MIRAC3: A Mid-Infrared Array Camera
NOTE: This page describes the MIRAC3 instrument which has been decommissioned.
If you are looking for documentation on the current MIRAC instrument, see
the MIRAC4 and BLINC documentation page.
MIRAC3 was a Mid-InfraRed Array Camera built for ground based
astronomy at Steward Observatory, University of Arizona and Harvard-
Smithsonian Center for Astrophysics. (The instrument has been decommissioned,
the current instrument being operated is "MIRAC4"). It utilized a
128x128 arsenic-doped silicon blocked-impurity-band hybrid array
operating in a liquid helium-cooled cryostat at 5 K. It had an
operating wavelength range of 2 to 26 μm. Using 16 parallel readout
lines giving a frame rate up to .92 kHz, the array provided both low
noise and good linearity at high background flux, which are
essential for 10 and 20 μm ground-based observing conditions.
The array has a peak quantum efficiency of approximately 0.42 at 22
μm, and a linear well size of 3x107 electrons. The quantum
efficiencies at 2.2, 5, and 10 μm are approximately .05, .25, and
.30, respectively. The system has been used at
Observatory 2.3 meter telescope at
Kitt Peak, the
Magellan telescope on Las Campanas,
and at the IRTF
telescopes on Mauna Kea.
Optics and filters
Reflective optics in the camera
cryostat provide achromatic
diffraction-limited imaging at a nominal scale on IRTF of .34
arcsec/pixel (lambda/2D at 10 μm) and a maximum field size of 44x44
arcsec. The camera cryostat contains two cold filter
wheels with a 16% bandwidth filters at 2.2, 3.8. and 4.8 μm, a 4%
bandwidth filter at 7.9 μm, 10% bandwidth filters at 8.8, 9.8, 10.3,
11.7, and 12.5 μm, 2.6% bandwidth filters at 17.4 and 17.8 μm, 10%
bandwidth filter at 18.0 μm, 7% bandwidth filter at 20.6 μm, and an
N-band filter (8.1 - 13.1 μm).
A pupil slide provides for focal ratios of f/15,
f/16, f/32, f/36, and f/45 for the MMT, SOFIA, CTIO 4-meter,
IRTF/UKIRT, and Steward Observatory 2.3-meter telescopes.
The filter transmission and calibration was published in Mamajek et al. (2004; ApJ, 612, 496). See Eric's web page for the transmission curves and other info.
Electronics and computer
Digital and analog electronics mounted at the cryostat provide for
single and double read with a minimum pixel sample time of 1.07 usec
and a minimum full array read time of 1.09 msec. The array can be
read out in continuous or burst mode, with frame time (on-chip
integration time) up to 256 read times. Hard-wired arithmetic units
provide for fast coadding of up to 4095 frames before sending the
images via an optical fiber to a digital array processor (DSP) in a
Pentium PC. A sub-portion of the array in units of 32x32 pixels can
be chosen for coadding and transmitting to the PC. Full array
coimages can be sent to the DSP at a rate of 56 Hz and 1/16 of the
array at a rate of 800 Hz. The camera controller generates the
telescope secondary chopper motion and wait times synchronously with
the read and frame times. The PC and array processor control the
data acquisition, storage, processing and display, and initiate
telescope motions via ethernet or RS232. The data can be stored
both on the PC hard disk and on a facility computer disk via the
is available for processing the files stored in MIRAC
format, combining the chop and nod images, applying a mask and flat
fielding corrections, and producing image files in FITS format.
Typical sensitivities expected at IRTF are
26 mJy/arcsec2 at 11.7 μm (10% bandwidth
filter) and 100
mJy/arcsec2 at 20.6 μm
(6.8% bandwidth filter), all
chop-nod, one minute total observing time, with the source in one of four
The MIRAC camera was built as a collaborative effort among the University of
Arizona Steward Observatory (William F. Hoffmann and Joseph L. Hora), the Smithsonian Astrophysical Observatory (Giovanni G. Fazio, Lynne K. Deutsch), and
the Naval Research Laboratory (K. Shivanandan).
BLINC (Bracewell Infrared Nulling Cryostat) was built by Steward Observatory
(Hinz, R. Angel, N. Woolf, Hoffmann, & D. McCarthy). The MIRAC camera has
undergone several upgrades (see the History link below).
The camera system is currently
operated by Phil Hinz and
Hoffmann at Steward Observatory.
History of MIRAC
Examples of MIRAC Results
The MIRAC3 camera has been decommissioned. A new camera is currently in use
at the MMT, "MIRAC4". Contact Phil Hinz at Steward Observatory, University
of Arizona, for the most current information.
This is the complete manual for the MIRAC3 camera, dated
May 22, 1999. Read the
file about this distribution.
- Full manual in PDF format -
The full manual is available in pdf format. See the
Adobe home page for more information
about this format and
obtain a free pdf viewer (Acrobat reader).
- Postscript format manual parts -
The document is in gzipped postscript format files
and is available via anonymous ftp from
Obtaining and Reducing MIRAC Data
- "MIRAC2, a mid-infrared array camera for astronomy",
Hoffmann, W. F., Hora, J. L., Fazio, G. G., Deutsch, L. K., & Dayal, A.
1998, in Infrared Astronomical Instrumentation, ed. A. M. Fowler,
Proc. SPIE 3354, 647-658
- ``Nulling interferometry using the MMT'', P. Hinz, J. R. P. Angel,
D. W. McCarthy, Jr., W. F. Hoffmann, N. J. Woolf, J. L. Hora, 1998,
in Astronomical Interferometry,
ed. R. Reasenberg, Proc. SPIE 3350
- "MIRAC, a Mid Infrared Array Camera for Astronomy",
Hoffmann, W. F., Fazio, G. G., Shivanandan, K., Hora, J. L., & Deutsch, L. K.
1993, in Infrared Detectors and Instrumentation, ed. A. M. Fowler,
Proc. SPIE 1946, 449
- "Astronomical Observations with the Mid-Infrared Array Camera,
W. F. Hoffmann, G. G. Fazio, K. Shivanandan, J. L. Hora, & L. K. Deutsch
1994, Infrared Phys. Technol., 35, 175
A New Mid-Infrared Camera for Ground-Based Astronomy and An Infrared Study of
Planetary Nebulae", Hora, J. L, 1991, Ph.D. Dissertation,
University of Arizona
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Last updated: Wednesday, 27-Mar-2019 16:13:51 EDT