MESSENGER Laser Altimeter (video) NASA/Goddard Space Flight Center Share Print E-Mail Loading video... Caption MESSENGER's Mercury Laser Altimeter sends out laser pulses that hit the ground and return to the instrument. The amount of light that returns for each pulse gives the reflectance at that point on the surface. The amount of time it takes the pulse to make its trip indicates how far away that point on the surface is, allowing the topography to be mapped. Credit NASA/Goddard Space Flight Center Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.