SOLAR sails could relieve traffic congestion in the skies above Earth.
For a satellite to hover above a point on Earth’s surface, its orbit must encircle the equator. Such geostationary orbits allow uninterrupted communication or imaging, but room for new satellites is beginning to run out. “It’s a finite natural resource, a unique circle around Earth,” says Colin McInnes of the University of Strathclyde in Glasgow, UK.
A satellite orbiting slightly north or south of the equator would drift relative to the ground. Now McInnes and colleague Shahid Baig have shown how to counteract that drift by fitting satellites with…
