Memo Review Reply

Memo: 372 - An Amplitude Calibration Strategy for ALMA
      Moreno & Guilloteau, 2002May10

Reviewer: Larry D'Addario

Date Received: 2002Aug22

Reply from: Mark Gurwell

Date Received: 2002Aug22


Reply:

I know I said I couldn't review the amplitude calibration memo, but
I could not let Larry's email on amplitude calibration pass through
without a quick comment on the need for sideband ratio calculation;
he claims that the sideband ratio is unimportant for continuum 
observations, and that 'sideband suppression' within the correlator
makes it unimportant for line work.   

These comments may be true at low frequencies where the atmospheric
opacity is the same in each sideband, but they are definitely not
true in the case where the opacity is different.  Only with a 
knowledge of the SBR can one accurately use the measured system
temperature (which is inherently a DSB operation) to get the single
sideband system temperature which is the first order correction
to amplitude.  This situation becomes more and more important at
the higher frequencies, and especially in band 8 where the window
is narrow and chopped by many water lines.