Soma Mukherjee, GWDAW7, Kyoto, Japan, 19/12/02, LIGO-G Z1 Robust Detection of Noise Floor Drifts in Interferometric Data Soma Mukherjee Max Planck Institut fuer Gravitationsphysik Golm, Germany. GWDAW7, Kyoto, Japan, 19/12/02

Soma Mukherjee, GWDAW7, Kyoto, Japan, 19/12/02, LIGO-G Z2 Motivation : Interferometric data has three components : Lines, transients, noise floor. Study of a change in any one of these without elimination of the other two will cause interference. Lines dominate. Presence of transients change the central tendency. “SLOW” nonstationarity of noise floor interesting in the analysis of several astrophysical searches, e.g. Externally triggered search.

Soma Mukherjee, GWDAW7, Kyoto, Japan, 19/12/02, LIGO-G Z3 Methods : Running Median. Computation of : G(m)=V(Z t+m – Z t )/V(Z t+1 – Z t ) Z t : t th sample of a timeseries. m: Lag.

Soma Mukherjee, GWDAW7, Kyoto, Japan, 19/12/02, LIGO-G Z4 Sequence : Low pass and resample Estimate spectral noise floor using Running Median Design FIR Whitening filter. Whiten data. Clean lines. Highpass. Compute Running Median of the squared timeseries. Construct Variograms. Thresholds set by Simulation.

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Soma Mukherjee, GWDAW7, Kyoto, Japan, 19/12/02, LIGO-G Z19 Future : `To be run on full S1 data (LIGO/GEO). More quantification of the Running Median and variogram. To be tested on bandlimited data. Automation and incorporation in the DCR underway.