Gravitational Wave Open Science Center

S5 Burst Hardware Injections

Hardware Injections

During LIGO's 5th Science Run (S5), simulated signals were added to the LIGO detectors for testing and calibration. The simulated signals are known as hardware injections, because they were created by manipulating mirrors in the arms of the interferometers. Times of hardware injections are marked in LIGO data files by injection data quality channels. See the injection bit mask definition for details.

Burst Injections

Burst injections were added at planned times throughout S5. Burst injections were injected with the following waveforms. In addition, some notes about Burst waveform generation and naming conventions can be found on Alan Weinstein's home page.

Sine-Gaussians (sg*Q9)

The plan called for sine-Gaussians at 70, 235, 914, and 2000 Hz. An example Sine-Gaussian waveform and spectrogram can be seen in the images on this page.

Gaussian (ga*)

Gaussian waveforms with various values of the width, Tau. The number following "ga" indicates with width of the Gaussian in units of 1e-4 seconds. For example, ga0010 indicates a Gaussian waveform with a width of 1 ms.

Zwerger-Mueller (zmA3B3G1)

This is a waveform based on supernova simulations described in (Zwerger & Mueller, 1997) Catalog waveform A3B3G1, with minor tweaks to get rid of the small discontinuities at the beginning and end.

Ringdown (r2600t300)

Damped sinusoid with a frequency of 2600 Hz and a decay time of 300 ms. To avoid an abrupt beginning, it includes an exponentially growing (time scale 30 ms) sinusoid at the beginning. This waveform is rather long, so it is in a waveform file 4 seconds long. (All other waveforms are in one-second-long files.)

Cosmic string cusp (cusp220)

Generated by calling the function cuspgw.m, with a cutoff frequency of 220 Hz.

Band-limited white noise burst (wnb250bw100dt30)

These have a specified central frequency and bandwidth and have a Gaussian envelope in the time domain with a specified sigma. They use a central frequency = 250 Hz, bandwidth = 100 Hz, and sigma = 30 msec. The plan called for the signal to have two polarization components, to give somewhat different waveforms at LHO and LLO. We generated separate white-noise bursts and then took linear combinations to yield a fixed coherence of 0.7 .

Lists of Injections

S5 Burst Injection Lists: H1 H2 L1
Each list includes a nearly complete list of the planned Burst injections in S5. Exceptions include the blind injections (noted above) and a small number of injections marked in the Timeline segments (noted below). Each row of the table represents one injection. Each row includes the following information:
  • The GPS time of the injection
  • The waveform name of the injection
  • A scale factor, indicating the hrss of the injection in units of 1e-21
  • A log message indicating the success or failure of the injection
  • The expected SNR of the injection
  • The recovered SNR of the injection, as measured by a matched filter
Injections typically occur in groups, with between 3 and 36 injections in each group.

Timeline Segment Lists of Injections

In addition to the log files shown above, information about injection times is available in segment lists from the Timeline application.
  • The HW segment lists contain all Burst, CBC, and Stochastic injection times: H1 H2 L1
  • The HW segment lists contain a small number of injections not noted in the Burst or CBC logs: H1 H2 L1
  • The HW_BURST segment lists contains only the times of the Burst "Blind Injections", described above.

Blind Injections

In addition to the burst injections noted in the tables below, there were 2 periods of "blind injections" in S5.

Blind Injection Testing: 872452814-872453714 (August 29, 2007, 13:00 - 13:15 PDT)

H1/H2/L1 872452814-872453714 (August 29, 2007)
   H1/H2/L1 872452814 (13:00PDT 
   H1/H2    872453114 (13:05PDT)
   H1/H2    872453414 (13:10PDT)
   Three successive burst injections were attempted on
   all three IFO's were attempted, but an error caused
   the 2nd injection to knock L1 out of lock. So only the
   1st of its injections was in science mode. For simplicity,
   15 minutes in total are flagged here for all three IFO's.
Burst blind injection 874465554.715 (Sep 22 2007 03:05:40 UTC) A single, coherent blind injection in all 3 LIGO instruments. This is the so-called "equinox event", which is described in the book Gravity's Ghost, by Harry Collins.

Technical Details

More information on Burst hardware injections is avaialable on the Technical Details page.