The ALSE (Apollo Lunar Sounder Experiment) (also known as Scientific Experiment S-209, according to NASA designations) was a ground-penetrating radar (subsurface sounder) experiment that flew on the Apollo 17 mission.
ALSE (Apollo Lunar Sounder Experiment) (juga dikenal sebagai Scientific Experiment S-209, menurut sebutan NASA) adalah sebuah radar percobaan tembus tanah (bawah permukaan sounder) yang terbang pada misi Apollo 17.