Wide Field Infrared Camera (WIRC) Technical Specifications

View the original specs page.

Status: Observatory Instrument


    Contents

  1. Updates
  2. Documentation
  3. Telescope
  4. Detector
  5. Scale
  6. Filters
  7. Sensitivities
  8. Background
  9. Unresponsive pixels

1. Updates

April 2014

Optical schematic.

  1. Detector was replaced due to a catastrophic failure of the original H2.
  2. Some detector characteristics have changed (this will be updated as more information becomes available):
    • Quadrant 1 is non-uniform accros the channel.
    • The detector is linear is up to 21,000 adu.

August 2007

  1. The pickup noise in WIRC images has been eliminated. Read noise is now 12 e in a standard CDS image.
  2. The detector read mode has been changed from a global reset-read to a line by line reset-read. As a result, observers may notice two small differences:
    • A dark image has a stronger spatial signal gradient. This effect is stable and subtracts away.
    • The full frame exposure time is now 3.23 seconds, not 3.25.
    • The best linearity is between 3,000 adu and 36,000 adu.

2. Documentation

Please reference this SPIE paper: Full SPIE paper, PDF file.

3. Telescope

  • 200-inch prime focus, f/3.3.
  • Field of view: 8.7′ on a side.

4. Detector

  • 2048 × 2048 Hawaii-II HgCdTe.
  • Gain 5.467 e/adu.
  • Dark current: ~0.048 adu/s = ~0.26e/s
    (due to slight filter leak, dome must be dark when taking dark frames).
  • Read noise: 12 e.
  • Frame rate (shortest exposure time for full array): 3.23 seconds.

5. Scale

  • 0.2487″/pixel (residuals = rms 0.286″ RA and 0.296″ Dec).
  • The camera is rotated 1.39° relative to N and E directly along rows and columns.
  • This information is provided by Dave Thompson, see his email.

6. Filters (Standard Setup)

For an excellent set of WIRC filter transmission profiles put together by J. Wilson and L. Smith, U. of Virginia go to WIRC Filter Plots.

Filter Wheel Wheel Position Filter Wavelength Center Manufacturer
Fore Wheel F-1 Open
F-2 PG
F-3 Brγ 2.166 NDC Infrared
F-4 Diffuser
F-5 Fe II 1.644 NDC Infrared
F-6 H-cont 1.570 NDC Infrared
F-7 Grism
Aft Wheel A-1 K-cont 2.270 NDC Infrared
A-2 CO (0-2) 2.294 NDC Infrared
A-3 H2 2.120 NDC Infrared
A-4 Open
A-5 Ks 2.150 Barr Associates
A-6 H 1.635 OCLI
A-7 J 1.250 OCLI

7. Sensitivities

  • For one hour total integration in 1″ seeing for a point source (2″ diameter aperture):

    Filter S/N Magnitude Notes
    J 5 sig 22.0 photometric, 21-22mar03 å å (provided by Dave Thompson)
    Ksh 5 sig 20.6 photometric, 17sep02 å å (provided by Dave Thompson)
  • more sensitivity numbers

8. Background

This table will be updated periodically:

Filter Season DN/s/pix DN/s/arcsec2 Magnitude
J September (clear) 65å¡ 115 1840 14.6
J November (cirrus) 50å¡ 70 1120 15.2
J March (clear) 32å¡ 55 880 15.4
J April (clear) 40å¡ 58 928 15.4
J May (clear) 68å¡ 62 992 15.3
H September (clear) 65å¡ 270 4320 13.9
H May (clear) 71å¡ 320 5120 13.8
Ksh September (clear) 65å¡ 515 8240 12.8
Ksh September (clear) 64å¡ 680 10880 12.5
Ksh November (cirrus) 50å¡ 500 8000 12.8
Ksh March (clear) 32å¡ 390 6240 13.1
Ksh April (clear) 47å¡ 355 5680 13.2
Ksh April (clear) 51å¡ 422 6752 13.0
Ksh April (cirrus) 50å¡ 435 6960 13.0
Ksh May (clear) 68å¡ 750 12000 12.4
Brγ May (clear) 68å¡ 60 960 **
** Zero point not yet known

9. Unresponsive Pixels

  • 3 cooldown cycles between December 2002 and December 2003
  • 1 cooldown cycle between December 2003 and January 2004
  • This table will be updated periodically:
Quadrant Sep 2002 Oct 2002 Nov 2002 Dec 2002 Dec 2003 Jan 2004
Lower Left (1) 124 116 127 152 114 148
Lower Right (2) 664 686 693 752 715 739
Upper Left (3) 1247 1011 1104 1142 670 948
Lower Right (4) 3142 3109 3232 3572 3204 3307

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WIRC Specs / v 2.0
Last updated: 15 Mar 2017 CMH