High Energy X-ray Spectrometer (HEX – ISRO)
The High Energy X-ray/gamma-ray spectrometer made measurements in the 30–200 keV range with a ground resolution of 40 km. HEX measured uranium (U), thorium (Th), lead-210 (210Pb), radon-222 (222Rn) degassing and other radioactive elements on the lunar surface.
Radioactive elements concentrate in specific geological terrains, so HEX's maps helped trace the distribution of KREEP-related materials and volatile transport towards the cold polar regions — one of the first attempts to study lunar volatiles through high-energy X-ray spectroscopy.