The S6 Data Release

Run Overview

Data Quality

LIGO data quality categories, or flags, are defined by each data analysis group: Compact Binary Coalescence (CBC), Burst, Continuous Waves (CW), and Stochastic for their analyses. For each flag, LOSC data files contain a corresponding 1 Hz channel that marks times that pass the flag as a "1" (good data), and times that fail the flag as a "0" (bad data). A full list of S6 data quality categories can be seen on the S6 channel definitions page. The details of each category are described in the references linked below. However, as a rough guide:
  • DATA (Data Available): Failing this level indicates that LIGO data is not available at this time.
  • CAT1 (Category 1): Failing a category 1 data quality check indicates a severe problem with the data. Times that fail CAT1 flags should not be searched for astrophysical signals.
  • CAT2 (Category 2): Failing a category 2 data quality check indicates there was a major instrumental problem at the time of data collection
  • CAT3 (Category 3): Failing a category 3 flag indicates a moderate concern or possible problem at the time of data collection. These are typically linked to times of statistically identified problems.

In general, data quality levels are defined in a cumulative way: a time which fails a given category automatically fails all higher categories. For example, if the only known problem with a given time fails a burst category 2 flag, then the data is said to pass DATA and BURST_CAT1, but fails BURST_CAT2 and BURST_CAT3.

More information on data quality can be found in these locations:
  • Step 3 and Step 4 of the introductory tutorial show how to apply data quality flags
  • Channel definitions for the S6 data set.
  • Technical details about these data quality categories, of interest to LSC members, can be found here, under "S6 DQ flags".

Data quality category definitions are described in the associated publications. Each paper is also available as a free preprint from

Instrumental Spectral Lines

A power spectral density of LIGO data typically shows a number of spectral lines. Many of these are associated with known instrumental resonances. See the S6 Instrumental Lines page for details.

Technical Details

LOSC strain data have been repackaged and downsampled from 16384 Hz to 4096 Hz.
More detailed information about the data set can be seen on the Technical Details page.

Hardware Injections

The S6 data set contains simulated astrophysical signals, known as hardware injections, used for testing and calibration. The simulations represent the types of signals sought by each of the four LIGO data analysis working groups. Documentation on working with hardware injections can be seen in the Find a Hardware Injection Tutorial. Complete documentation of these "hardware injections" can be found by following the links below:

Get S6 Data


To acknowledge the use of S6 data, see the Acknowledgement Page.

Data Set DOI: 10.7935/K5RN35SD