A Standard Filter Set for the 20 Micron Spectral Region
Session 26 -- Detectors and Telescopes
Display presentation, Tuesday, 31, 1994, 9:20-6:30

[26.12] A Standard Filter Set for the 20 Micron Spectral Region

D.Klebe, W.J.Williams (U of Denver), G.Orton (JPL/Caltech), B.Jones (UCSD)

Historically, broad-band photometry in the 17 to 28 micron spectral region has been limited to the use of the Q filter ($\lambda$=20 $\mu$m, $\Delta$$\lambda = 8 \mum). The advent of large format arrays with quantum efficiencies that peak in this portion of the mid infrared has prompted the need for more detailed wavelength coverage over this spectra region. Though this spectral region is dominated by water vapor absorption, there still remain several atmospheric windows of very good transmission, especially during dry sky conditions. In this paper we present transmission spectra inferred from sky emission observations taken with a high-resolution (R=200) grating spectrometer designed to operate from 17 to 28 microns. These transmission spectra clearly delineate atmospheric windows and demonstrate how these windows are affected by varying amounts of water. A set of seven filters has been selected to match the transmission features observed throughout this spectral region and are currently being manufactured. The central wavelengths and passbands for this filter set are: \\Q_{0} \hspace{.3in} \lambda =17.24 \mum, \Delta$$\lambda$ = .42 $\mu$m, \\$Q_{1}$ \hspace{.3in} $\lambda$ =17.93 $\mu$m, $\Delta$$\lambda = .43 \mum, \\Q_{2} \hspace{.3in} \lambda =18.67 \mum, \Delta$$\lambda$ = .47 $\mu$m, \\$Q_{3}$ \hspace{.3in} $\lambda$ =20.82 $\mu$m, $\Delta$$\lambda = 1.53 \mum, \\Q_{4} \hspace{.3in} \lambda =22.79 \mum, \Delta$$\lambda$ = 1.12 $\mu$m, \\$Q_{5}$ \hspace{.3in} $\lambda$ =24.48 $\mu$m, $\Delta$$\lambda = .64 \mum, \\Q_{6} \hspace{.3in} \lambda =25.67 \mum, \Delta$$\lambda$ = .30 $\mu$m.