From jzweizig@ligo.caltech.edu Fri Feb 8 13:22:32 2008 Date: Fri, 8 Feb 2008 10:18:49 -0800 (PST) From: John Zweizig To: Gabriela Gonzalez Cc: Glitch Working Group Subject: Re: BS oplev problem and equinox candidate Hi Gaby, I have looked at various sigma distributions reconstructed from BS_OPTLEV minute trends. The POUT trends show a noticeable increase in scatter at ~1430UTC on August 23, 2007 which then reverts to "normal" at ~2300UTC Sep 21, 2007. Looking at Optlev gain channels in conlog shows: Date 8/01 0000 8/23 1436 9/21 2240 BS_OLPIT_GAIN 121.7 134.5 106.4 BS_OLYAW_GAIN 307.7 296.5 245.8 So, assuming that the gain changes were responsible for the oscillations, the time period would have been 8/23 to 9/21. However, looking at the trends, I can see the oscillations you noted on 9/21, but not much that is comparable in the rest of the period. I also ran an automatic scan on the trends to tag segments with large sigma optlev_pout sigmas. The resulting list is attached to this email. The majority of such segment are probably indiuuced by sesmic activity rather than the oscillations seen on 9/21, although some seem to be due to oscilaations ans are clearly correlated with dips in the L1 inspiral range (e.g. on 9/13 and 9/21). Best regards, John On Mon, 4 Feb 2008, Gabriela Gonzalez wrote: > Hello, > > following up on the comments I made today in the glitch call, I wanted to > clarify the significance of the BS optical lever problem for the equinox > candidate. My observations arise from following the large standard > deviation of SenseMon in the segment L1-6313, ranked #3 in worse std for > all of S5, as shown in the list here: > > http://www.phys.lsu.edu/faculty/gonzalez/S5/L1BadSegs_AllS5/ > > (See also segment ranked #38). According to the elog on Friday Sep 21, > the "problem" that had been observed for at least a couple of days was > diagnosed and fixed by Brian and Valera: > > "We found that the BS oplev servo was gain peaking at 3.6 Hz in the low > noise. > The reason for that was the digital compensation of the dewhitening gain. > It is off by ~2 dB with dewhitening on. We set the BS oplev pitch and yaw > ugfs > in run state with dewhitening on." > > According to the elog's time and the operator's entry, the fix was done > between segments L1-6323 and L1-6324, so L1-6324 and later ones should not > be affected. > The equinox candidate, on Sep 22 3:05 UTC, happens during L1-6325, and > thus cannot have been caused by the optical lever problem. > > The segments L1-6312 to L1-6315 are very obviously affected; the ones that > follow (L1-6315-6318) do not show obvious problems in SenseMon but there > maybe problems in the data quality, the problem appears again very badly > in L1-6323. I don't know when the problem started, the elog on Sep 08 > mentions similar oscillations, so it may have been there for some time. > > Although the problem does not affect the segment with the equinox > candidate, it may affect estimates of false alarm that use times near the > candidate, if they include the noisy segments. > > The sequence I reconstruct is then: > > Segments most of which show a problem in range due to the BS oscillations: > L1-6312 4491 s 874369184- 874373675 2007 09/21 00:19:30 - 09/21 > 01:34:21 utc > L1-6313 5115 s 874374723- 874379838 2007 09/21 01:51:49 - 09/21 > 03:17:04 utc > L1-6314 2745 s 874381600- 874384345 2007 09/21 03:46:26 - 09/21 > 04:32:11 utc > L1-6315 9760 s 874385837- 874395597 2007 09/21 04:57:03 - 09/21 > 07:39:43 utc > L1-6316 3526 s 874397966- 874401492 2007 09/21 08:19:12 - 09/21 > 09:17:58 utc > L1-6317 19288 s 874402396- 874421684 2007 09/21 09:33:02 - 09/21 > 14:54:30 utc > L1-6318 345 s 874421938- 874422283 2007 09/21 14:58:44 - 09/21 > 15:04:29 utc > L1-6319 3611 s 874429308- 874432919 2007 09/21 17:01:34 - 09/21 > 18:01:45 utc > L1-6322 2025 s 874434243- 874436268 2007 09/21 18:23:49 - 09/21 > 18:57:34 utc > L1-6323 6618 s 874436696- 874443314 2007 09/21 19:04:42 - 09/21 > 20:55:00 utc > > Segment that follows the fix, which should not have problems due to the BS > oplev servo: > L1-6324 2007 s 874450664- 874452671 2007 09/21 22:57:30 - 09/21 > 23:30:57 utc > > Segment that contains the equinox candidate: > L1-6325 35320 s 874452908- 874488228 2007 09/21 23:34:54 - 09/22 > 09:23:34 utc > > I hope this is useful! > > Gaby. > > ------------------------------------------------------------ > Gabriela Gonzalez > Associate Professor > > Department of Physics and Astronomy > Louisiana State University > 202 Nicholson Hall > Tower Drive > Baton Rouge,LA 70803 > > Phone: (225) 578 0468 > Email: gonzalez@lsu.edu > http://www.phys.lsu.edu/faculty/gonzalez/ > > > > [ Part 2, "" Text/PLAIN (Name: "L-bs_pout_science.txt") 483 ] [ lines. ] [ Unable to print this part. ]