Chang'e-3 APXS delivers its first surface analysis

Active Particle-induced X-ray Spectrometer (APXS) components on the Chang'e-3 "Yutu" lunar rover [Xinhua/CNSA/CLEP/IHEP/CAS].

The Active Particle-induced X-ray Spectrometer (APXS), on the Yutu rover delivered to the lunar surface by the Chang’e-3 lunar lander, on December 25 sent back its first X-ray fluorescence spectrum of the lunar regolith around the landing site in northwest Mare Imbrium.

The announcement was made by the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences (CAS), December 30.

Initial analysis indicates a marked presence of eight major rock-forming elements: magnesium, aluminum, silicon, potassium, calcium, titanium, chromium and iron (Mg, Al, Si, K, Ca, Ti, Cr and Fe) and at least three minor elements, strontium, yttrium and zirconium (Sr, Y and Zr) identified in this spectrum. 

First X-ray florescent spectrum of the lunar surface at the Chang'e-3 Mare Imbrium landing site (click to enlarge) [IHEP/CAS].

The energy resolution of APXS is estimated at roughly 135 at 5.9keV (thousand electron volts), demonstrating the small instrument is among the best X-ray spectrometers yet deployed in direct planetary exploration.

APXS was initially powered up on December 23, and in-flight calibration, establishing a baseline by analyzing a common basalt rock sample of known composition mounted on the rover, was completed over five minutes, preparing a stable performance on the lunar surface. After two terrestrial days APXS was successfully deployed to within two to three centimeters over the regolith of Mare Imbrium on the robotic arm of Yutu and began its designed operation. 

Complimenting its X-ray spectrometry, the APXS instrument measured returned X-ray count rate at various distances.

APXS components (sensor head, radioactive heat unit (RHU) and inflight baseline calibration target [IHEP/CAS].

China's Institute of High Energy Physics (IHEP) developed APXS in collaboration with the China Academy of Science Purple Mountain Observatory (PMO). Before the on-going Chang'e-3 mission two X-ray Spectrometers developed by IHEP, flown on Chang’e-1 (2007) and Chang’e-2 (2010).