Locked Segments in LIGO E7

Locked, Clean Segments and Playground Data

News about Playground data (April 15): After the playground lists below were posted, some bugs were discovered in the code that generated the clean segments for the interferometers. After a laborious and thorough process, Dave Chin has now generated new lists of "really clean" segments, found in his web page. (We should all thank his efforts in this!)
I have checked the new lists against our original triple-coincidence playground data (PlayL1H1H2.txt). We had 16 segments in our list. The file CorrectedPlayL1H1H2.txt has the original list, the new clean segments that have some intersection with the original ones, and the intersection between our original list and the new list. Here is a qualitative description of the changes:

For most segments (1,2,3,6,9,10,12,13,14,15,16) the only difference is that the segments should have ended 2 seconds earlier. (One of the interferometers, not always the same, was unlocked in those two last seconds, so those seconds should look pretty bad!).
Segment 4 (starting at 693793929) is now broken into two segments, due to some H1 filters being switched on and off in the middle. Notice that if only the L1-H2 coincidence is taken into account, this segment is OK as in the original (H1 is the interferometer that makes the last segment end two seconds earlier).
Segment 5 (starting at 693836545) and Segment 8 (starting at 693961593) should end two seconds earlier AND start 4 seconds later. This is also true if only L1-H2 coincidence is considered.
The times in segment 7 (starting at 693943838) include times for which there were missing frames in LLO due to the Y2K+2 problem. (See more details about missing frames in the RDS web page.). We could tell the interferometer was locked and the interval was clean, but we have no data! There were some efforts to recover this data, but I'm not sure what the status is.
L1 in Segment 11 (starting at 694147877) has a particularly noisier spectrum due to dewhitening filters not being switched, so although it is a valid coincident segment, it is not "clean" in the sense that the detector doesn't have the right parameters.

Since the consensus seems to be that L1-H2 coincidence is probably the only one that matters, I include here a list of L1-H2 coincident clean segments that have a non-zero intersection with the original playground list. Notice that these are in general (but not always) longer than the original playground segments.

Original playground lists

Using the conlog tool and database information at the sites, we can tell when the interferometer was being tweaked or filters were being switched on. We use this information to find a list of "clean" segments, when the interferometer was locked AND it wasn't "touched". Most of the "touches" that may happen are certain to trigger burst and inspiral searches, while the rest probably makes the data unusable (such as alignment or calibration procedures). Also, the interferometer does not have its typical noise spectrum until all the right filters have been switche don after the instrument locks. For all these reasons, data analysis should not be done on the "unclean" segments. The file L1comments.txt illustrates the concept, with a comment field for each segment, either "CLEAN" or something descriptive of what was happening. Some segments were broken into unclean portions leaving the clean portions as a separate segment. Dave Chin has followed this idea, and produced nice data, presented in a web page: http://tenaya.physics.lsa.umich.edu/~dwchin/LIGO/E7/LockSegments/. Using this information, I generated some "playground sets" that the bursts adn inspiral upper limits can use without biasing the future results of astrophysical searches on the whole E7 set. These are the steps I followed: I first found clean segments when L1 was locked, and both H1 and H2 were not locked; clean segments when H1 was locked, and both H2 and L1 were not locked, and clean segments when H2 was locked but L1 was not (without a condition on H1). I then took away from these segments the ones that were taken with L1 in "robust" mode, and the times near or coincident with Gamma Ray Bursts, as reported by Szabi Marka to us. At some of chosen times for L1, signals were injected. I did not exclude these times, but rather added a comment for the segment. So, here is the playground set.

The format used in each file is a list of initial GPS time, followed by duration in seconds. We have in these sets a total of 13.8 hrs in H1, 29.6hrs in H2, 27.6hrs in L1. A graphical summary of the chosen data, day by day, can be found in a PDF file: E7PlayTime.pdf.

[[Note! On Feb 1, we discovered D. Chin's lists of clean segments in each interferometer were missing some short locked segments (shorter than ~5min). Therefore, in some of the segments in the lists above, there is not a strict anti-coincidence: for example, in PlayH1noH2L1.txt, H1 or H2 are locked for few minutes at a time. We decided to stick with the same lists, instead of shortening them to strict anti-coincident times, since short segments will probably not be useful for coincidence analysis anyway.]]

We add to the "playground" a list of 16 clean segments in which all three interferometers were locked. The segments are between 15 and 20 minutes long, and they add up to 4.8 hours, or 10% of the 46 hours we have for triple-coincidence analysis.

PlayL1H1H2.txt

[[New (Feb 06 2002): I discovered one of the segments in the list above was a time when calibrations were being done. (I apologize for that, I thought the clean segments excluded those times). The segment in question starts at GPS 694147877 (Jan 4 2:51 UTC).]]

Finally, we have chosen a few segments of each list giving them "priority" for any analysis to be done. We suggest looking at these segments first, so we can collect information and compare results on the same segments even if people cannot analyze the whole playground.

PlayHereFirst.txt

Enjoy the playground!!

Clean segments with injected inspirals:

Peter Shawhan injected inspiral signals in the interferometer hardware, as mentioned in elogs and in his email. I looked for the clean segments in each interferometer around the time when the signals were injected:

Injections.txt

Summary table: how many hours of data?

E7 run for 18 days, or 432 hours. The numbers below follow from the lists of locked segments presented here, and the lists of clean segments generated by D. Chin, in here. They were updated after changes in Feb 1.

                all segments            segments >15min

L1 locked       284hrs (71%)            249hrs (62%)
L1 clean        265hrs (61%)            231hrs (53%)
L1 longest clean segment: 3:58

H1 locked        294hrs (72%)           231hrs (57%)
H1 clean         267hrs (62%)           206hrs (48%)  
H1 longest clean segment: 4:04

H2 loked         214hrs (53%)           157hrs (39%)
H2 clean         162hrs (38%)           125hrs (28%)
H2 longest clean segment: 7:24

all L1, H1, H2
locked            140hrs (35%)           72hrs (18%)
clean              93hrs (21%)           46hrs (11%) 
longest clean segment: 1:18

H2, L1
locked            160hrs (39%)            99hrs (24%)
clean             113hrs (26%)            70hrs (16%)
H2,L1 longest clean segment: 1:50

Plain Locked Segments

The files L1.txt, H1.txt and H2.txt have a list of locked segments longer than 5 minutes for each interferometer. These were generated by stitching together information from the metadata database on Segments, using Guild. The source information so obtained is in H1IfoLocked,H2IfoLocked, and L1IfoLocked. The code that generated the list of locked segments is a Matlab program, GuildSingleIfoStats.m. The Matlab program also produces summary statistical information, and statistical plots, found in FinalH1Figs.pdf, FinalH2Figs.pdf, FinalL1Figs.pdf. Similar information for segments when two or three interferometer were locked simultaneoulsy was generated with GuildTwoIfoStats.m and GuildThreeIfoStats.m. We also generated information on times when one interferometer was locked and the other two were not, or when one was locked and one other was not, using the scripts GuildThreeMinusTwoIfoStats.m and GuildTwoMinusOneIfoStats.m This is the complete list of segments:

The Matlab commands used can be found in the script RunAll.m, and the statistical information obtained (and posted in LLO elog) is found in the file FinalSummary.txt. WARNING!!!! The criterion used for defining locked segments is only a threshold crossing in the power stored in both arms. There is NO guarantee that settings were not changed during the locked segment. In fact, settings WERE changed in most, if not all, the segments at the beginning and/or end of the segment. The change in settings are almost guaranteed to trigger any burst or inpiral search.