Timing Diagnostics of the
Physical Environment Monitoring System During S5
The timimg-monitoring channels at LHO and LLO detectors, such as
H1:DMT-TIME_EX, L1:DMT-TIME_PEM etc., measure the difference between
the GPS time "tick" and the time stamp of the Physical Environmental
Monitoring system (PEM) data in the frames. In the ideal case this
difference should be zero, however, in practice deviations in the order
of 10s of microseconds are common. This is due to the LIGO
software/hardware implementation for these systems and up to 64
microsecond deviation was deemed acceptable for these slow channels.
The statistical error on the generic timing measurement is in the order
of tens or hundreds of nanoseconds, while the systematics are
estimated to be in the order of microseconds. Therefore, if neccessary,
the timestamp of the data can be corrected and the resulting timestamp
trusted at the order of microseconds using the data presented here.
The minute trend of the DMT reduced data (TimeMon) was used to make the
tables below, covering the S5 science mode segments with duration of at
least 600 seconds. These figures present the time-series, histogram,
and normfit [see Matlab documentation] plots for H1, H2, and L1 PEM
channels in all LVAs. Beyond graphical output, detailed data is also
provided in tabular and LaTex formats. The summary data is available
per science mode segment, per day, per week and per month basis. Mostly
due to reboots, values of measured time delays fluctuate cosiderably
beyond the statistical error, therefore the long duration plots show
complex time dependent behaviour. While it is educational, it is
imperative that for data analysis purposes only the science segment
based data is used.
The directory structure and contents:
tables/Mean and STD measurements are reported in microseconds.
scripts/ Contains
the matlab functions that are used to produced the figures, tables,
data files etc. The *.list files contain complete S5 science segments
information.
segment_timing/
Contains files with information about PEM timing accuracy at various
LIGO stations during each science segment over the duration of whole of
S5. Both MAT and ASCII format files are provided. Mean and STD values
are reported in seconds and not microseconds in these tables. For data
that is still to be processed, a NaN is displayed for now as the Mean
and Std.
figures/ Contains
the monthly, weekly, daily, and science segment plots for various
TimeMon trend channels in eps and png format for the
whole duration of S5 as well as relevant tex files that can be useful
for producing report using these figures. For including the png figures
in a report, please use the pdflatex package instead of the
conventional latex package and the png_Time_mon.tex file instead of the
Time_mon.tex file. Please note that each eps file can be up to multiple
megabytes in size whereas each PNG file is roughly below 50KB.
Rubab Khan, GECo,
Last Updated: December 07, 2007.