We have met the aliens, and they are us.

NASA Space Shuttle Radar Reflector
"This corner reflector is temporarily placed in Death Valley to obtain precise measurements of the radar signal from the Shuttle Radar Topography Mission."

Mark Holloway of Beatty, Nevada, photographed this corner reflector in Death Valley, California. More information about the reflector and the Shuttle Radar Topography Mission is on display in the Furnace Creek Visitor Center and online at www2.jpl.nasa.gov/srtm/mission.htm.