Q. Which AOT (1,2,3,4) does what?

A. LWS01
   -----

   This Grating Mode AOT covers a wavelength range specified by the
   observer, between 43.0 and 196.7 um. The minimum range that can be
   covered is 1.25 um for wavelength below 90.5 and 2.5 um for 
   wavelengths above. The spectral element size is 0.29 um below 90.5 un 
   and 0.6 um above 90.5 um. This translates to (2000 km/s - 950 km/s) 
   from 43.0 to 90.5 um, and the same range again from 90.5 to 197 um. 

   LWS02 Line Mode
   ---------------
   
   This Grating Mode AOT produces medium resolution spectra at one to ten
   spectral line wavelengths specified by the observer. Data is recorded
   from all 10 setectors while the lines are being scanned. 

   LWS02 Photometry Mode
   ---------------------
   
   In the Narrow-Band Photometry mode of this AOT (used by setting the 
   scan width to zero) an under-sampled medium resolution spectrum over
   the full wavelength range of the LWS (43.-196.7) is produced: ten
   photometric points - one in each detector channel - at a resolution of
   0.29 in the five channels at wavelengths less than 90.5 um and 0.6 um 
   in the 5 channel above 90.5 um. In this usage of LWS02, the grating is
   not scanned, but rather remains in a fixed position. 

   LWS03
   -----
   
   This AOT results in a high-resolution spectrum covering a wavelength 
   range, specified by the observer, up to the full range of the LWS
   (43.0-196.7) using the Fabry-Perot Interferometer. Data will be
   recorded only from the detector(s) in the range, with a single
   detector sampled as the range is scanned. 
   
   LWS04
   -----
   
   This AOT produces high resolution (lambda/delta lambda = 8000-9800, or
   31-38 km/s; see the LWS Manual for details) spectra for one to ten
   lines. Data will be recorded only from the detector at the line
   wavelength, with the single detector being sampled as the line is
   scanned. 
   
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Q. What do you mean, I get 9 detectors free?!

A. The LWS is a multiplexing instrument. A full scan of the grating
mechanism would send 50 to 70um radiation to detector SW3 while, AT THE
SAME TIME, detector LW5 receives the radiation from 160 to 200um. This
is because the 10 LWS detectors are placed one after the other; the
output angle of the grating will be different for all detectors which,
therefore, will receive each a different wavelength. 

==================

Q. When do the detectors saturate?

A. For the detectors in grating mode, indicative figures for the saturation limits are as follows: 

SW1     122000 Jy         47 microns
SW2      55700 "          57    "
SW3      54000 "          67    "
SW4      73600 "          77    "
SW5      10200 "          86    "
LW1      29600 "         105    "
LW2       8100 "         125    "
LW3       3400 "         144    "
LW4       7900 "         165    "
LW5      10800 "         180    "

FP limits are about a factor of 100 higher. Observers dealing with solar
system objects will definitely have problems in most of the wavelengths;
they should contact their ISO Support Centers for a proper data
reduction. Other observers will have most likely to deal with saturation
problems for detectors LW2, LW3 and LW4 at most; a tools is available to
correct for these problems and observers are advised to contact their
ISO Support Centers.

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