[asac] Message from Neal

[Min Yun]

Thanks for clearing that up, Geoff.  This is consistent with what
I have learned from Al Wootten today, but I felt we needed an official
explanation from the receiver group.  As I said in my e-mail, the
particular example of measuring dust SED is not severely impacted
by this limitation, but it does bother me that a project that needs
only a few minutes of on-source integration would require an hour
or more of obsering time simply because of this limitation.  One
cannot always assume that this type of study will be done for a
cluster of sources.  Study of a GRB, for example.  Since
there are some foreseeable scientific implications tied to this
number, it would be good to scrutinize it a bit and urge the
receiver group to find ways to minimize the impact on observations.



					-- Min
					
					
> 
> Hi All,
> 
>   I believe Ewine's earlier mail summarized the 15 minute issue with the
> receivers and it is the following.  Three receivers (the WVR plus two
> astronomy receivers) can be on at any one time. The 15 minutesis the time
> needed to get a receiver up and going from a COLD start. It takes a bit
> for the amplifiers to warm up and stabilize, etc. I suspect things like LO
> switching and so forth are very much faster.  So, the question is, if you
> have two receivers that are on, and you need to switch to a third, how
> much will that limit the available science.  If this is a serious issue,
> we should let the receiver group know very soon that we are concerned with
> this length of time.
>   I would note to Min that if there are a few sources that are close
> enough that the switching (i.e. moving and pointing) time is short, you
> can do a few sources with the active receiver while the new tuning warms
> up, so I find it hard to believe this will be a very serious limitation.
> 
>   Geoff
>