From Fri Feb 15 14:56:33 2002
Date: Fri, 15 Feb 2002 12:39:22 -0600 (CST)
From: Giles Novak 
To: Tom Renbarger ,
     David T. Chuss ,
     Jeffery Peterson ,
     Jessie L. Dotson 
Subject: signals really are 4 x bigger!

Hi Tom, Dave, Jeff...

In Tom's thesis (and on web page and in recent proposal) it says that we
expect 4x bigger optical efficiency based on analysis of load curves and
known transmission of some optical elements.

In early Dec., I mapped RCW 57 and got 30 "map units".  In March 2000,
Greg mapped it and got 21 units, according to Dave's analysis on web page
"plan for setup..."  Taking into account the difference in tau (1.2 winter
vs. 1.65 summer) and responsivity (a factor of 1.6 worse after upgrade,
for summer Pole temps near 250 K, see web page), we get an improvement of
a factor of 3.85 times.  Given the uncertainties we should say we are 3-5
times more optically efficient.  This corroborates what we thought we had
done to the optical efficiency!

Because we were detector noise limited in 2000, we get almost the full
factor of 3-5 increase in signal-to-noise!  (The theoretical prediction
based on estimates of transmission, detector NEP, winter-time
responsivity, etc., is a factor of 2.7 increase.)  Every day of observing
in winter 2002 will be like a full week (2.7 squared) of winter 2000

- Giles