MIRAC - Mid-Infrared Array Camera - History 1988 - 2020

William F Hoffmann, whoffmann@as.arizona.edu; Joseph L Hora, jhora@cfa.harvard.edu
March 13, 2020

MIRAC (Mid-Infrared Array Camera) is the name given to an evolving sequence of Mid-Infrared Cameras built for astronomical observations in the wavelength bands at 3.6, 4.5, 8-14, and 17-25 μm. The instruments were built and maintained at Steward Observatory at The University of Arizona as a collaboration of several institutions. A brief description of each version of the camera is given followed by partial lists of 10 Ph.D. theses and 120 publications using data from observations with the cameras. The web search engine, Google Scholars, lists over 2000 MIRAC publications and citations from 1988 to 2020. Links to the original MIRAC user's manual and some sample images taken with the MIRAC1-2 systems are available on the old MIRAC page.

MIRAC-1, 1988-1994, was built in 1988-89 as a collaboration of William Hoffmann at The University of Arizona (UA), Giovanni Fazio at the Smithsonian Astrophysical Observatory (SAO), and Kandiah Shivanandan at the Naval Research Laboratory. It used a liquid helium cooled cryostat built by Infrared Labs and a Hughes 20x64 Si:As photoconductive 20 line readout array obtained from the Air Force Albuquerque Lab, the first device of this technology obtained for astronomy. The readout electronics were custom designed and built at SAO and the software was created by UA graduate student Joseph Hora. The camera was used primarily on the Steward Observatory 1.5-m and 2.3-m telescopes on Mt. Bigelow and Kitt Peak, respectively, and the NASA 3-m IRTF (Infrared Telescope Facility) on Mauna Kea in Hawaii for observations of solar system objects, young stellar objects, planetary nebulae, infrared-luminous galaxies, star forming regions, and brown dwarfs.

MIRAC-2, 1994-2000, was a collaboration of UA and SAO upgrading to a Rockwell 128x128 blocked impurity band (BIB) array, again one of the first in civilian hands. The upgrade was undertaken for NASA IRTF observations of the collision of the comet Shoemaker-Levy-9 with Jupiter in July 1994. It used the same cryostat and electronics with modifications, many carried out by the UA graduate student Aditya Dayal and with filters provided by Glenn Orton at JPL. Lynne Deutsch (NASA Ames, Boston University) contributed to creating scientific interest in using MIRAC across the astronomical community. Subsequently the camera was used mainly on the IRTF and UKIRT (United Kingdom Infrared Telescope) on Mauna Kea as a visitor instrument supporting programs of many astronomers for observations of planetary nebula, star forming regions, young stellar objects, the galactic center, infrared bright galaxies, QSO's, and a variety of solar system objects, including planets (Jupiter, Saturn, Mercury) and comets (Shoemaker-Levy-9, Hyakutake, Swift-Tuttle, Giacobin-Zinner, LINEAR, Hale-Bopp, and Swift-Tuttle).

MIRAC-3, 2000-2008, underwent modifications of the cryostat and optics to interface with the newly ungraded MMT single 6.5-m mirror. The first observations and publication from the upgraded MMT were by a University of Illinois graduate student using MIRAC3 and Public Access Time. For this work MIRAC was mated to BLINC (BracewelL Infrared Nulling Cryostat created by Philip Hinz) and achieved early astronomical stellar nulling observations. It was used in three campaigns on the Magellan telescope at the Las Campanas Observatory in Chile contributing to two student thesis projects. Subsequently, MIRAC3 was used mainly at the MMT.

MIRAC-4, 2008-2011, represented a major change with a new, larger cryostat with mechanical pulse-tube cooling, rather than liquid helium, new electronics, a duplicate of the electronics built by Cornell University for the FORCAST instrument on NASA's SOFIA Airborne Observatory, and a new 256x256 Si:As BIB array from the DRS company (which inherited the technical group from Rockwell). It was the first infrared camera cryostat completely built at Steward Observatory and was used as a prototype for NIC (Nulling Infrared Camera) of Philip Hinz on the Large Binocular Telescope (LBT). MIRAC-4 was used for the first demonstration of fringes from the two LBT apertures and was used successfully on the MMT for two graduate student projects. Unfortunately the detector had a manufacturing flaw which resulted in image artifacts which limited its usefulness for astronomy. We gave up using this detector as did other astronomical groups in the United States and Europe. MIRAC became dormant for several years.

MIRAC-5, 2018- , has been reactivated as a laboratory test chamber for new mid-infrared Mercury-Cadmium-Telluride 1024x1024 arrays from Teledyne Imaging Systems utilizing a GeoSnap and an H1RG readout. This effort is led by Jarron Leisenring assisted by Katie Morzinski, both at Steward Observatory. Our next step is to reconfigure the instrument for astronomical observations on the MMT and Magellan Telescopes with one of these new arrays in a collaborative effort with Michael Meyer and Dani Atkinson at the University of Michigan.

Ph.D. theses that used MIRAC 1-4 Data

(Inverse chronological order, 2016 - 1991)

Astronomical Publications of Results from MIRAC 1-4

(Inverse chronological order, 2018 - 1990)

Last updated: Monday, 16-Mar-2020 10:53:53 EDT