Laser Altimeter
An instrument that measures surface elevation by timing the return of laser pulses reflected from a planet’s surface. MESSENGER’s altimeter was key to mapping Mercury’s topography.
Source: nasa.gov
APODs including "Laser Altimeter"
The Spiral North Pole of Mars
06/07/2025
Why is there a spiral around the North Pole of Mars? Each winter this pole develops a new outer layer about one meter thick composed of carbon dioxide frozen out of the thin Martian atmosphere. This fresh layer is deposited on a water-ice layer that exists year round. Strong winds blow down from above the cap's center and swirl due to the spin of the red planet -- contributing to Planum Boreum's spiral structure. The featured image is a perspective mosaic generated in 2017 from numerous images taken by ESA's Mars Express and elevations extracted from the laser altimeter aboard NASA's Mars Global Surveyor mission.