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S5 BurstMDC simulation

Technical Documentation for the S5 BurstMDC Simulation

Abstract

The S5 BurstMDC Simulation creates frame files with short-duration (<10 s) simulated gravitational-wave (GW) signals for one or more Earth-based GW detectors. These frames are used to characterize the sensitivity of data analysis methods to such signals. The simulation uses external files to define the h+ and hx strain waveforms. Using either specific or randomized sky positions, the simulation projects the waveforms onto the location of the detectors using the existing GravEn simulation engine. The resulting time-series, in either strain or uncalibrated detector outputs, are written to frame files. Log files are compiled to detail the particular simulated injections. Scripts are also provided to carry out large-scale simulation on grid computers.

This simulation has been based at Penn State University. The current maintainer is Keith Thorne. Authors have included Sam Finn, Amber Stuver and Keith Thorne.

This document is intended to describe the analysis procedure and event selection choices in moderate detail, with links to other reference materials containing more detail.

Previous Results

The BurstMDC package was first used to support the S4 Burst Group analysis. Under the S4 BurstMDC web page are links to reports, as well as the S4 MDC sets.

Reports and Presentations

Presentation at June 2005 Burst Group Face-to-Face (LIGO-G050279-00-Z) PDF PowerPoint
Numerous reports to the Burst Group S5 Simulations e-notebook

Software Tools Used

The BurstMDC package includes MATLAB source code and shell scripts.

The latest copy of the MATLAB source code is in the DASWG 'lscsoft' CVS repository, in the /matapps/src/simulation/BurstMDC sub-directory. A draft LIGO Technical Note T070187-00-Z of basic documentation has been prepared. A PDF version is available.

The software uses simple waveform specification and segment list files to generate a Condor DAG pipeline and submit for completion to an LSC grid computer. It creates frame files for an arbitrary network of detectors (typically, H2,H2,L1, GEO, TAMA and VIRGO). At the end, it compiles a master log file describing all simulated signals. It supports both one and two-dimensional waveforms.

There is also web-based documentation. Under the main S5 BurstMDC web page are the following:

This existing documentation was compiled using the old LigoTools release v6r19. This required extensive detail on patching the `mkframe' and `frgetvect' versions. The new v6r24 release has the updated `mkframe' and `frgetvect' routines, but the documentation has not been updated to match.

Reviews

This software has not been reviewed yet. A validation of the antenna factors and polarization conventions was carried out during S4, and is documented on this BurstMDC Validation for S4 web page. The polarization conventions now match those in the LIGO-VIRGO test data and in the Network Simulation package.

Software Versions

The source code and scripts used for production of MDC sets for S5 with S5 V3 calibrations were tagged with BurstMDC_S5_v3 in the matapps CVS. These have been compiled into a source-code/script tar-ball BurstMDC_S5_v3_src.tar.gz and MATLAB executables (version R2006B glnx86) BurstMDC_S5_v3_exe.tar.gz. The source code in this tagged release also has a web-interface

GravEn Simulation Engine

The BurstMDC package relies on the existing GravEn simulation engine to project the waveforms on the the detector locations, prepare time-series data, and convert to uncalibrated detector outputs.

The MATLAB source code is in the DASWG 'lscsoft' CVS repository, in the /matapps/simulation/GravEn. Documentation for the GravEn package (now updated with changes for BurstMDC) was prepared as LIGO Technical Note T040020-03. This is included in the CVS repository and a (PDF Version) is posted here

Reviews

This software was reviewed internally by the Penn State group but has not been reviewed by an LSC search group. A validation effort that led to corrections in GravEn to match the LIGO conventions was conducted during S4. This is summarized on this BurstMDC Validation for S4 web page.

hperasq Calibration Utility

To simplify access to calibration data, the 'hperasq' package returns response functions and &alpha - &beta parameters based upon GPS time, IFO and GW detector channel. There are used by the calibsimfd() and h2asq_fd() function in the GravEn simulation engine.

The published copy of the MATLAB source code is in the DASWG 'lscsoft' CVS repository, in the /matapps/src/utilities/hperasq subdirectory.

There is also web-based documentation of the calibration software for S5 (S5 Calibration page)

The software reads in data from the ASCII-format calibration files provided by the Calibration Group, and supports runs S2 through S5. It has been updated to support the S5 V3 calibration data. It can be customization through the setting of environment variables to specify directories and non-default calibration versions. A caching system is used to reduce the need to re-read data files

Reviews

This software has not been reviewed. Indirect validation occurred for the S4 run through the reconstruction of signal strain values by WaveBurst that had been created with the BurstMDC package. The calibsimfd() function was compared to hardware injections during S4 calibsimfd and HW injections

Known Issues

There are particular issues in simulating gravitational-wave signals that need to be checked for their implementation in the BurstMDC package. These issues include:

Sky Location Randomization

The BurstMDC packages is typically used in all-sky burst searches. It presently picks random sky angles by randomizing cos-theta, phi and psi. It should be checked if that acheives the desired randomization

Time Randomization

When choosing the injection time, BurstMDC spaces things out uniformly by the injection rate, then allow the precise time of each injection to be randomly chosen about that time within 10% of the time between injections.

Antenna Factors

The GravEn simulation engine uses the low-frequency limit so the antenna factors are not frequency-dependent. Grishshuk has argued that even around 1KHz, corrections must be made for frequency-dependence from the transverse components. Rakhmanov has argued that adding the effect of Fabry-Perot arms cancels the largest component of this.

Waveform alignment to channel sample rates

The waveforms in h+ and hx are time-series data, typically at the LIGO sample rate of 16,384. When these are projected onto each detector, the output time-series must be created with some method (interpolation or clamp to nearest sample) to correct for the time shifts.

Handling channels with different sample rates

BurstMDC and GravEn typically output Tama and Virgo at a different sample rate (20,000Hz) than is used for LIGO data (16,484Hz). Is this handled correctly?

Waveform amplitude normalization

When reporting the waveform amplitude, BurstMDC reports h+h+, hxhx and h+hx for use with the antenna factors. This needs to be checked.

Calibration

The conversion to DARM_ERR uses a frequency-domain method (calibsimfd). Is this sufficient?

S5 MDC Sets

The MDC sets generated for S5 are described on the S5 BurstMDC Generation page. For all of S5 are the following: These sets only have strain channels.
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