O4 Alternate Strain Release

Overview

This data set includes several versions of the strain channel recorded during the O4 observing run. For context, see the O4a 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:GDS-CALIB_STRAIN_CLEAN_AR', start=1368980000, end=1368980010, host='nds.gwosc.org')

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 OSDF.

To set up OSDF on your computer, see OSDF 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)

To search for public data OSDF file URLs, one may use gw_data_find for a given frame and segment interval:

gw_data_find -r datafind.gwosc.org -o H -t H1_HOFT_C00_AR -s 1368980000 -e 1368980010 -u osdf

Alternatively, in python code, to download OSDF url files for a given frame type and GPS segment:

import os
import requests_pelican as rp
from gwdatafind import find_urls

url = find_urls("H", "H1_HOFT_C00_AR", 1368980000, 1368980010, urltype='osdf', host="https://datafind.gwosc.org")

with open(os.path.basename(url[0]), mode="wb") as file:
    file.write(rp.get(url[0]).content)

Segments

Download CSV Segment Lists:

ER15: H1 - L1
O4a: H1 - L1

Usage notes

For ER15, all data marked as COINC are included in the release. However, the files also contain segments not marked as COINC. Such segments should not be used for analysis.
For O4a, all data marked as ANALYSIS READY are included in the release.

Available Channels

Frame Type	Channels	Notes
H1_HOFT_C00_AR L1_HOFT_C00_AR	`H1:GDS-CALIB_STRAIN_AR` `L1:GDS-CALIB_STRAIN_AR`	Calibrated strain data with no cleaning
H1_HOFT_C00_AR L1_HOFT_C00_AR	`H1:GDS-CALIB_STRAIN_NOLINES_AR` `L1:GDS-CALIB_STRAIN_NOLINES_AR`	Calibrated strain data, after applying narrowband noise subtraction.
H1_HOFT_C00_AR L1_HOFT_C00_AR	`H1:GDS-CALIB_STRAIN_CLEAN_AR` `L1:GDS-CALIB_STRAIN_CLEAN_AR`	Calibrated strain data, after applying both narrowband and broadband noise subtraction. This is the recommended channel for transient searches.
H1_HOFT_C00_AR L1_HOFT_C00_AR	`H1:GDS-GATED_STRAIN_AR` `L1:GDS-GATED_STRAIN_AR`	This is the `H1:GDS-CALIB_STRAIN_NOLINES_AR` (resp. `L1:GDS-CALIB_STRAIN_NOLINES_AR`) channel where times with loud glitches are replaced with zeros by applying a window function around short segments of elevated noise. This channel was not used for analyses by the LVK collaboration.