Summary of Sam Ragland's Run: 16-25 Nov. 2002

Hi All,

Over all, it was a successful run - half engineering and half science.

science measurements were made with the A35/B15/C0 array configuration during first five nights.

Telescope C was moved to C15 station on Nov. 22nd. Yesterday, I recorded the first closure phase measurements with the C15 station. The optimization of this unexplored station took more than a day. I also lost about one and half nights in looking for fringes with a wrong station parameters for C15.

Long delays gave some trouble. In my opinion there are two problems associated with the long delay.

The '+limit' of LD1 failed on the evening of Nov. 21st. I spent the whole night in understanding the problem without sufficient documentation on trouble shooting. I managed to disable the '+limit' (the OT was not complaining about this limit any more). However, the long delays were still not working, but with a different status flag now. I believe, the reason being a second problem associated with the LD server. Next morning, it worked when Marc disabled the '+limit' of LD1. But, on the same evening I had the problem again.

Occasionally, LD server thinks that the LDs are at home (that is what the flags say) when the LDs are not at home (as Pete mentioned earlier in one of his e-mails). This problem occurred to me a few times during this run. The start up sequence Marc listed in his e-mail seems to solve this problem.

The bottom line is:
(1) Always start the server program (./srv2) *before* running the 'vxworks_start' script.
(2) If you are required to reset the 'vxworks', kill the server program as well and restart it.

Surprisingly, this wasn't required in the past. We used to run the server program for weeks at a time without reloading it, while frequently rebooting the 'vxworks'.

One night, I had a polarization problem with the D2 fiber. Essentially, both the polarization components were reaching PICNIC. This problem disappeared when I was reconfirming the alignment of the polarization axis of the fiber. I think, tension in the D2 fiber caused this problem. Hopefully, we won't have similar problem with the new beam combiner which JP brought to IOTA yesterday.

The sky was clear all but the last night. The seeing was excellent on three nights. Unfortunately, I lost two of those good nights - one due to long delay problem and the other in optimizing the C15 beam. The seeing was very bad on two nights (3-5" seeing). The fringe tracker finds it too hard to lock the fringes under worst seeing, especially when scintillation noise is dominant in the data.

Have a wonderful Thanksgiving holiday.