To: Raymond Blundell 
Cc: jzhao@cfa.harvard.edu, npatel@cfa.harvard.edu, cqi@cfa.harvard.edu, kyoung@cfa.harvard.edu,
     qzhang@cfa.harvard.edu, rwilson@cfa.harvard.edu
Subject: Re: SMA Data Reduction Software Meeting - followup issue

In the meeting today, it was mentioned that the receiver is not recorded
in the antenna-based Tsys file (tsys_read).   While this is true, strictly
speaking, it should not be a problem because the data is stored in a way
which allows the receiver to be determined unambiguously.   The file
stores the USB and LSB Tsys values for 48 chunks.   When we are in double
bandwidth mode, those 48 chunks are all for the single active receiver.
When we are in dual receiver mode, the lower 24 slots are filled with the
Tsys values for the low frequency receiver, and the upper 24 slots are
used for the Tsys values of the high frequency receiver.   When we are in
single receiver, single bandwidth mode, the Tsys file is layed out as it
would be in dual receiver mode, but the Tsys slots for the unused receiver
are filled with NaN values.   Which receiver (230 or 345) is the lower
receiver, and which is the higher receiver, can be determined from the
baselines file (bl_read).   So I don't think we need to change the format
of the Tsys file.

Taco