[mmaimcal] amp cal using 183 GHz radiometer

[Min Yun]

In case anyone did not notice, Stephane's statement that 183 GHz
radiometer measurments can be used to achieve the amplitude
calibration (and that cooled radiometer is needed) is stated in
the context of using 183 GHz radiometer to track atmospheric
fluctuations in page 6 of Robert Lucas memo (No. 300).  
The problem of determining atmosheric term in the amplitude
gain is largely quivalent as tracking the atmospheric fluctuations
as discussed in this memo,
and all of the same problems that plague the use of the radiometer
to track atmospheric fluctuation also apply to the amp cal problem
as well -- actually worse since amp cal requires absolute 
measurements rather than relative.  Given the problems
with the required sensitivity, beam offsets, atmospheric
modeling accuracy, etc., achieving the "1% amplitude
calibration accuracy" using the radiometer seems very difficult do.  
We really should ask Stephane to work out the details better and 
demonstrate this will work if he wants this idea to be taken 
seriously by the project.




					-- Min