From: <stingay_at_email.protected>
Date: Wed, 31 Aug 2005 14:55:29 +1000 (EST)

Jim,

>I'm a bit surprised that the non-detection from the 6m to Australia
>is due to sensitivity. Even in 1 second, a 5 Jy source should be
>detectable from a big Australian antenna to the 6m. All else being
>equal, the sensitivity of the 14m-ATCA baseline should be better than
>the 6m-ATCA baseline by the ratio of the product of the antenna
>diameters. So if 1-sigma on the 14m-ATCA baseline is 0.35 Jy, 1-sigma
>on the 6m-ATCA baseline should be 0.35 * (14/6) = 0.8 Jy. So 0537-441
>should be a 6 sigma detection to NZ in 1 second.

Yes, this matches my rough calculation of what we should have expected...

....If everything was working ok with the equipment, which I am not sure
it was. Pointing is a possible worry too, and timestamping of the data
was an even bigger worry at the time, as was the maser etc etc. We found
and eliminated a number of noise sources in the 6m environment that
substantially raised the Tsys. Also, we really have no idea how well the
feed sat at the focus of the 6m and how the surface (and surrounding
ground!) was illuminated by the feed. The sensitivity may well have been
compromised by a raised Tsys.

In short there are a number of unknowns with the 6m, which was exactly the
reason we did tests in a controlled environment in Hobart.

We now have a VLBI result and better confidence if we do a further test
with the 6m.

Cheers, Steven
Received on 2005-08-31 14:55:53