How to Work with Segments

GW Observatory data are not always available. In addition, there are times when data may be available, but of poor quality. For these reasons, most work with gravitational-wave data begins with a "segment list", specifying the times of data to be analyzed.

Types of segments

GW Observatory data contain a variety of segment types, but there are generally three types:

• The segments that include DATA (e.g. H1_DATA) indicate strain availability.
• Segments denoted with CAT indicate problems with the data. There are several CAT severities indicated by an integer (e.g. H1_CAT1, H1_CAT2, H1_CAT3; CAT1 being the worst).
• Hardware injections are marked with HW_INJ. For more information, see the Data Quality Segments heading on the O3b run documentation.

Finding Segment Lists with Timeline

1. Pick a dataset and the page will reload to adjust the GPS times for the whole duration of the dataset.

   You can adjust the GPS interval you are interested in by changing the boxes.

   

2. In the strain file section, you can download strain files for the run and GPS interval defined in the previous step.

   Click the buttons with the corresponding detector to download from the archive page.

   Note: Strain links are not available for event segments. You can find strain files for events on the Event Portal page for each event.

   

3. To visualize the timeline segments, select the checkboxes for the segments you want to visualize and click on the Display button.

   A new page will open in a new tab with the segments on an interactive plot.

   

4. To retrieve the segments in a JSON format, click on the JSON tab and then click on the segment of interest. The list of segments will open in a new tab.

   You can inspect the segments on the "segments" key.

   The button All Timelines will show all the timelines available for the dataset as a single JSON list.

   Learn what other data products you can find in JSON format in our API Documentation page.

   

5. To retrieve the segments in a ASCII format, click on the ASCII tab and then click on the segment of interest. The list of segments will open in a new tab.

   

   Each line of the output represents a segment that passed the segment criteria.

   Each line consists of 3 numbers:

   1. the starting GPS time of the segment
   2. the end GPS time of the segment
   3. the duration of the segment in seconds

   For example:

       844605900 844606294 394
       844606594 844606649 55
       844606759 844607779 1020
   

6. Use the links on the right sidebar for quick access to common segment queries.