TOG report for Westerbork, March 2006

Sessions

Since the last TOG meeting Westerbork took part in sessions 2005-3 and 2006-1

92cm polarizations were swapped in 2005-3
Westerbork had fileserver problems which caused all systems to freeze in 2005-3
In session 2005-3 1Gbps recordings were unreliable. Suspicion fell on crosstalk between the video output cable and flatcable inputs to the Mark5A

VLBI rack

There were recurring minor problems with the gain stability of BBC01.

Recorders

Mark4

The Mark4 was used in 2005-3, but caused some formatter glitches when recabling from disk/tape or back. The vacuum motor was replaced in October. It was not used at all in 2006-1, and we plan to remove it as soon as possible to make room for the digital tied-array hardware

Mark5A

Shortly before session 2005-3 Westerbork had problems with erasing and conditioning the disk packs, so we borrowed a Mark5A from JIVE. We returned this before session 2006-1 and found that our unit had unusual symptoms which were traced to problems with the power supply. We replaced this shortly before the session with another standard 550W power supply (which was on the shelf in Dwingeloo as a spare for a server). The PSU that came out was tested and under load the 5V lines dropped voltage rapidly if the load was even 0.8A (for a 40A rated unit). We also re-routed the input flatcables and the video cable to avoid crosstalk (the alleged cause of the 1Gpbs problems).

Field System

The FS computer that arrived in 2005 was used without problems in both sessions. The initial problems were found to be caused by the software having been setup for another motherboard, and not having been modified when the underlying hardware was changed. The old FS computer is still available as a spare with a recent FS version.

Kuper implemented scripts that interact between the TMS (local control software) and FS. These can

Calculate the sky frequency from BBCs local IFs and receiver setting ( for operators to check)
Report when telescopes are on/off source for logging when the tied array data is valid

Foley also implemented a python script that can control the frequency of 1 telescope (RT7) to use during single-dish observations. It was used for 5cm (methanol/OH) observing, but in principle it can be used for any frequency

Other systems

The telescope control was moved to another computer which has no crossmount to the field system, so the antcn program to point a single dish were modified

Plans

We plan to replace the old meteo station with a newer one to get more accurate information ( the old one sometimes gave spurious data, and so could not be relied on to automate parking the telescopes in a storm)
We plan to use another GPS clock as the 1pps referenc
The digital tied array hardware exists (mostly) and is planned to be operational from summer 2006 - so we will need to test it