Median Based Noise Floor Tracker: NoiseFloorMon

The Noise Floor Monitor tracks slow variations or 'drifts' in the noise floor (that
component of interferometric data that is left behind after the lines
and obvious transients are subtracted).  The algorithm implemented by the Monitor
is based on the technique described in the paper
Median based noise floor tracker : robust estimation of noise floor
drifts in interferometric data. S. Mukherjee, Classical and Quantum
Gravity, 20, S925-S936,2003. (download pdf)

Monitor's Output

The output of the monitor is a time series representing the running
median estimate of the second moment. Every time, the output crosses the
three sigma threshold, a trigger is recorded and the data is inferred to
have departed from the stationary behaviour. In each time stride, 60
seconds of raw output are analyzed. Analysis is done separately in four
frequency bands : 0-20 Hz, 20-100 Hz, 100-200 Hz and 200-2048 Hz. The
behavior of the data in these four frequency bands can be seen in the
DMT viewer and is updated every minute. In addition to this, a 12 hour
data trend plot is also available.

The result files record four quantities : the minimum, maximum, rms of
the output and percentage of the data points crossing the threshold in a
one hour period. Those segments that record more than 25% threshold
crossing need further attention and are useful for construction of data
quality flags.

Detector's Lock Condition

The Monitor process the input time series when the detector satisfies the lock condition
"*:Both_arms_locked_strict_cm". If this condition is not satisfied, the Monitor will produce
a zero time series for each band processed.

How To Run the Monitor

The monitor can be run with the following commands :

Monitor Report

Current Running Status
Error Messages