Tutorial: Generation of simulated data

Introduction

GstLAL provides several tools for producing fake gravitational wave data for the purpose of simulating various scenarios. This page works through several examples starting with simple command line data generation, working up to Condor DAGs that can generate months of fake data suitable for MDC studies.

Basic LIGO/ALIGO colored Gaussian noise on the command line

Consult gstlal_fake_frames for more details

The basic steps to generate and validate LIGO colored noise are:

  1. Use gstlal_fake_frames to make the data

  2. Verify that the PSD is as you would expect with gstlal_reference_psd

  3. Plot the resulting PSD with gstlal_plot_psd

An example PSD plot:

../_images/H1L1fakedataexamplepsd.png

Custom colored noise, i.e. simulate your own detector

Consult gstlal_fake_frames for more details

  1. Start by obtaining a reference PSD that you wish to have as the target for recoloring. If you actually have a text file ASD such as this one: e.g. here, then you will need to first use gstlal_psd_xml_from_asd_txt to convert it

  2. Next use gstlal_fake_frames to make the data with the desired PSD

  3. Repeat the same validation steps as above to obtain, e.g.:

../_images/V1fakedataexamplepsd.png

Recolored noise

Consult gstlal_fake_frames for more details

This procedure assumes you are on an LDG cluster which has the data you wish to recolor. Note that some of the tools required on not gstlal based. Please consult the documentation for the external tools should you have questions.

  1. First obtain segments for the data using ligolw_query_gwosc_segments

  2. Then create the PSD you wish to recolor to (perhaps using gstlal_psd_xml_from_asd_txt)

  3. compute a reference spectrum from the strain data that you wish to recolor using gstlal_reference_psd

  4. You might choose to optionally “smooth” the reference spectrum in order to leave lines in the underlying data. You can try using gstlal_psd_polyfit

  5. Now with segments, a PSD (possibly smoothed) measured from the strain data, and a PSD that is the target for the recolored spectrum, you are free to use gstlal_fake_frames according to the documentation.

Recoloring existing data with a HTCondor dag

Some of the steps required to automate the batch processing of recoloring a large data set has been automated in a script that generates a condor DAG. The input to the condor dag script has itself been automated in makefiles such as this.

As an example try this:

$ wget https://git.ligo.org/lscsoft/gstlal/raw/master/gstlal/share/Makefile.2015recolored
$ wget https://git.ligo.org/lscsoft/gstlal/raw/master/gstlal/share/recolored_config.yml
$ make -f Makefile.2015recolored
$ condor_submit_dag fake_frames_dag.dag

You can monitor the dag progress with:

$ tail -f fake_frames_dag.dag.dagman.out

You should have a /frames directory that contains the recolored frame data. Experiment with changing parameters in the Makefile to generate different PSDs, create frames over different stretches of data, etc.