Mobile Outpost

Two antennas send information to Earth from a high point on the landscape atop NASA's Mars Exploration Rover Spirit on martian sol 210 (Aug. 4, 2004). The tall antenna on the left sends UHF signals (like some, but not all, signals used for television broadcasts) to orbiting spacecraft. Orbiters such as the Mars Odyssey spacecraft relay the signals to Earth. The round, high-gain antenna on the right sends and receives X-band microwave signals (like the ones used in alarm system motion detectors and police radar guns) directly to Earth. Mission planners at NASA's Jet Propulsion Laboratory send commands directly to the rover via the high-gain antenna. In front of the rover, at the top of the ridge on the "West Spur" of the "Columbia Hills" overlooking the surrounding plain, is the rock outcrop dubbed "Longhorn." On the horizon is the rim of the 165-mile-wide (103-mile-wide) Gusev Crater, where Spirit landed Jan. 4, 2004. This image was taken with Spirit's navigation camera.

Image credit: NASA/JPL