NOTCam - an overview

NOTCam is a multi-mode instrument for use in the short-wave infrared (SWIR) region of the electromagnetic spectrum (0.8 - 2.5µm). It is based on the Rockwell Science Center "HAWAII" array with 1024×1024×18.5µm pixels in HgCdTe. NOTCam is capable of:

Wide field imaging (4'×4' @ 0.234"/pixel)

High resolution imaging (80"×80" @ 0.078"/pixel)

Low-resolution (R = 2500) WF-cam spectroscopy (Y,J,H,K)

Medium-resolution (R = 5500) HR-cam spectroscopy (J,H,K)

On entering the front window of the dewar, light passes through the following components before impinging on the detector ( engineering grade array (SWIR1) , first science grade array (SWIR2) , new science grade array (SWIR3) ):

the aperture wheel
- At the telescope focus, carries slits and masks. There are 4×50-mm and 8×18-mm slots.
the collimator
the shutter
- A rigid spinning disk.
two filter wheels
- Each with 16 slots of 25mm diameter allowing for the use of up to 30 filters.
the pupil wheel
- At a pupil plane, carries Lyot stops and other pupil masks. There are 16 slots.
the grism wheel
- Carries dispersing elements. There are 16 slots. Check NOTCam spectroscopy pages.
the lens wheel
- Carries two sets of imaging optics, one for each plate scale (the WF and HR cameras), and the pupil re-imager.

Since NOTCam is kept cold for long periods at a time, we do not change filters, slits, grisms etc. more often than absolutely necessary (see the current setup).

The original optical design is described here (pdf).

This entire assembly is mounted on an optical bench which is in thermal contact with an LN₂ tank. Additional cooling is provided by a pulse-tube refrigerator (PTR) from Iwatani. The optical bench is covered with a radiation shield and this and the LN₂ tank are surrounded by a superinsulating blanket. The final enclosure is the dewar skin which maintains a high-quality vacuum surrounding the instrument. More about Mechanics and Cryogenics.

Last modified: October 23 2023