OSCIR Introduction

OSCIR is not being offered on Gemini in 2002A. In its place, the facility mid-IR imager/spectrometer T-ReCS will be commissioned and is expected to be available.

OSCIR is a mid-infrared (8-25µm) imager and low/medium-resolution (R=100-1000) spectrograph built at the University of Florida and NASA Marshall Space Flight Centre. It has previously been used on the IRTF, CTIO 4m and Keck II. We have arranged for its use as a loaned instrument on Gemini.

OSCIR uses a 128 x 128 Si:As IBC detector optimised for the wavelength range 8-25µm, with observations possible (albeit with very low quantum efficiency) at K (2.2µm) and M (4.8µm) e.g. for target acquisition. On Gemini, OSCIR has a plate scale of about 0.084 arcsec/pixel and a total field of view in its imaging configuration of 11" x 11". Broad and narrower (Dl~1µm) band filters with the following central wavelengths are available: 7.9, 8.8, 9.8, 10.3, N-band (10.8), 11.7, 12.5, 18, 20.8µm. OSCIR has a KRS5 window.

In its spectroscopic configuration, OSCIR on Gemini has a slit length of 11 arcsec and the following slit widths: 0.227, 0.340, 0.454, 0.567, 0.681 and 0.794 arcsec. A low-resolution internal grating is available for the 10µm band and provides slit-limited spectral resolution with the 0.34 arcsec slit of l/Dl = 81.

The Gemini secondary mirror is capable of chopping, focus and tip-tilt image motion compensation. The standard mid-infrared technique of chopping (the secondary) and nodding (the telescope) is required to achieve accurate sky and telescope background cancellation.

OSCIR does not contain an on-instrument wavefront sensor and therefore fast tip-tilt guiding, which is mandatory for all observations with Gemini, requires guide stars to be acquired using the facility peripheral wavefront sensor(s).

Last update August 31, 2001; Phil Puxley