ISAAC covers the 1-5µm wavelength range and is capable of:
- 1-2.5 µm imaging over a 2.5 arcmin x 2.5 arcmin field.
- 1-2.5 µm imaging polarimetry over a 2.5 arcmin x 2.5 arcmin field.
- 1-2.5 µm long slit low (Rs ~ 500) and medium resolution (Rs ~ 3000) spectroscopy
- 2.5-5 µm imaging over a 1.25 arcmin x 1.25 arcmin field.
- 2.5-5 µm long slit low (Rs ~ 500) and medium resolution (Rs ~ 3000) spectroscopy
Fig. 1 shows the optical layout of ISAAC. At the top and bottom are two cameras which are optimized for the 1-2.5µm and 2-5µm ranges and used to either re-image the telescope focal plane or the intermediate spectrum produced by the grating spectrometer. The short wave camera is equipped with a Rockwell Hawaii 1024x1024 pixel Hg:Cd:Te array and the long wave camera with an SBRC Aladdin 1024x1024 pixel InSb array. The characteristics of the detectors are given in the following table.
|Detector||Format||Pixel size||Gain||Read Noise||Q.E|
|SW - Rockwell||1024 x 1024||18.5 microns||4.5 electrons/ADU||11 electrons||0.65|
|LW - Aladdin, SBRC||1024 x 1024||27 microns||7.8 electrons/ADU (DCR-HB, UCR)||40 electrons||0.80|
|8.7 electrons/ADU (DCR-LB)|
Given the extreme range of backgrounds, from 0.1 electrons/sec/pixel to 3,000,000 electrons/second/pixel, the LW and SW detectors are used with different readout modes.
|Detector||Readout Mode||Corresponding instrument modes||Linearity||Saturation*||Minimum DIT|
|Hawaii||Double Correlated Read||All SW imaging||99% @ 10,000 ADU||40,000 ADU||1.77s or 3.5451s|
|Hawaii||Non Destructive Read||All SW spectroscopy||99% @ 10,000 ADU||40,000 ADU||1.77s or 3.5451s|
|Aladdin||Uncorrelated Read High Bias||L, nb_M imaging and LR M band spectroscopy||90% @28,000 ADU||37,000 ADU||0.1073s|
|Aladdin||Double Correlated Read High Bias||All other modes that use chopping, and non-chopped imaging with NB_3.21 and NB_3.28||90% @28,000 ADU||37,000 ADU||0.2771s|
|Aladdin||Double Correlated Read Low Bias||All modes that do not use chopping except NB_3.21 and NB_3.28 non-chopped imaging||90% @16,000 ADU||21,000 ADU||0.3447s|
* Saturation is the number of counts above the bias.
This document was last updated: 2010-11-30