Results of Running SLOPE for the h(t) Noise Comparison
H1, First Epoch
PRELIMINARY

SLOPE is currently being run over the FFT(h(t))/h(f) ratios to identify times in the data where this ratio differs significantly from the rest of the data.  This ratio data is computed using 60 second averages and evenly sampled frequency bandwidth between 100 Hz and 300 Hz.

SLOPE is a redeveloped (from S1) Burst Event Trigger Generator.  Given a specified window (data) length, SLOPE will calculate the best linear trend to that data.  The starting point is then incremented a sample and the process is repeated until the end of the data is reached.  Triggers are determined based on a probability threshold that a given measured slope is NOT accidental for white noise statistics.  Therefore, if a threshold of 0.9 is given, then we expect a false trigger for every 10 triggers.

For this purpose, SLOPE is run in each frequency bin (SLOPE needs white data to operate on which is the case within the frequency bins because this data should represent a random fluctuation).  The results are then collected and the excess SLOPE energy in each time bin is calculated.  Excess SLOPE energy is defined to be the sum of the ratios of the measured slope for a trigger to the minimum slope needed to pass threshold.  The time bins with the largest excess energy are of the most concern to this investigation.

The SLOPE parameters used in this investigation is: window size = 3 (this give the first centered derivative calculation) and threshold = 0.99.

For the H1's first calibration epoch, the most significant times are shown below:

1st and 2nd most significant:

GPS times: 820425815 & 820425695
Closest time identified using the strongest pixel method: 820425755  spectrogram  q scan



3rd and 4th most significant:

GPS times: 817939576 & 817939456
Closest time identified using the strongest pixel method: 817946173  spectrogram  q scan




5th and 6th most significant:

GPS times: 821462696 & 821462576
Closest time identified using the strongest pixel method: 821462636  spectrogram  q scan



Summary:

It should be noticed that while this method does not yield the exact same results as the strongest pixel method, on a superficial level the most significant times are similar.  This indicates that this SLOPE investigation is on target for looking for times that differ the most from the other times.  The differences between this method and the strongest pixel method give different ranks to the most significant events. 

I am currently investigating the times that have excess energy in them but are not the strongest.  I hypothesize that the differences between the methods will become more apparent since it is not what a single pixel strength is that is being measured but the contribution of triggered pixels throughout the time bin.  So, while no one pixel may be that significant by itself, in this SLOPE method the sum of less significant pixels may bring more subtle h(t) noise issues to light.