IGWN data are stored in a number of locations, and what data are available is dependent on how the data should be accessed.
For file-based access, including using CVMFS, see Dataset discovery.
For direct access to (remote) specific data channels, without using files or datasets, see Remote data discovery with NDS.
Datasets archived in files should be discoverable using GWDataFind, an HTTP-based API to the index of available files for a given computing centre.
Data are indexed using the following metadata parameters:
observatory- the single-character prefix for the observatory
frametype- the dataset name
- the GPS
[start, stop)interval of the contained data
For more details, and better examples, about the GWDataFind client, see
For a full description of the GWDataFind HTTP API, see
Distributed data server¶
An instance of the GWDataFind server is operated centrally to support discovery of any data distributed using CVMFS.
This instance should be used for all offline analysis of data by IGWN members.
The address of the service is
Requires SciToken authorisation
This service requires SciToken authorisation.
Each computing centre operates its own GWDataFind server to enable discovery of its available data. The address of the server will be automatically configured in the following shell envirnoment variable
which the GWDataFind client will automatically use.
No authorisation required for local access
The local GWDataFind servers are usually configured to accept connections without authorisation from other hosts on the same network.
To discover which datasets are available at a given location for an observatory:
from gwdatafind import find_types print(find_types("L"))
python3 -m gwdatafind -o L --show-types
Discovering data URLs¶
The GWDataFind servers will return URLs for specific data files.
The default response when using the client library is to return
Discover file URLs
To find the
file:// URLs (or paths) for a dataset:
from gwdatafind import find_urls print(find_urls("L", "L1_HOFT_C00", 1187008866, 1187008898))
python -m gwdatafind -o L -t L1_HOFT_C00 -s 1187008866 -e 1187008898
A GWDataFind server can also return
osdf:// URLs, intended to work with HTCondor file transfer:
Discover OSDF URLs
To find the
OSDF:// URLs for a dataset:
from gwdatafind import find_urls print(find_urls("L", "L1_HOFT_C00", 1187008866, 1187008898, urltype="osdf"))
python -m gwdatafind -o L -t L1_HOFT_C00 -s 1187008866 -e 1187008898 -u osdf
Only works with CVMFS paths
A GWDataFind server can only return
osdf:// URLs for corresponding
/cvmfs paths, so this likely only works with
Remote data discovery with NDS¶
The LIGO Laboratory supports the Network Data Server (NDS), which enables remote access to observatory data. Version 2 of the NDS protocol supports remote, authenticated access for collaboration members, from anywhere in the world.
For full details, see the NDS2 client documentation.
In contrast to
gwdatafind, which locates files containing a specific data set, NDS2 operates solely on the data channel, and will directly return the data for that channel, regardless of which dataset contains it. This can be extremely valuable when you are not sure which dataset contains a specific channel of interest.
To download data for a specific data channel:
import nds2 conn = nds2.connection("nds.ligo.caltech.edu") print(conn.fetch(1187008866, 1187008898, ["H1:GDS-CALIB_STRAIN"]))