S69-39587 (20 July 1969) --- Dr. Garry Latham (left) with the Lamont Geological Observatory, studies seismometer tracings in the Mission Control Center's (MCC) ALSEP control room. The electronic data was coming from the Passive Seismic Experiments Package (PSEP) which the Apollo 11 astronauts had just deployed on the surface of the moon. Dr. Lamont is the principal investigator for the PSEP, a component of the Early Apollo Scientific Experiments Package (EASEP). PSEP uses three long-period seismometers and one short-period vertical seismometer for measuring meteoroid impacts and moonquakes. Such data will be useful in determining the interior structure of the moon; for example, does the moon have a core and mantle like Earth? Here, the flapping of the PSEP's solar panels is picked up and registered as a tracing. The PSEP was sensitive enough to pick up the footsteps of astronauts Neil A. Armstrong and Edwin E. Aldrin Jr., as they walked on the moon.