Radar signals are beamed at the Earth from a transmitter in Endeavour's cargo bay. Receiving antennas in the shuttle's cargo bay and at the end of the boom enable the astronauts to receive and record the signals as they bounce off the Earth. After the flight, experts plan to convert the stereo recordings into a three-dimensional map of all of the terrain south of Hudson Bay and north of Cape Hope, or least 70 percent of the Earth's major land mass. The technique should produce topographic maps with much more detail and twice the accuracy of current global maps, NASA said. By late Sunday, the shuttle astronauts had scanned more than 17 million square miles of the Earth's surface at least once, or 30 percent of the mission's goal.
Scientists hope to scan all of their targets at least twice.
As of Sunday, a little over 6 percent had received a second scan. Caro said it was too early to speculate on what regions of the Earth would go unmapped if the mapping is curtailed. Of course, our intent is to map the entire Earth. As of now, I'm very happy because we are getting everything we want. If the mapping must be halted early, it would be the second curtailment.