[mmaimcal] [bbutler at cv3.cv.nrao.edu: Re: [alma-sw-ssr] Pipeline Requirements new version]

[Bryan Butler]

al and i had forgotten to include the appropriate lists on these
replies...

	-bryan


On 2001.08.30 10:22 Bryan Butler wrote:

al is right here (i was thinking of the situation for only 1 antenna).
but sub-arraying is essentially the 'paired antennas' (or 'clustered
antennas') calibration concept, which is terribly inefficient for calibration.

	-bryan


On 2001.08.30 10:19 Al Wootten wrote:
> Bryan Butler writes:
>  > On 2001.08.30 09:34 Mark Holdaway wrote:
>  > > 
>  > > Mel wrote:
>  > >
>  > > > 2. At high frequencies, a suitable monitoring source
>  > > > may be found in the offset beam corresponding
>  > > > to a low frequency band. These
>  > > > offset beams move w.r.t. the target source, so the
>  > > > monitoring source will change with time, but one
>  > > > is only interested the phase, not the source.
>  > > > The simultaneous observation of the target at
>  > > > high frequency and a monitoring source in an offset beam
>  > > > at low frequency  requires  a few things, like
>  > > > 2 active receivers, sharing bandwidth and correlator,
>  > > > but has the advantage of a continuous phase calibration
>  > > > on a nearby source.
>  > > 
>  > > I think dual frequency observations have been ruled out by the systems
>  > > group.
>  > > 
>  > 
>  > i agree with mark here - simultaneous dual-frequency operation has
>  > been completely ruled out (if you don't count the WVR).  i'm pretty
>  > sure we are beyond the point at which this decision can be changed.
>  > the current design is that there is one 'hot' receiver - i.e., the
>  > one currently being used; there is one 'warm' receiver, which can
>  > be switched to on short timescales (1 sec or so, i think is the
>  > spec) - i.e., the low frequency Rx for fast switching calibration;
>  > and one which is 'ready to be warmed up' - i.e., the next observing
>  > frequency (it takes 10 or 15 secs for this to be ready, IIRC).
>  > 
>  > note that we are seriously considering this kind of a calibration
>  > scheme for the EVLA, where all of the receivers are 'on' all of the
>  > time.  there are some difficulties with transferring the phase, but
>  > it certainly looks promising.
> The only way one can effect simultaneous dual-frequency operation is through
> the use of sub-arrays.  One is using different antennas in that case, but
> depending on the configuration one may be observing a similar patch of
> atmosphere.
> 
> Al
> 
> 
> 
> 
>