 NASA's Bedard Space Flight Center, in cooperation with international partners, manages a fleet of spacecraft monitoring all aspects of the heliosphere. This fleet is called the Sentinels of the Heliosphere. The gray mesh around the Earth that you see is called the Magnetosphere. It's the Earth's magnetic field, pushed back by the solar wind. It's critical for life on Earth because it routes charged particles in the wind around the Earth instead of lending it bombard us head-on. That makes it very important for us to understand. Here's the near Earth fleet. It's monitoring solar activity and orbiting Earth every 92 minutes. Now we are taking a look at the geospatial fleet that orbits deep into and around Magnetosphere. Cluster is a group of four satellites to fly in formation to measure the three-dimensional boundaries of the Magnetosphere as it intersects with the solar wind. Geotail conducts measurements of electrons and ions in the Earth's magnetotail, the Magnetosphere pushed back by the solar wind. Stereo A and B observe the Sun with images and particle detectors, and they fly off the Earth's sun line, providing a three-dimensional view of solar activity. Watch how they use the Moon to set themselves apart at the best possible distance to view the heliosphere. Here we see the L1 fleet orbiting the Lagrange point number one between the Earth and the Sun. L1 is the point between the Earth and the Sun where the gravitational pull is approximately equal in both directions. Spacecraft can orbit this location for continuous coverage of the Sun. Out here there is no magnetosphere, so a good look at the solar wind is possible. Ace measures the composition and characteristics of the solar wind. Wind measures particle flows and fields in the solar wind. Soho is a famous satellite that studies the Sun from its deep core to the outer corona and the solar wind. Here we see the Themis fleet of five satellites that study how magnetospheric instabilities produce the aurora borealis. The heliopause fleet is Voyager 1 and Voyager 2. Voyager 1 has traveled the furthest at 140 astronomical units. That's 140 times further away from the Sun than we are. It takes light almost 19 and a half hours to reach Voyager 1.