Measuring Height

Just how bumpy are those lunar surfaces? JAXA (and armchair moon enthusiasts) can get a feel for the moon thanks to height profiles, like this yellow cross-section diagram of range data passing over the moon's Orientale Basin.

Orbiting at 100 kilometers above the lunar surface, KAYUGA transmits laser pulses to the moon with its laser altimeter (LALT). By measuring the timing for returned signals, it can calculate the distance between the moon's surface and the orbiter and hence, shape of the surface. The earthly landmarks Mt. Fuji and the Japan Trench are shown for comparison on the vertical axis.

This topographic map shows the Theophilus crater, located in the west side of the Mare Nectaris. The data reveals the crater's impressive features: a diameter of 100 kilometers, a rim 2,000 meters above the surface, and a depth of approximately 5,000 meters from the rim. That's about three times as deep as the Grand Canyon.

Image courtesy of JAXA/SELENE Background image NASA