Five days before Superstorm Sandy hit the East Coast, weather forecasters predicted its infamous "left hook" -- the sharp turn that drove it straight into the New Jersey shore. That early warning was mostly due to polar-orbiting satellites, the high-tech flecks in the sky that rotate just 600 miles above the Earth's surface. Circling the planet on a north-south orbit, the satellites provide forecasters with high-resolution images and detailed data that their geostationary counterparts miss from a 20,000-mile-high perch. But soon, some of that data could disappear.