From: <adeller_at_email.protected>
Date: Fri, 18 Mar 2005 10:45:44 +1100 (EST)

Hi Jim,

On Fri, 18 Mar 2005, Jim Lovell wrote:

>Hi Adam,
>
>Very nice! I have a few comments in addition to Tasso's:
>
>1. Could you change Tid43 and Tid45 to Tid_70m and Tid_34m please? It's
>a bit more descriptive as not everyone knows which DSS number
>corresponds to which antenna.
>

Good point - done

>2. At 2.3 GHz what Tsys are you assuming for the 70m? There are two LNAs
>and one has a significantly better performance than the other (but only
>30 MHz bandwidth). See
>http://www.atnf.csiro.au/observers/docs/tid_obs_guide/tid_obs_guide.html#Receivers. For single polarisation and bandwidths of 32 MHz or less then the hempt can be used but for dual polarisation, both must be used. If it is dual pol then we generally switch the maser through a diplexer which raises it's Tsys a bit and makes it a better match to the hempt. So to summarise (!):
>single pol, bandwidth <= 32MHz : Tsys = 16K
>dual pol : Tsys = ~25 K
>bandwidth > 32 MHz (must be single pol) : Tsys = 25 K
>This is all a bit beyond the scope of your tool, so see the next point:
>

At the moment I have Tsys 16K, which I took straight off the
http://www.atnf.csiro.au/vlbi/documentation/ page.

>3. How about a drop-down menu with all the standard S modes? (see
>http://www.atnf.csiro.au/vlbi/observing/lba_s2_configs.html). This would
>set the bandwidth and observing frequency accordingly and could also
>select the appropriate Tsys for the 70m at 2.3 GHz. There could be an
>"other" option which would let people set their own frequency and
>bandwidth.
>

Okay... That might be a little bit of extra effort since it wasn't really
designed with that in mind. What does everyone think? If everyone thinks
it would be really handy then I'll put it on my to-do list and make it
happen at some stage over the next week or so. So for the time being I'll
leave the Tid 2.3 Tsys at 16K and put a note on the bottom of the page
explaining the reduced sensitivity at >32MHz and/or double pol.

>4. Is the baseline sensitivity quoted for the "Calibrator time/scan"
>time? If so, that should be made clear.

Yes, I've added an extra line in the table to make that clear

>
>5. Any reason why only a single ATCA antenna is available at 22 GHz? In
>compact configs it may be possible to phase up some antennas.
>

I interpolated that from the vlbi/doc page, which had 1 antenna and 6
antennas (with 6 antennas not available for 12 or 22 GHz). If it is
possible to phase 3 antennas for 22 GHz I'll change the definition to make
that available.

>6. Is it possible to show an estimate of the synthesised beam major and
>minor axes plus position angle?
>

That is something I'm looking at but it seems like it might be a bit
difficult. I'm hunting around for a good elliptical Gaussian fitting
method in Java - if anyone knows of one, please let me know!!

Thanks for the feedback,

Adam
Received on 2005-03-18 10:46:09