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LBA issues

From: <Philip.Edwards_at_email.protected>
Date: Mon, 2 Mar 2009 15:50:15 +1100

Hi LBAers,

We've become aware of issues affecting Mopra and the ATCA during the last session.

The pointing parameters file for Mopra somehow got clobbered a few weeks ago.
The HOPS team, doing single-dish 12mm Mopra observing, noticed the effects of this on their data mid-way through last week, but believed they had data ruling out a likely pointing problem, which had led us to pursue this as a MOPS-only problem. Chris had done a 22GHz ATCA-Mopra fringe check at short notice last week which did yield fringes, indicating that the pointing wasn't in error by much more than the 2 arcmin full-width at half-power - at least in that part of the sky. As the LBA week only had observations at 8.4GHz and lower, and as all fringe-checks were successful, the impact on the LBA observations is not likely to be large. We will be able to determine the expected pointing error across the sky and so will be in a better position to quantify this in the next couple of days.

At the ATCA, we had noticed that one IF (freq 2, LCP) displayed somewhat odd phase and amplitude behaviour, with quasi-sinusoidal variations across the band.
Suspecting a DAS module, we swapped modules over today but found the problem stayed fixed.
After the LBA session ended, we found a re-boot of the tied array box eliminated the problem.
This was the last LBA session with that tied array box - a unit which has, apparently, had "issues" in the past -- as we will have a new one for the CABB era.

Regards,
Phil
Received on 2009-03-02 15:50:50