1 / 25

Introduction to QScan

QScan is a powerful tool for detailed analysis of auxiliary and environmental channels related to detector activity such as glitches and gravitational-wave events. This tool provides support for commissioning, veto search, and more. Explore its features and applications.

bgoldberg
Download Presentation

Introduction to QScan

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Introduction to QScan Shourov K. Chatterji SciMon Camp LIGO Livingston Observatory 2006 August 18

  2. QScan web page • Much of this talk is taken from the QScan web pagehttp://www.ligo.caltech.edu/~shourov/q/qscan/ • Overview • Example scan • Interpretation of scans • Quick start guide • Configuration details • Source code • Installation and testing • Existing installations Introduction to QScan, LLO, 2006 August 18

  3. QScan overview • QScan is a tool to perform a detailed study of a very large number of auxiliary and environmental channels around a specific time of interest • Detector glitch • Hardware injection • Candidate gravitational-wave event • It currently provides support for a number of activities • Commissioning • Detector characterization • Veto search • Astrophysical searches Introduction to QScan, LLO, 2006 August 18

  4. QScan overview (cont.) • QScan is based upon the Q Pipeline burst search algorithm • Multiresolution time-frequency search for statistically significant excess signal energy • Projects whitened data onto the space (time, frequency, and Q) of Gaussian windowed complex exponentials • Equivalent to a matched filter search for waveforms that are sinusoidal Gaussians after whitening • Significance is characterized by normalized energy Z • 2Z is equivalent to the squared signal to noise ratio of a matched filter search • Details provided in http://ligo.mit.edu/~shourov/thesis/ Introduction to QScan, LLO, 2006 August 18

  5. QScan overview (cont.) • The search space is covered by • Logarithmically spaced Q planes • Logarithmically spaced frequency rows • Linearly spaced tiles in time Introduction to QScan, LLO, 2006 August 18

  6. Example Q transform 20% loss, Q of 4 1% loss, Q of 4 poor match 20% loss, Q of 8 1% loss, Q of 8 best match Introduction to QScan, LLO, 2006 August 18

  7. Example QScan • QScan produces web based reports that include • event time in GPS, UTC, PST/PDT, CST/CDT • science and injection mode segments • data quality segments • links to detector logs for day of event and next day • Index of channels by subsystem • channel names link to channel wiki • time series and time-frequency spectra • quantitative summary file for automated followups • log file for containing debug information • space for additional information • Example QScan of a inspiral hardware injection Introduction to QScan, LLO, 2006 August 18

  8. Interpreting QScans Channel namelinks toChannelWiki Display time series,spectrograms, oreventgrams Most significanttile propertiesin search window Introduction to QScan, LLO, 2006 August 18

  9. Interpretation (cont). • Only statistically significant channels are displayed • Significance level defined in configuration file • Channels tested for significance in a finite time window • Time window duration defined in configuration file • Typically on the order of one second • Accurate timing is required before running a QScan • Absence of a channel does not imply no significant content • Presence of a channel does not imply correlation with signal in the gravitational-wave channel • QScans at random times can give some guidance • QScan is not a substitute for a continuous search Introduction to QScan, LLO, 2006 August 18

  10. Interpretation (cont.) • Multiple image products are produced • Time series (raw, high pass filtered, whitened) • Spectrograms (raw, whitened, autoscaled) • Eventgrams (raw, whitened, autoscaled) • Each image type has its advantages and disadvantages • It is important to use all types to correctly interpret scans Introduction to QScan, LLO, 2006 August 18

  11. Time series images • Raw, high pass filtered, and whitened time series • Useful for diagnosing saturation, bit level noise, or otherwise broken channels. • Raw data may be downsampled • Downsampling in reduced data sets • Downsampling in QScan • May obscure otherwise obvious saturations • High pass filter frequency specified by configuration file • Whitening performed by zero-phase linear prediction • Parameters determined from configuration file • May introduce artifacts (particularly echoes) Introduction to QScan, LLO, 2006 August 18

  12. Time series examples Inspiral and pulsarhardware injectionsbefore and afterwhitening Bit level noise inbroken channel Saturatingchannel Introduction to QScan, LLO, 2006 August 18

  13. Spectrogram images • Spectrograms are produced at constant Q • All tiles have same bandwidth to central frequency ratio • QScan displays the Q plane with the most significant tile • This choice of Q may obscure features that best match other values of Q • Spectrograms are produced with and without zero phase linear predictive whitening • Linear predictive whitening may produce artifacts • Even without linear predictive whitening, QScan normalizes by the mean energy in each frequency row • Spectrograms are produced with both fixed and autoscaled colormaps to see both very significant structure as well as weaker but perhaps still siginificant nearby features Introduction to QScan, LLO, 2006 August 18

  14. Spectrogram examples raw whitened autoscaled Introduction to QScan, LLO, 2006 August 18

  15. Eventgram images • Eventgrams display information from all Q planes • Identify significant tiles by thresholding on significance • Project all tiles onto the same time-frequency plane • Remove the less significant of overlapping tiles • Produces a “mosaic” like tiling of the signal • Gives Q independent picture of signal • But it is more difficult to identify subtle structure • Similar to spectrograms • Eventgrams are produced with and without zero-phase linear predictive whitening • Eventgrams are produced with both fixed and autoscaled colormaps Introduction to QScan, LLO, 2006 August 18

  16. Eventgram examples raw whitened autoscaled Introduction to QScan, LLO, 2006 August 18

  17. Different time scales • Specified by configuration file • Identify small time-scale features near time of event • Larger time scales provide context information • How isolated is the glitch? • How significant is the glitch relative to nearby structure? • Is signal coincident with the gravitational-wave channel or is it glitching all the time? • QScan provides guidance for more extensive veto studies • Note that the finite resolution of images limits the ability to resolve short transients in long time scale images Introduction to QScan, LLO, 2006 August 18

  18. Quick start • The quickest way to get started is to use the existing QScan installation and default configuration at one of the LIGO Laboratory computing clusters:grid-proxy-initssh ldas-pcdev1.ligo-wa.caltech.edu~qonline/qscan/bin/qscan.sh 816335770.0 & • The QScan launch script can also be given a custom configuration file, frame cache file, and output directory:qscan.sh gpstime <configuration> \ <framecache> <outputpath> Introduction to QScan, LLO, 2006 August 18

  19. Configuration • Automatic configuration utility qconfigure.sh • Uses FrChannels to scan an example frame file • Makes educated guess at configuration parameters based on channel name and sample frequency • End users can edit the resulting congifuration files • A large number of standard configuration files (@gw, @H0H1H2-RDS_R_L1-selected, etc.) are provided • Gravitational-wave channels only • Level one reduced data set • Raw data set • Time-domain calibrated data • Seismic channels only • Different detector networks • etc. Introduction to QScan, LLO, 2006 August 18

  20. Configuration example [Gravitational,Gravitational wave data] { channelName: L1:LSC-DARM_ERR frameType: RDS_R_L1C sampleFrequency: 4096 searchTimeRange: 64 searchFrequencyRange: [32 Inf] searchQRange: [4 64] searchMaximumEnergyLoss: 0.2 whiteNoiseFalseRate: 1e0 searchWindowDuration: 0.5 plotTimeRanges: [1 4 16] plotFrequencyRange: [] plotMaximumEnergyLoss: 0.2 plotNormalizedEnergyRange: [0 25.5] } Introduction to QScan, LLO, 2006 August 18

  21. Data discovery • Data is located using framecache files • Framecache files produced by createframecache.plcreateframecache.pl framecache.txt \ frameFileDirectory • Predefined framecache files are provided for commonly used data sets (@gw, @S5-RDS_R_L1, etc.) • LHO and LLO scans for recent events automatically find raw frame data from /frames • S5 framecache files are currently updated once per day • Working on LSCdataFind or LDAS frame cache interface Introduction to QScan, LLO, 2006 August 18

  22. Segments and data quality • Science mode, injection mode, and data quality segment information is taken from daily dumps of the LSCsegFind database • There is a ~1 day latency on this information • Shows up as “unknown” if not yet available • Data quality segment definitions also change over time • The qupdate.sh script can update segment and data quality information without rerunning the entire scanqupdate.sh ~/public_html/qscans/ 816335770.0 Introduction to QScan, LLO, 2006 August 18

  23. Infrastructure • QScan is written in Matlab • Shares common code base with Q Pipeline • Uses FrameL based access to frame files • Uses Matlab compiler to produce a stand-alone executable that is free from license restrictions • Currently uses Matlab version R13 • Requires X server to produce figures • Supports multiple platforms • Fedora Core 3 and 4 • Solaris 9 and 10 • Installed on CIT, LHO, LLO, MIT, PSU, and UWM clusters • Installed on CIT, LHO, LLO, and MIT general computing • Can be run under condor on LSC computing clusters Introduction to QScan, LLO, 2006 August 18

  24. Current use • S5 glitch search • Loudest single detector inspiral events • Loudest single detector blocknormal events • Loudest H1H2 kleineWelle events • S5 burst search • Produced for candidate WaveBurst events • S5 inspiral search • Incorporating into automated follow-up of candidates • S5 operations and commissioning • Available in LIGO control rooms • In use by both operators and commissioning teams Introduction to QScan, LLO, 2006 August 18

  25. Room for improvement • QScan is computationally intensive • Requires a while to run (~1 hour for raw data scan) • Requires a lot of disk space (~? GB for raw data scan) • Slow to load (~1 minute for raw data scan) • Data discovering could be more automated • Currently updating frame cache once per day • Planned interface to LSCdataFind and LDAS disk cache • Requires accurate knowledge of event time • Implementing initial prescan to identify glitch time • Provide graphical user interface to run QScans • Provide calibrated output for channel coupling studies • Provide easier access in control rooms • Provide larger collection of specialized configurations Introduction to QScan, LLO, 2006 August 18

More Related