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Filters

A list of the Michelle broad and narrow-band filters is presented here. Since the filter wheel is common to both the imaging and the spectroscopic light paths the filters are available in both modes. The longpass filters are used for lowN and MedN1 spectroscopy, while the narrow-band filters are used with the higher-resolution modes (all spectroscopy filter selection is done internally by Michelle and need not be specified by the PI). Transmission data are available for some filters, as indicated.

Detector Information

Michelle contains the same detector as T-ReCS. Some basic characteristics of the detectors are shown in the table below:

Spectroscopy

Basic characteristics of Michelle's spectroscopy modes

Michelle is capable of spectroscopy with R~100 - 30,000 in the 7 - 25 micron range as follows:

 

Entrance Window

Michelle uses an entrance window made of Potassium Bromide (KBr). KBr has a transmission of ~90% across the mid-infrared. Since KBr is hygroscopic, all contact between water with the window must be minimized. This includes dew that may form on the window while observing under high humidity conditions. The humidity limit for observing with Michelle at Gemini is a relative humidity of 80%. During its use at UKIRT, a protective "sacrificial window" system was implemented to help prevent damage to the cryostat window that serves as the vacuum seal between the dewar and the atmosphere.

Detector Information

Michelle contains the same detector as T-ReCS. Some basic characteristics of the detectors are shown in the table below:

Imaging

The properties of NIRI in imaging mode are summarized in the following sections. Three selectable fields of view and pixel scales are available. With adaptive optics NIRI is available at f/32 for J-L' imaging (but see caveats for L'), and at f/14 for imaging out to 2.5 microns due to the increased thermal background. Imaging at L' is impossible at f/6 and only sometimes possible at f/14. The narrow band L filters (e.g., the PAH filter, Br alpha) can be observed at f/32, f/14, and f/6. M' imaging is only possible at f/32.

NIRI

Overview of NIRI's Capabilities

Gemini's Near InfraRed Imager and Spectrometer, NIRI, was built by the University of Hawaii's Institute for Astronomy. It provides a range of imaging and spectroscopy options in the 1-5 micron wavelength region.

NIRI's detector is a 1024x1024 ALADDIN InSb array. The instrument has three cameras: f/32, f/14, and f/6. In imaging mode they provide plate scales of 0.022, 0.050, and 0.117 arcsec pixels, respectively and fields of view of 22x22, 51x51, and 120x120 arcseconds squared, respectively.

Observing with Gemini

How to observe with Gemini. Is this better as an expanded menu with a lot of items, as it is now (broken up by headings for Phase I and Phase II), or with just 3 expandable subheadings beneath it, or broken into two categories (phases 1 and 2) at the top level?

Imaging

Basic characteristics of Michelle's imaging mode

  • Several medium and narrow-band 10 um and 20 um filters (chop and nod)
  • Image FWHM at or approaching the diffraction limit (FWHM ~ 1.22 lambda/D ~ 0.31" at 10 microns, ~0.63" at 20 microns)
  • Pixel dimension = 0.1005" (imaging only)
  • Field of view = 32"x24" in imaging mode (but note that current maximum chop throw is 15")
  • Imaging usually not available using the broad band N and Q filters, due to detector saturation