Last modified by Felipe Mac-Auliffe, April 30th 2002
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Twice a month a spectral purity test is done using both the high and low resolution
AOSs. The test is done by inserting a test signal at a fixed frequency before
the first mixer and detecting it with the spectrometers. In this way it is checked
that the frequency scale is correct (the testsignal should fall in the center
channel of the spectrometer) and that no unforeseen line broadening occurs due
to the LO system or the spectrometers. The center channel for each AOS, which
defines the central velocity set by the observer, may jump due to power surges,
temperature variation or vibrations in the AOS room. It is important to check
for line broadening effects in order to to ensure that the line widths inherit
to the system are negligible when observing narrow emission lines or analyzing
emission line shapes. Thus, these tests also allow an estimate of the performance
limit of the system for observing narrow lines. In addition a continuous logging
routine monitors the position of the center channel for each AOS.The line width
/ central channel plots are presented in the following table for all the SEST
available receivers & AOS's:
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Last modified by Felipe Mac-Auliffe, April 30th 2002 |
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