[evlatests] how often do we observe in narrow bandwidths?

[Bryan Butler]

all,

so, based on the discussion we've been having recently, i decided to go 
through the archive and see just how often we observe in the various 
bandwidths.

i went through the actual visibility archive, from september 7, 2003, 
right up to the present.  for every record, i tabulated which bandwidth 
code each IF was in and how many antennas were present.  so what i 
counted up were antennas*IFs*time.  at the end, i divided by (4 * 27), 
for 4 IFs, 27 antennas.  so it's like the effective number of days 
observing at that bandwidth, if all 4 IFs and 27 antennas were observing.

i tabulated two totals, one for all observing, the other for "science" 
observing, which i determined as anything with a program ID starting 
with "A*N" (* is any letter, N is any number 0-9).

here's the resulting table:

BWcode   all observing        science observing
0        787.5  (62.4%)        433.3  (50.9%)
1        138.4  (11.0%)        122.7  (14.4%)
2         33.8   (2.7%)         18.2   (2.1%)
3         68.4   (5.4%)         59.5   (7.0%)
4        101.7   (8.1%)         91.5  (10.7%)
5         99.0   (7.8%)         95.2  (11.2%)
6         29.3   (2.3%)         28.0   (3.3%)
7          0.1   (0.0%)          0.1   (0.0%)
8          0.8   (0.1%)          0.5   (0.1%)
9          4.0   (0.3%)          3.2   (0.4%)


one might think that this had changed significantly since the large 
projects initiated this summer.  one would be mistaken (well, depending 
on your definition of significant).  if i tabulate things from July 1, 
2007, to the present, the table is:

BWcode   all observing        science observing
0         90.6  (58.2%)         41.5  (42.3%)
1         30.9  (19.9%)         27.4  (27.9%)
2          2.7   (1.7%)          1.3   (1.3%)
3          7.9   (5.1%)          6.6   (6.7%)
4          2.7   (1.7%)          1.7   (1.7%)
5         11.6   (7.5%)         11.1  (11.3%)
6          8.8   (5.6%)          8.4   (8.6%)
7          0.0   (0.0%)          0.0   (0.0%)
8          0.0   (0.0%)          0.0   (0.0%)
9          0.3   (0.2%)          0.2   (0.2%)

there is an increase at bandwidth code 6, by a factor of 2.5 or so.  but 
5, 7, 8, and 9 are basically unchanged.

so, the question is, do we want to go to much effort, including a 
potential many-months-long delay in EVLA, to make a change to fix 
something that might affect something like 10%-20% of observing in the 
transition system (i'm counting modes 5 and above here)?  i leave it to 
those more erudite than i to decide.

	-bryan