The LRO’s main purpose is to pave the way for future human explorers, and that preparation includes taking extremely high-resolution images of potential landing sites. To do that, the spacecraft will orbit much closer than any of the others—only 31 miles above the surface. Details less than three feet should show up in the images, meaning that 40 years after the Apollo astronauts walked on the moon, we’ll once again see pictures of their equipment and vehicles dotting the lunar landscape. LRO will use a laser-ranger to measure landscape elevations, and will train its instruments on the lunar poles, looking for water and other potentially useful resources. Helping in the search for water is an add-on experiment called LCROSS: An upper-rocket stage will be sent crashing to the surface and scientists will study what flies up from the impact.