Gravitational Wave Open Science Center

O3a Alternate Calibration Release


This data set includes several versions of the strain channel recorded during the LIGO/Vigo O3a observing run. For context, see the O3a data release documentation.

Data Access

Single Computer Access

For work on a single computer, data may be accessed from a network data server (NDS2) using the NDS2 client or GWpy:
from gwpy.timeseries import TimeSeries
data = TimeSeries.fetch('H1:DCS-CALIB_STRAIN_CLEAN_C01_AR', start=1240559616, end=1240559626, host='')
For more examples of working with the NDS2 server, See the NDS2 Example Code.

Computer Cluster Access

For users of computer clusters, data are available via CVMFS.
  • To set up CVMFS on your computer, see CVMFS instructions.
  • If you are working on a computer cluster which already has access to LIGO/Virgo data, see accessing IGWN data.
  • Data gaps represent times when data are not available (e.g. the instrument was not running)


Download CSV Segment Lists: H1 - L1 - V1

Usage notes

  • For LIGO, all data marked as ANALYSIS READY are included in the release.
  • For Virgo, all data that passes CAT 1 data quality are included in the release.
  • A small amount of time around GW190814 is missing from the channel H1:DCS-CALIB_STRAIN_CLEAN_SUB60HZ_C01_AR, because these times were initially marked outside of observing mode
    • Missing segments: [1249847058, 1249851715) [1249852276, 1249852862)
  • The Timelines DATA segment list only includes times that pass CAT 1 data quality. For some times, LIGO data may be available in this multi-channel release, but not included in the Timeline segment lists.

Available Channels

Frame Type Channels Notes
C01 calibrated strain data (final calibration)
C01 calibrated strain data, after applying linear noise subraction
C01 data, after applying both linear and non-linear noise subtraction. For LIGO O3a data, this is the recommended channel.
V1Online_AR V1:Hrec_hoft_16384Hz_AR Virgo data for most of O3a
V1O3Repro1A_AR V1:Hrec_hoft_V1O3ARepro1A_16384Hz_AR Only available for the last two weeks of September 2019. The reprocessing was motivated by an improvement of the noise subtraction with respect to the changing ITF working point during tests of Etalon effect control.