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Minutes of 2008-Jul-17 S5 QPipeline Review Teleconference


Shourov Chatterji, Jonah Kanner, Isabel Leonor, Dave Reitze

Minutes by Isabel Leonor.




* Announcement

  Dave:  Next week might not be good time for telecon.

* Discussed table that Jonah created which summarizes things to be done to 
  finish review:

  Jonah leads discussion.

* Whitening

  Jonah:  Concerned this has not been discussed enough.

  Isabel:  What's in Chapter 4 of Shourov's thesis is implemented in Shourov's
           code.  Has also run the whitening code and confirms it does whiten data.

  Jonah:  I need to read and understand Chapter 4 then.

  Dave:  Has read Chapter 4.  Jonah only needs to convice himself after reading
         Chapter 4.

  Shourov:  The whitening implemented is a tried and true technique.  Prior
            implementation has also been used by other analyses, e.g.  

  Dave:  What can go wrong?

  Shourov:  Need to pick filter length to be longer than data segment.  Narrow 
            lines will still appear if long FFTs are taken.

            h(t) data has large increase at low frequencies due to seismic wall.
            This causes dynamic range problem for whitening.  Solution is to
            highpass-filter before whitening.

            Phase delays are avoided by implementing zero-phase method.

* H1H2 coherent transform

  Jonah:  Concerned that implementation is not fully understood by reviewers and
          that this needs further documentation.  Isabel, can you explain this
          to us?

  Isabel:  Will try to document this.

  Dave:  Shourov, can you add links to documenation to this table?

  Isabel:  Notes that there is already documentation in the technical document

* Null stream veto

  Jonah:  Wants additional documentation on null stream inflation factor.

* Coincidence

  Jonah:  Verification of Shourov's scripts has been done with Laura's scripts.  
          Shourov, walk us through how these were verified.

  Dave:  Are live times the same as for cWB analysis?  Same DQ flags?

  Shourov:  There are minor differences due, for example, to differences in
            minimum segment durations.

            In combining results, take union, not intersection, of live times.
            There are only minor deviations.  Should be verified.

  Jonah:  We need list of all postprocessing scripts and to do some sort of 
          verification.  Shourov, if I poke through the directory [see links in
          table], can I figure out which scripts were used?

  Shourov:  There is C++ library used for coincidence, overlap, thresholding.
            There are also simple shell scripts, awk.

  Jonah:  Tempted to poke around and check.  I might learn something.

  Isabel:  How many post-processing scripts are there?

  Shourov:  A lot of small scripts.

  Jonah:  A list of these scripts is necessary.

  Isabel:  Agrees that a list is necessary.  Are these scripts in CVS?

  Shourov:  Not sure.  The rerun (injections) was more organized, so will point
            to those scripts.

  Dave:  Modify table.  Shourov to make sure that scripts are in CVS.

* Thresholds

  Jonah:  Sent around document with sensitivity estimate.  Not sure if it's 
          right.  Shourov sent an email around.

  Shourov:  Use average instead of best performance curves.  Did study using
            1000 4-sec long segments throughout year, then average spectra.  
            Resulting average was similar to best noise curves, which was 

            Patrick suggested that, instead of averaging S, take average of 1/S,
            then calculate 1/<1/S>.  Resulting spectrum is a factor of 2 lower.

  Dave:  Try another random 1000 segments.  Average shouldn't go down with
         second method.

  Shourov:  It's possible there was a mistake.

            Possible option, used in S3 to determine threshold of detectability:
            Look at each injection and calculate power spectrum at time of
            injection, and evaluate SNR integral for that injection.  Then 
            create table of detection/non-detection; this determines SNR

  Dave:  Regarding Jonah's calculations, numbers are not crazy.  SNR of 12.

  Jonah:  Overestimated H2.

  Shourov:  Might also look at documentation for coherent follow-up.

  Jonah:  One question regarding QPipeline normalized energies.  Are correlated
          energies normalized by coherent energy values?

  Shourov:  Correlated energy is not like other energies.  Can't answer that
            question right away.

  Jonah:  Should get written down somewhere.

* Loud events

  Jonah:  What's on table?

  Dave:  Why the loudest events table?

  Shourov:  Had initially planned loudest event analysis instead of using 
            threshold.  Part of motivation was lost when we switched to 
            counting statistics.

  All:  We all agree that manually examining a table of 100 loudest events is
        excessive and unnecessary.  A table of the 10-20 loudest events is more

* Outstanding items

  Jonah:  At some point, we need to see if we still care to get these things 
          What do we need to do with frequency-dependent results?

  Isabel:  I think the frequency-dependent results make sense.  Once
           thresholds are chosen, what we get is what we get.  Just need to
           compare these results to those of other analyses and point this
           out to general review committee.

  Jonah:  We need to go back and see what we really want Shourov to do.

  Dave:  Propose different meeting time next week:  Monday, July 28, 1 PM PDT.
         I'm working on assignments for review document.  Will circulate next

Action Items

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