LSC Detector Characterization Working Group
Subgroup on Transient Analysis
Leader: Fred Raab
In searching for coalescing compact binaries and for other rapidly varying
sources, it is critical to understand transient noise in the interferometers.
This subgroup is devoted to detecting and classifying transients arising
directly from the instrument or its environment.
Examples of transient types to be identified:
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Impulses / "wee dwangies" (e.g., dropped hammer, wire relaxation, BNC connector
slippage)
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Ringdown of violin modes
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Servo instability
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Excitation of out-of-band resonance
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Onset of analog or digital saturation
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ADC / DAQ malfunction (e.g., lost data, sticky bit)
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Earthquake / lightning / wind gust / cosmic shower
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Dust particle falling through the beam
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Non-stationary laser frequency and intensity noise
Examples of transient signatures and detection methods:
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Discontinuities, missing data
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Stuck bits, duplicated data
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Sudden increase in total or band-limited rms (IFO or environmental channel)
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Large amplitude excursion
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Non-random time-frequency behavior (waterfall/carpet plots, wavelet analysis)
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Matched filters for automated transient classification
The detection of an identifiable instrumental transient should provoke
a "trigger", that is, the writing of a record to the meta-database describing
succinctly the time and nature of the transient. In addition, if warranted,
an alarm should be sent to the interferometer control room to notify the
operator to take action. The basic infrastructure
for creating triggers and alarms is now under development within the
LIGO Lab.
What remains open, however, are the definition and implementation
of those triggers & alarms. These are natural tasks for this subgroup
to assist in and will involve coordination with both the Global
Diagnostics Systems (GDS) and LIGO
Data Analysis System (LDAS) groups.
General Plan
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Set priorities and find volunteers
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Define and implement simple triggers & alarms, including meta-database
entries
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Extend to more sophisticated transient analysis