OSIRIS Overview & Status:
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OSIRIS is a multi-purpose near-IR imager and spectrograph that has been used at the 4m Blanco telescope on Cerro Tololo and is now available at SOAR as a facility instrument. OSIRIS operates at wavelengths from 0.9 to 2.4 microns and uses a 1024×1024 HAWAII HgCdTe array. The instrument contains two reimaging cameras, f/2.8 and f/7, which provide two different plate scales. There is also a pupil viewing camera (a silicon lens) for aligning the pupil plane mask, which is designed to block thermal emission from the telescope secondary mirror.
Imaging Mode: OSIRIS can be placed into imaging mode by removing the grating from the beam and inserting the prefilter wheel and pupil mask into the optical path. Two 10 position filter wheels holding nine filters each can be used in imaging mode. These filter wheels contain a variety of broadband and narrow band NIR filters. The filters can be used with either of the reimaging cameras with the properties listed below.
OSIRIS Overview & Status (Cont):
Spectroscopic Mode: OSIRIS has three spectroscopic modes: low-resolution (R~1200) and high-resolution (R~3000) long slit modes plus a low-resolution cross-dispersed mode (R~1200) with a short slit. Separate slits are provided for each mode as described in the table below.
2The X-Disp slit has an integrated JHK filter to provide blocking outside of the bands of interest.
All spectroscopic modes use a diffraction grating blazed at 6.6 microns in 1st order, which places the K-band in 3rd order, the H-band in 4th order, and the J-band in 5th order. A grism and and JHK filter are used to cross-disperse orders 3,4, and 5 across the detector in X-Disp mode. The following table summarizes the basic properties of the OSIRIS spectroscopic modes.
1Assumes that the imaging masks restrict the field to 577×577 pixels.
(Left): DSS R-band image (about 5’ on a side) of the Galactic HII region Sharpless 307 (Sh 2-307). (Right): OSIRIS high-resolution J- (blue), H- (green) and Ks-band (red) three-color composite image (∼70 × 50 arcsec2) of the section delineated by the white dotted square in the R-band image. A cavity inside the cloud (delineated by the K-band emission) is clearly seen. In this figure, north is to the left and east is down. Image courtesy of A. Romen-Lopes.
The NIR spectrum of IRS1 superimposed on the J-, H-, and K-band spectra of the O9.5 V star HD123056, as obtained with OSIRIS in X-Disp mode. Spectra courtesy of A. Roman-Lopes.
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An internal view of OSIRIS that was taken during maintenance. OSIRIS is a multi-purpose imager and spectrometer built by the Ohio State University. It is currently deployed at SOAR as a facility IR instrument. OSIRIS operates at wavelengths from 0.9-2.4μm and uses a 1024×1024 HAWAII HgCdTe array supplied by CTIO.
OSIRIS on its handling cart in the SOAR electronics lab.
Ohio State Infra-Red Imager/Spectrometer
Information herein adapted from SOAR web pages.
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