The Fast Auroral SnapshoT Explorer was launched into orbit on August 21, 1996. The instruments aboard FAST measure charged particles which enter Earth's upper atmosphere; large waves of these particles from the sun begin to glow once inside Earth's atmoshpere causing a spectacular light show known as the Aurora Borealis or Northern Lights. NEW! Visit the SEGway International Heliospheric Year(IHY) website with Sun-Earth connection activities, talks, and data for use around the world.