Lunar Sounder Experiment

Description

The Apollo Lunar Sounder Experiment (ALSE) was designed to (1) map the subsurface electrical conductivity structure to infer geological structure, (2) make surface profiles to determine lunar topographic variations, (3) produce surface imaging, and (4) measure galactic electromagnetic radiation in the lunar environment. The ALSE was a three-wavelength synthetic aperture radar (SAR) operating at 60 m, 20 m, and 2 m (5, 15, and 150 MHz). The radar data were recorded on 70-mm photographic film in a conventional SAR format, and returned to earth for processing. The HF-1 system (5 MHz) was capable of the deepest exploration. The HF-2 system (15 MHz) was operated simultaneously with the HF-1 system to provide partial overlap in the depth of exploration, trading off for improved resolution. The VHF system (150 MHz) was designed for shallow sounding and for surface imaging. All three frequencies were capable of surface profiling. Separate transmit/receive antenna systems were provided for the HF and VHF ranges. The returned data were optically processed and provided good profiles of the lunar surface/subsurface.