On January 14, 2008, MESSENGER's Mercury Laser Altimeter (MLA) became the
first instrument to measure the distance between a spacecraft and the
surface of Mercury. MLA operates by first firing a brief laser pulse at
the surface. It then measures the time for the pulse to reach the surface
and return to the spacecraft, thereby providing a precise distance.
This figure shows the distance, or range, from the MESSENGER spacecraft to
the surface of Mercury as measured by MLA during the flyby of Mercury. The
instrument acquired the surface at a slant range of about 600 kilometers
(about 370 miles) and tracked the surface through closest approach near
200 kilometers (about 125 miles) and out to a distance of about 1500
kilometers (about 930 miles). During the Mercury encounter, the instrument
met or exceeded all performance specifications. The MESSENGER team is
continuing to process the MLA data, and the final results should enable
distances to be measured to better than a meter, allowing the profiles of
craters and other features to be measured.
The vertical exaggeration in the figure is about 5:1. The MLA was designed
and built at the NASA Goddard Space Flight Center.
These images are from MESSENGER, a NASA Discovery mission to conduct the
first orbital study of the innermost planet, Mercury. For information
regarding the use of images, see the MESSENGER image use policy.