.146 arcsec/pixel. The slit length is 120 arcsec.

SW Spectroscopy - Medium resolution

Spectral domain (µm)	Order	Detector spectral coverage  (µm)	Number of grating positions	R(2")	R(1")	R(0.6")	R(0.3")
0.98 - 1.1	5	0.046	3-4	1700	3400	5700	11500
1.1 - 1.4	4	0.059	5	1500	3100	5200	10500
1.4 - 1.82	3	0.079	5	1500	3000	5100	10000
1.82 - 2.5	2	0.122	6	1300	2600	4400	8900

Use the Exposure Time Calculator (ETC) for performance estimates.

LW Spectroscopy - Low Resolution (LWS3-LR)

The pixel scale is 0.146 arcsec/pixel. The slit length is 120 arcsec.

LW Spectroscopy - Low resolution

Spectral domain (µm)	Order	Detector spectral coverage  (µm)	Number of grating positions	R(2")	R(1")	R(0.6")	R(0.3")
2.55 - 4.2	1	1.4	1	180	360	600	1200
4.45 - 5.1	1	1.5	1	250	500	800	1600

Use the Exposure Time Calculator (ETC) for performance estimates.

LW Spectroscopy - Medium Resolution (LWS3-MR)

The pixel scale is 0.146 arcsec/pixel. The slit length is 120 arcsec.

LW Spectroscopy - Medium resolution

Spectral domain (µm)	Order	Detector spectral coverage  (µm)	Number of grating positions	R(2")	R(1")	R(0.6")	R(0.3")
2.55 - 4.2	1	0.255	6(5)	1000	2000	3300	6700
4.45 - 5.1	1	0.237	3	1500	3000	5000	10000

Use the Exposure Time Calculator (ETC) for performance estimates.