Caltech: Barish, Mours, Shawhan, Whitcomb, Yamamoto, Zweizig
     Carleton: Christensen
     Florida: Klimenko, Rakhmanov
     Glasgow: Drever
     LHO: Gustafson, Ito, Raab, Savage, Sigg
     LLO: Daw, Marka, Weiss
     Loyola: McHugh
     Michigan: Riles
     MIT: Adhikari, Shoemaker
     Oregon: Rakhola
     UTB: Romano

Preliminary E2 Investigation Reports:

• Correlations (N. Christensen reporting)

(See preliminary report web page for details) This study uses DMT software written last year by Adrian Ottewill for quantifying correlations among data channels. Many clear correlations are observed between the GW channel and various other channels over different frequency ranges. Dozens of channels were examined. Plots are shown of correlation strength (0-1) vs frequency. Strong correlations are observed with a number of inteferometer control signals. Nelson solicited advice on what areas to focus on. It was suggested that purely environmental channels be checked for correlation, since cause and effect can be cleanly separated there. Complicating this group's task is the inadvertent mixing of longitudinal control signals during the run by a bug in the controller software (see below).
 
• Data Compression (B. Mours reporting)

(See preliminary report web page for details) Different data compression techniques have been tried on the E2 reduced data set (RDS) channels and statistics compiled. Although the nominal factor of two lossless compression was found for frame-level compression of integers, the compression factor for floating points numbers (which dominate the RDS) was only about 1.3, and the compression algorithm slow. The team also looked at two lossy compression techniques for floats: 1) straight float to int conversion with bit-number control and 2) wavelet compression. The first method is fast, robust, and introduces white noise at a level several orders of magnitude below (present) detector noise for a factor of 2 compression (32->16 bits) and added noise at the few percent level. The second method has the advantage of giving stronger compression (up to factor of 11 for parameters tried) and tunable shape for the added noise. Its disadvantages are slower speed and "touchiness" w.r.t. the character of the data.
In addition, a data summary set (DSS) was produced with statistical information on many channels and selected "raw" data channels. 
Daniel raised some technical issues. He wondered if the data compression could keep up with real-time data taking and whether the benefits of compression were outweighed by the cpu costs of decompression before analysis. Benoit believed the standard method could comfortably keep up with a 20 MB/s data rate. Sergey said the wavelet method could handle a few MB/s on a single processor and suggested multiple processors would be easy to implement. Daniel objected to using a computing farm merely for compression/decompression. He also reminded everyone that AIT tape drives can attain comparable lossless compression at the hardware level "for free", using roughly equivalent techniques. 
Peter stressed that any candidate compression algorithm must eventually be subjected to a test that includes downstream astrophysical source searching.
 
• Information on error signal couplings (R. Adhikari and S. Whitcomb reporting)

(See note for details) Because of an inadvertent coupling of the interferometer length servos (software bug), it is now quite difficult to extract clean measures of error and control signals in the bandwidths of the servos. Although some transfer function measurements were carried out at the time, not enough were measured to permit a complete unfolding of the effects. Stan suggested that above the unity gain frequency of the highest-bandwidth servo, one should be able to extract fairly clean error signals by "inverting" the known software bug. After the meeting Rana provided a matlab template for carrying out such an inverstion.

• The E2 data replay occupied most of John's time in the last month. The replay was done in two batches, for 2-arm and 1-arm data and ran with seven monitors at about three times the real data taking rate. He was not sure what limited that rate, but suspected I/O overhead, despite running off the 1 MB/s RDS instead of the original 3 MB/s raw data.
• During the E2 run 500k 1-second frames were recorded with a few thousand lost due to disk change glitches and the like. There were 211k DMT triggers generated for the meta-database. the 0.4 Hz trigger rate was handled comfortably by the meta-database. About 100 of the triggers were lost initially because of a technical "race condition" which is understood and fixable. A larger fraction of triggers were initially lost from the 1-arm replay because of another technical problem which is also fixable.
• The stability of the sand and stone machines at Hanford seems much improved, and the frame broadcaster was recently replaced, eliminating a choking problem in the data pusher.
• In response to a KR question, John confirmed that trend data can be read with existing DMT infrastructure. Peter reminded everyone that LIGOtools is available for off-site data access, including to trend data.

• Line noise:

 
• B. Allen, A. Ottewill (not present)

 
• S. Klimenko

No news since December teleconference.
 
• A. Sintes (not present)

• Characterizing seismic noise:

• E. Daw
  The band-limited RMS monitor is now fully installed and running under the DMT process manager at both sites (KR note: Hurray!). A problem reported last year with recurring crashes has been fixed with John's help. The monitor is general purpose but will be made easier to use. It now monitors seismic noise in several bands, as described at previous telecons. At Livingston it has been observed that noise in the 1-3 Hz band is correlated with losses of Mode Cleaner locks. Fred remarked that the data being generated at Hanford by the monitor is very nice to have, but that the calibration scale factors seem off. Ed will look into it.  

 
• Inter-channel correlations:

• B. Allen, A. Ottewill (not present)

 
• Bilinear cross-couplings

 
• S. Penn (not present)

 
• Operational state:

 
• D. Chin, R. Gustafson, K. Riles (KR reporting)

Dave has rewritten the OSC package virtually from scratch to make it more flexible and efficient. He is now trying to make it work again and will be at Hanford for three weeks, starting January 15 where he hopes to finish shaking down the new code. New versions of the servo instability monitor and lock loss monitor, which now use the old OSC code, will also be commissioned at Hanford. He will also work on integrating these monitors into Daniel's Monitor Display Manager (MDM) program to allow GUI display of results (and eventually parameter control). Tables and graphs of E2 locked stretches longer than 1 minute have been posted on the Lock Loss Investigation web page, extracted after the recent data replay (see above).

• Bandlimited RMS

 
• E. Daw  (see above)

 
• Time / Frequency plots

 
• S. Mohanty

Not much progress since last month, due to travel. Soumya expects to have his code (relevant to power spectral transients) running by the end of the month.
 
• J. Sylvestre (not present)

 
• Non-Gaussian noise

 
• S. Finn, G. Gonzalez (not present)

• Power spectral transients:

 
• S. Mohanty (see above)

 
• Servo instability:

 
• D. Chin, R. Gustafson, K. Riles (see above)
  
  
• Event catalog:

 
• J. Sylvestre, R. Weiss (not present)

• Flickering optical modes:

 
No volunteer!!!


• Transient detection using adaptive denoising methods

 
• E. Chassande-Mottin (not present)

 
• Impulse recognition:

 
• M. Ito

Masahiro is examining the output of the monitor that was run during the E2 replay, sorting through false alarms to see how to better tune the monitor parameters. A scan of seismic data found four distant earthquakes that appear to have knocked the interferometer out of lock.
 
• Magnetic field transients

 
• R. Frey, R. Rahkola (Rauha reporting)

As reported at the last telecon, a new monitor based on John's PSL monitor is being written. Data from E2 is being studied to determine reasonable thresholds to set for magnetometer channel transients.

A.O.B.

• Next detector characterization teleconference: Friday February 9 at 11:15 a.m. EDT (8:15 PDT).