First, where will your picosatellite go? It’s nearly a given that your picosatellite will go to low earth orbit (LEO), a broad band ranging from about 150km up to perhaps 600km. This is the region that also has many science satellites and the International Space Station (ISS). It is in and below the ionosphere, the very, very thin part of the atmosphere that also coincides with much of the Earth’s magnetic field.

The Earth’s magnetic field shields us from the Sun’s most fierce activity. High-energy particles, flare emissions, and coronal mass ejections (CMEs; basically blobs of Sun-stuff) get shunted by the magnetic field before they can reach ground. Where the magnetic field lines dip near the poles, this energy expresses itself as the aurora (see Figure 1-2).