The SWS instrument consists of two nearly independent grating spectrometers,
together covering the wavelength range 2.38-45.2 
m with an overall
spectral resolution of 
1,000-2,000 (i.e., 
300-150
km s
). By inserting Fabry-Pérot (F-P) filters, one for the range
15-26 m (with capability down to 11.4 m at reduced
resolution) and the other for the region
26-35 m (with capability to 44.5 m at reduced sensitivity), the
resolution can be increased to 30,000 (i.e., 10
km s) .
N.B.: Click here for better view
Figure: Lay-out of SWS
Fig. 
gives an impression of the lay-out of the SWS,
an optical block diagram is shown in
Fig. , and an optical schematic is shown in
Fig. .
The IR radiation is reflected into the SWS by the ISO pyramidal mirror.
The SWS has three entrance apertures , each with its
own dichroic beamsplitter feeding the Short Wavelength section and the Long
Wavelength section. The appropriate entrance aperture will be selected
by specific pointing of the ISO satellite. A four-position selection
mechanism permits opening of any one of these apertures or blocking of
all three.
Tab.
shows how the SWS grating wavelength region is subdivided in
16 wavelength bands , instrumentally dictated
by aperture , spectral order, filter material and
detector type.
Table: Definition of the wavelength ranges of the SWS AOT bands
