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Illustration of Lagrange Points
Original Windows graphic, by Sarah Joseph

Lagrange Points

We could learn a lot about the solar wind if we could put satellite in one place in space. Changes in the solar wind could be measured easily. If the satellite is between Earth and the Sun, it could be an early warning system. It would let us know about any changes in the solar wind before they reached the Earth.

The problem with putting a satellite in one place is that it is impossible. To resist gravity, a satellite has to be moving. Nearly as helpful would be if the satellite could orbit the Sun in a one-year orbit, to match the Earth.

There are five places where this can happen. They are called Lagrangian points. These points are places where a satellite would have the same orbit time as the Earth. L1 is just inside Earth's orbit, the best place for an early warning system.

The ACE and SOHO spacecraft are both at L1. This point is about 1.5 million km from the Earth.

Last modified June 26, 2001 by Jennifer Bergman.

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF