Tutorial Step 1: Download LIGO Data

Find times with available data

Data for the LIGO detectors is only available during times when the detectors were operating under normal conditions. Times when LIGO data are publicly available are labeled with the DATA flag (i.e. DATA is available at this time). Before trying to download any LIGO data, you may want to get an idea of which times LIGO data is available. The LOSC Timelines provide a convienient, graphical tool for discovering times when LIGO was collecting data. You can find a list of available Timelines by clicking the Timelines link in the menu bar on the left.

Let's start by looking at the DATA Timeline for H1 during LIGO's fifth science run (S5): S5 H1_DATA Timeline. Clicking this link, you should see plots similar to this

Here are some notes to help understand the LOSC Timelines:

  • The label on the far left indicates which instrument is represented in the plot. In this example, H1 corresponds to the "Hanford One" detector.
  • The red curve shows what fraction of time data is available, or the duty cycle, in each time bin, so the y-axis goes from 0 to 100%.
  • This data set spans the LIGO 5th Science Run (S5, 2005-2008).
  • Plot properties can be adjusted by using the buttons at the top of the page, or clicking on a section of the plot.

Query to Find Data Files

Now that we've got some idea when data is available, let's get the actual data files. We'll try to find data for the first month of S5, from November 1 to December 1 of 2005. We can query the S5 archive for the data we want. You can navigate to the S5 archive by following the "Data & Catalogs" link in the menu bar at left. Here, you will find a web form to query for data files.

  • Navigate to the S5 archive or the S6 archive.
  • Use the radio buttons to select "H1".
  • In the web form, enter the dates 2005-11-01 and 2005-12-01.
  • Then, click the continue button.
This will query the database for data files between the entered dates. You should see a list that looks like this:

Each line of the table corresponds to a data file (or tile) covering 4096 seconds of calendar time. A given instrument may be up or down for any fraction of that time, and the far right column shows what fraction of the 4096 seconds containing science mode data.

Let's download one data file, which we'll use for the rest of this tutorial. Since we want a file with mostly Science Mode data, let's download the file that starts at GPS time 815411200.

To download the file, just click the link in the column under the heading "HDF5". After the download completes, create a directory on your computer where you want to store the file, and move the file to its new home.

Use Timeline to Download Data Files

We can also use Timeline to find and download data. As an example, we'll download the same 4096 s of data that starts at GPS 815411200, which is on November 7, 2005. This is very close to the beginning of the S5 run:
  • Navigate to the S5 H1_DATA Timeline
  • Click on the plot in the first month of the run, November 2005. You can use the buttons near the top of the page to zoom out if you make a mistake.
  • Click the link that says "Download this data", and then the "H1" link under "Get Strain Data".
  • This should give you a list of data files similar to the last step. You can choose the file you want from the list. Click HDF5 to download the data.

Scripting downloads

Notice that the data files are accessible through links with predictable names, so it is also possible to write scripts to download multiple data files.

What's next?

Now that you have a LIGO data file downloaded to your computer, you can use Python packages to see what is in the file and make some plots.