SenseMonitor is a DMT monitor which estimates the range to which the interferometer is sensitive (with SNR > 8) to a standard candle consisting of the inspiral of two 1.4-solar-mass neutron stars. By using online data to estimate this range, SenseMonitor can provide quick feedback to the operators on the performance of the interferometer.
SenseMonitor (v5.0): A Binary-Inspiral Sensitivity Monitor for the DMT
To obtain its data-quality measurement, SenseMonitor relies on the fact that an interferometer with one-sided noise power spectrum PSD(f) is sensitive to binary inspiral events in a volume of space proportional to
The effective range of the interferometer is defined as the radius of a sphere of the same volume; i.e., this range is averaged over all sky positions and binary orientations. To convert SenseMonitor average ranges to the optimally oriented, optimally positioned range used by the inspiral group, multiply the SenseMon range by ~ 9/4 ~ 2.25 ~ sqrt(5).)SenseMonitor evaluates the effective range by computing the AS_Q-strain transfer function (the ``calibration'' or ``response'' function) and applying it to AS_Q data to estimate the strain noise power spectrum PSD(f) of the gravitational-wave channel. SenseMonitor then reports the following:
The principle forms of output are:
- the current range estimate;
- the current amplitude of the calibration line (used to track the interferometer's response function);
- the current values of the calibration parameters `alpha' and `beta' (see the calibration section below).
- a summary web page and shorter `revolver' page available through the CDS homepage;
- the DMTViewer;
- trend files.
SenseMonitor Output
SenseMonitor produces the following output at regular intervals (normally once per minute):Graphical: DMTViewer Plots
The following time series are reported to the DMTViewer (the name of the corresponding channel in the trend files is in parentheses):The following frequency spectra are reported to the DMTViewer only:
- `SNSM EFFECTIVE RANGE (MPC)' (DMT-SNSM_EFFECTIVE_RANGE_MPC):
The average range at which the interferometer can detect the inspiral of a 1.4-1.4 solar-mass neutron-star binary with SNR > 8.- `SNSM CAL LINE AMPL (ASQ)' (DMT-SNSM_CAL_LINE_AMPL_ASQ)
The amplitude of the calibration line as seen in the AS_Q channel. (This is the peak amplitude, which is sqrt(2) times the rms amplitude.)- `SNSM CAL CAV FAC (ALPHA)' (DMT-SNSM_CAL_CAV_FAC)
The value of the calibration parameter alpha. This quantity is computed using the measured calibration-line amplitudes in the AS_Q and excitation (injection) channels, beta as measured from the DARM channels, and the user-supplied reference calibration data.- `SNSM CAL OLOOP FAC (ALPHAxBETA)' (DMT-SNSM_CAL_OLOOP_FAC)
The product of the calibration parameters alpha*beta. This quantity is computed using the measured calibration-line amplitudes in the AS_Q and excitation (injection) channels, beta as measured from the DARM channels, and the user-supplied reference calibration data.
- `SNSM CALIBRATED NOISE SPECTRUM'
This is the strain amplitude noise spectral density (1/sqrt(Hz)) used by SenseMonitor to compute its range estimate.- `SNSM RANGE INTEGRAND (ARB UNITS)'
This is integrand of the integral that gives the range estimate (see the top of this page):f^{-7/3} range_integrand = const x ---------- , PSD(f) range = [ \int df range_integrand ]^{1/2}So, the range is proportional to the square root of the area under the range_integrand(f) curve (on a linear-linear plot!). This can be handy for identifying good and bad noise bands.Interpreting Plots:
SenseMonitor reports zero or negative values for all of these channels under special conditions.
- All Values = 0: The interferometer is not in lock. (SenseMonitor typically requires that the interferometer be running in strict common_mode for it to calculate a range. The precise condition is specified with the -OSCcond option.)
- All Values = -1 or -2: The data for this time is missing. This could be due to a "data dropout", or because SenseMonitor was not running for the period in question. (Check to see if other monitors had dropouts, or look at the SenseMon Error log file.)
When restarted, SenseMonitor fills in the 12hr DMTViewer history with data stored from the previous run of the program. If no such file is found, SenseMonitor initializes its plots with '-1's. Otherwise, SenseMonitor puts a '-2' in the latest data spot as a tag to indicate that the preceeding data was read from a file.
- Alpha = 0 (only): The alpha parameter is calculated from the calibration line, which sometimes is not available. If the computed alpha is not real and positive (which may happen if the calibration line dies) then alpha is reset to zero. The range estimate is then made using the reference response function (alpha=1=beta).
Html and data files
SenseMonitor writes summary log files and other useful data products.
- GDS SPI page. The SenseMonitor links contain summary information, including the range estimates averaged over the last 1, 5, and 15 strides. There are also links to these error and log pages:
- Errors: Shows SenseMonitor's error messages. The most important error messages are about missing data. If lots of data has been lost recently, it is likely that the computer running SenseMonitor is overloaded. Contact your DMT expert.
- Monitor Output: Details of the current run of SenseMonitor, including command line arguments used, and the range and calibration histories. Useful for troubleshooting problems.
- Cumulative Monitor Output: Concatenated log files from ALL runs of SenseMonitor. These can be very large.
- Other: The following files are by default written to the directory specified by the environment variable $DMTHTMLOUT (set to point to a subdirectory of $GDS_APACHE/monitor_reports/ on sand and delaronde). If this environment variable is not set or if the -local option is used, these files are placed in the local directory instead.
- Web Pages: The SPI page html files live here. The top page is index.html; <IFO>_SenseMonitor_Summary.revolver.html is an abbreviated verison.
- 2-Week Summary: The file <IFO>_SenseMonitor_summary.txt contains a two-week summary of the range averaged over 1000-second intervals.
- Calibrated Noise Power: Every 1000 seconds, if the IFO is locked, the current calibrated (strain) noise power spectrum is written to the ASCII file <IFO>_CalPSD_GPS:xxxxxxxxx.txt (eg, L1_CalPSD_GPS:715580020.txt). The latest plots are available from the homepage of the current run.
- Trends: Every hour a trend file is produced showing the minute trends for each of the quantities sent to the DMTViewer. These are available at the sites through LDAS.
Running SenseMonitor
SenseMonitor is managed by the Process Manager, and so it should always be running at the sites. If it is missing, please contact Patrick Sutton or John Zweizig.
The standard way to start SenseMonitor is
SenseMonitor -config <file_name>where <file_name> is a configuration file. Up-to-date configuration files are usually available on the dmt machines (sand, delaronde, etc) as ~ops/pars/SenseMonitor_L1.conf, etc. A sample configuration file for H1 is-OSCfile StateVector.conf -OSCcond Both_arms_locked_strict_cm -xmlfile ReferenceCalibration_H1.xml -fmin 30.0 -trend H1The last entry in the configuration file must be one of H1, H2, or L1. The remaining arguments (which may be invoked in any order) are listed below. Arguments in red are required.
-fmax # Specify maximum frequency to include in range estimate. Default 1400Hz. -fmin # Specify minimum frequency to include in range estimate. Default 20Hz. -h, --help Print usage information, then exit. -local Run in local mode. All output files are dumped in the local directory instead of to the default directory specified by the environment variable $DMTHTMLOUT. The plain-text log file is renamed <GPS_Start_Time>.log. -logfile <name> Name plain-text version of log file <name>. Only works if -local option is also selected. Default filename is <GPS_start_time>.log (-local mode) or <IFO>_SenseMonitor_CumLog.txt (otherwise). -max # Specify maximum number of strides to process before program exits. -n # Specify number of sections to divide data into for calculating the noise power spectrum. The 'stride' variable must be a multiple of this number. Default 15. -OSCfile <file> REQUIRED. Specify the OSC configuration file defining the various operating conditions for the interferometer. (If not specified, SenseMonitor will attempt to open $SENSEMONITOR_OSCCONF/SenseMonitor_LockLoss.conf, then ./SenseMonitor_LockLoss.conf.) SenseMonitor will exit if no OSC configuration file can be found. -OSCcond <cond> Specify the OSC (operating state condition) for which SenseMonitor will compute range estimates. Default is SV_IFO_UP. -screen Update and error messages are sent to the screen instead of to the default files <IFO>_SenseMonitor_Log.txt and <IFO>_SenseMonitor_Errors.txt. -stride # Specify length in seconds of data to use for each range estimate. Default 60. -trend Write range and calibration data to trend files as minute trends. When writing trends it is recommended that `stride' be a factor of 60 (eg: 15, 30, 60). -window <type> Specify data window type for power spectrum estimation, where <type> is one of: `hanning' for Hanning window, `blackman' for Blackman window, `flattop' for FlatTop window (NOT RECOMMENDED), `hamming' for Hamming window (NOT RECOMMENDED), `square' for no window (NOT RECOMMENDED). Default Hanning. -xmlcalREQUIRED. Use dynamical calibration based on a reference calibration file .
Calibration
SenseMonitor estimates the strain noise spectrum from the AS_Q data following the calibration notes of Gonzalez et al (2002, 2003). All actual calibration calculations are performed by the FDEasyCalibrate class, which requires as input a specially formatted file containing reference calibration information. These reference calibration files will be produced by the calibration team. The only point that might interest the casual user is that this calibration data should be linearly sampled over a frequency range larger than [fmin,fmax] Hz (see -fmin, -fmax options) and not including 0 Hz or 4096 Hz. SenseMonitor will exit if the calibration data does not cover [fmin,fmax] Hz.Operating State Condition (OSC)
SenseMonitor requires a file defining the condition under which range estimates will be computed. A good choice for OSC (-OSCcond) is Both_arms_locked_strict_cm. In this case the detector is required to be in common mode, but not necessarily in science mode. A good choice for the definitions file (-OSCfile) is D. Chin's /export/home/ops/pars/LockLoss.conf, which contains up-to-date definitions of standard states.The user may specify an alternative location and file name at launch. Otherwise, SenseMonitor will search for the file SenseMonitor_LockLoss.conf, first in the directory specified by $SENSEMONITOR_OSCCONF and then in the local directory. You can (re-)set the environment variable SENSEMONITOR_OSCCONF using a command like
setenv SENSEMONITOR_OSCCONF directory_pathKnown Bugs
- None.
Contact Info
Comments, queries, and suggestions regarding any aspect of SenseMonitor are welcome; please email the authors.
Authors: Kevin C. Schlaufman Patrick J. Sutton Code Version: 5.0; last modified Oct. 23 2004. Documentation: last modified Oct. 23 2004.