cal jumps aug05
The Tsys for sbw jumped from 34K to 24K around 18aug05.
This was the same time that the refrigerator was being worked on.
On 18aug05 the receiver log says that the cal cables were replaced. The
plots show the
sbw system performace during 2005 (ps) (.pdf):
It looks like the cal value injected in the sbw dewar has changed around
the 18th of august05. We probably need to remeasure the cal values.
fig1 Top: Gain versus date for 2005. The black * are before 18aug05,
the red * are after 18aug05.
fig1 2nd: Gain (K/Jy) versus za. Black is before the cable change red is
after. The gain decreased by about 30 %
fig1 3rd: Tsys (K) versus za. The Tsys increased by about 30%
fig1 4th: sefd (Jy) versus za. The sefd remained constant before and after
the change. The sefd does not depend on the cal values
fig2: This is the daily Tsys measurements versus date (using the high cal).
Black is polA (diode 1) and red is polB (diode 2). Both polarizations jumped
by about the same amount. If it was a cable problem, then the same thing
happened to each cable. During the 18th, 19th of aug05 the dewar warming
up and cooling down, so the tsys values were changing on these days.