What Each AOT Does
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 resolution 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.
The observer gives a set of "exposures"
that list minimum S/N to be achieved or time to be spent at
a set of up to ten wavelengths within the range.
The time per grating position satistfying all exposure
requirements is then determined and used.
Data is recorded from all 10 setectors while the range is being scanned.
The observer has a choice, in fractions of a resolution element, of the
spectral sampling interval.
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.
The observer has a choice, in fractions of a resolution element, of the
spectral sampling interval and also selects
the number of additional resolution elements
to scan on either side of the central resolution element.
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.
The observer has a choice, in fractions of a resolution element, of the
spectral sampling interval.
The observer gives a set of "exposures"
that list minimum S/N to be achieved or time to be spent at
a set of up to ten wavelengths within the range.
The time per grating position satistfying all exposure
requirements is then determined and used.
Note that the Fabry-Perot's low transmission
lends this mode of observing to only the brightest sources.
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.
The observer has a choice, in fractions of a resolution element, of the
spectral sampling interval and also selects
the number (three or more) of additional resolution elements
to scan on either side of the central resolution element.
Note that the Fabry-Perot's low transmission
lends this mode of observing to only the brightest lines.