OSCIR Sensitivity

caution Important caveat: these are preliminary values from tehfirst OSCIR engineering run. They make some unverified assumptions about the telescope performance.

All sensitivities are 5 sigma 1 hr of chopped integration (i.e. 30 min on source). No overheads are included; for example, with a 70% chop-nod duty cycle this integration would have an elapsed time of about 85 minutes. See the performance and use section for more details of overheads including those for target acquisition. Note that the sensitivities depend strongly on the atmospeheric water vapour content at the time of the observations.

Mode Point Source
(mJy)		 Extended Source
(mJy / pixel)		 Notes
Imaging
broad-band N (10.8µm) 0.6 0.14 (a, b)
narrow-band 8.8µm (best) 0.7 0.21 (a, c)
narrow-band 12.8µm (worst) 1.2 0.24  
broad-band Q (18µm) 10 1.5 (d)
Spectroscopy
low res. (10.8µm) 10 - (e)

Notes to table:
(a) assumes combined system emissivity of telescope, warm optics and atmosphere of 8%, expected median delivered image quality (50% EED) for point source of about 0.4 arcsec FWHM and software aperture of diameter lambda/D.
(b) broad N-band filter FWHM = 5.3µm
(c) narrow-band filter FWHM = 1.0µm; 8.8 is the most sensitivite and 12.8 is the least sensitive
(d) IHW18 filter FWHM = 1.7µm
(e) Spectroscopic sensitivities estimated by scaling from imaging benchmark as sqrt(relative resolving power / relative throughput); assumes 0.34 arcsec slit

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Last update August 31, 2000; Phil Puxley