Mimir - A Near-Infrared Wide-Field Imager, Spectrometer, and Polarimeter

Mimir is the name (not acronym) for a facility-class infrared instrument built at our IAR lab and at Lowell Observatory. Mimir saw first light on the 1.8 meter Perkins telescope outside Flagstaff, Arizona on August 19, 2004. It is now one of two facility-class instruments in regular use on Boston University's Perkins Telescope Observatory (PTO) outside Flagstaff, Arizona.

Mimir is a multi-function instrument that covers a broad wavelength range and allows users to perform complex observations with a single instrument. The three main functions Mimir performs are imaging (much as a camera takes pictures), spectroscopy (decomposing infrared star light into its constituent colors), and polarimetry. (click here for the article describing Mimir in the December 2007 issue of PASP).

Mimir’s wavelength coverage is from 1 to 5 micro-meters, or from about twice the wavelength of green light to about ten times that wavelength. This near-infrared light passes through the earth’s atmosphere only in a few bands of wavelengths (click here to see a plot). These bands are identified by letters, running from the shortest wavelength band, called J, through H, K, L, and M.

Mimir is open for regular scheduling and use by certified PTO users. Mimir's schedule usage on the PTO for the current quarter may be found on the PTO web site .

Eye Candy - Example Images and Spectra

NEWS - (click links to see details)

Servicing: The PTO M1 and M2 mirrors were realuminized in the LDT chamber at Happy Jack by Lowell Observatory staff, receiving a superb new coating of 0.1um of Al. Mimir was opened and service between 8/10/22 and 8/13/22. In addition to swapping out the cold head, one filter in FW1 was found to be loose, as one of its hold-downs had worked free. This was fixed. The slit and decker unit was inspected and found to be fully functional when warm, though the slit "home" sensor again failed after cool-down. Vacuum pumping took place from 8/20/22 through 8/22/22. Cooldown proceeded from 8/19/22-8/26/22 in a normal fashion. All mechanisms function and the detector is fine. A new connection from the helium shed data logger computer to the helium compressor now allows remote starts after power failures.

Observing:

Hardware:

  • Slit has lost home limit sensing. Can be used, but carefully. Contact DPC or MH for work-arounds

Upgrades:

  • IZYJ (0.82-1.36um) spec filter, though not much light shortward of 1.0um (see A0V Star raw spectrum)
    • 2nd order (0.8-1.274um) has much higher grism efficiency than 1st order (~6x more), and higher than in JHK-spec mode for the short half of J-band. Useable down to about 0.95um. Looks wonderful at He 1.083um.
  • IZYJ-X-Spec mode, using SED grism as cross-disperser
    • Modified two slits to provide short (20 arcsec or 30 arcsec) heights for support of X-D spec mode (2011/07). See updated slit table.
  • K-band Imaging Polarimetry (K-Pol)

Software: IDL GUI-based reduction tools available :

  1. New Spectroscopy Reduction Cookbook, and new spectroscopy GUI tools (BRT - baseline removal tool; SCT - spectra combiner; SAT - spectrum annotator)
  2. MSP-BDP - Basic Data Processing
  3. MSP-WCT - Spec. Wavelength Calibration
  4. MSP-CCS - Clean and Coadd Spectra
  5. MSP-SXC - Spec. spectrum extractor
  6. MSP-ZHT - Zero Hop Tester (for polarimetry)
  7. MSP-PPOL - Polarimetry Analysis - updated to support K-Pol mode
  8. MSP-PPT - Polarimetry Plotting Tool

Proposals to use Mimir and the Perkins:

  • Next BU deadline will be in September '22, for observing during 2022-Q4 (Oct, Nov, Dec) .

Note: Mimir is generally unavailable for some of July and August for annual servicing.

Mimir consists of a large vacuum cryostat that contains lenses, filters, motors, and a large format near-infrared array detector. The lenses take light from the Perkins telescope and focus it onto the detector array. The optics and the detector must operate at low temperatures, so Mimir is kept cool by a helium gas closed-cycle refrigeration system.

All instrument adjustments are made within the cryostat using vacuum cryogenic stepper motors and gear systems. These are controlled by computers located in the warm control room. All control information and image data are conveyed via fiber optics between Mimir and its computers.

Institute for Astrophysical Research, and the Perkins Telescope Observatory, Boston University

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20220906 DPC