one used on the lunar surface during Apollo 11. ALSEP The Apollo Lunar Surface Experiments Package, or ALSEP, was a suite of scientific instruments designed to be emplaced on the lunar surface by the Apollo astronauts, and thereafter operate autonomously, sending data to Earth. Development of the ALSEP was part of NASA's response to some scientists who opposed the crewed lunar landing program (they felt that robotic craft could explore the Moon more cheaply) by demonstrating that some tasks, such as deployment of the ALSEP, required humans. In 1966, a contract to design and build the ALSEPs was awarded to the Bendix Corporation Due to the limited time the Apollo 11 crew would have on the lunar surface, a smaller suite of experiments was flown, known as the Early Apollo Surface Experiment Package (EASEP). Apollo 12 was the first mission to carry an ALSEP; one would be flown on each of the subsequent lunar landing missions, though the components that were included would vary. Apollo 12's ALSEP was to be deployed at least away from the LM to protect the instruments from the debris that would be generated when the ascent stage of the LM took off to return the astronauts to lunar orbit. Apollo 12's ALSEP included a Lunar Surface Magnetometer (LSM), to measure the magnetic field at the Moon's surface, a Lunar Atmosphere Detector (LAD, also known as the Cold Cathode Ion Gauge Experiment), intended to measure the density and temperature of the thin lunar atmosphere and how it varies, a Lunar Ionosphere Detector (LID, also known as the Charged Particle Lunar Environment Experiment, or CPLEE), intended to study the charged particles in the lunar atmosphere, and the Solar Wind Spectrometer, to measure the strength and direction of the solar wind at the Moon's surface—the free-standing Solar Wind Composition Experiment, to measure what makes up the solar wind, would be deployed and then brought back to Earth by the astronauts. A Dust Detector was used to measure the accumulation of lunar dust on the equipment. Apollo 12's Passive Seismic Experiment (PSE), a seismometer, would measure moonquakes and other movements in the Moon's crust, and would be calibrated by the nearby planned impact of the ascent stage of Apollo 12's LM, an object of known mass and velocity hitting the Moon at a known location, and projected to be equivalent to the explosive force of one ton of TNT.