ISAAC is an infrared (1 - 5 μm) imager and spectrograph mounted on the Nasmyth A focus of UT3. It has two independent arms, one equipped with a 1024 x 1024 Hawaii Rockwell array and the other with a1024 x 1024 InSb Aladdin array from Santa Barbara Research Center. The Hawaii arm is used at short wavelengths (1 - 2.5μm). The Aladdin arm is used predominantly at long wavelengths (3 -5 μm) but is also available for short wavelength imaging with broadband filters. Below we summarize in two tables the operational modes and predicted performance of ISAAC. Those tables are intended as a quick feasibility references only: proposers should refer to the detailed information (e.g. User's Manual, Exposure Time Calculator).All instrument modes are offered in both Visitor Mode and in Service Mode).
|Instrument Mode||Scale||FOV||limit magnitude|
|SW Imaging||0.148||152 x 152||J=24, H=23, Ks=22|
|SW Polarimetry||0.148||3 x 20 x 150||J=23, H=22, Ks=21|
|LW Imaging||0.071||73 x 73||L~16, M_NB ~ 13|
|LW Imaging 3.21, 3.28μm||0.148||152 x 152||L ~16|
 In polarimetry the FOV consists of three non-overlapping strips each of 20 x 150 arcsec^2.
The limit magnitudes in the table are the J (1.25μm), H(1.65μm), Ks (2.2μm), and L (3.8μm) background limited magnitudes for a point source which would give a S/N of 5 in one hour of typical background conditions and a seeing FWHM of 0.65''. In addition to the standard J, H, Ks, and L broadband filters, ISAAC is equipped with a wide selection of narrow bands (typically =0.015μm) filters. It is not possible to observe with ISAAC with user supplied filters.
|Instrument Mode||λ/Δλ||Scale||limit magnitude range|
|SW LRes Spectroscopy||500||0.147||18-20.5|
|SW MRes Spectroscopy||3000||0.147||17.5-19.5|
|LW LRes Spectroscopy||500||0.147||11-14|
|LW MRes Spectroscopy||2000||0.147||10-13|
The limit magnitudes given in the above table are the short wavelength (SW) and long wavelength (LW) magnitudes of a point source spectrum which would give a S/N of 5 per resolution element in the continuum in one hour under typical background conditions, seeing FWHMof 0.65'', and using a 1.0'' slit. Limits on IR spectroscopic capabilities vary strongly with wavelength due to the absorption/emission spectrum of the atmosphere, the range of limit magnitudes given in the table reflects this variation.