The Advanced Small Analyzer for Neutrals (ASAN) on the Chang’E-4 Rover Yutu-2

• Published in: Space science reviews Vol. 216; no. 4
• Main Authors: Wieser, M., Barabash, S., Wang, X.-D., Grigoriev, A., Zhang, A., Wang, C., Wang, W.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.06.2020; Springer Nature B.V; Springer Verlag
• Subjects: Aerospace Technology and Astronautics; Astrophysics and Astroparticles; Atomic properties; Channel multipliers; Charged particles; Conversion; Deflection; Diamond-like carbon; Energetic neutral atoms; Energy resolution; Energy spectra; Field of view; Gallium arsenide; Helium; Hydrogen; Ions; Lunar surface; Moon; Neutral atoms; Oxygen; Physics; Physics and Astronomy; Planetology; Positive ions; Sciences of the Universe; Space Exploration and Astronautics; Space Sciences (including Extraterrestrial Physics; Special Communication; Chang’E-4; Solar wind - regolith interaction; Mass resolving energetic neutral atom analyzer; Lunar surface; Yutu-2; Chang'E-4; regolith interaction; Solar wind
• ISSN: 0038-6308; 1572-9672
• DOI: 10.1007/s11214-020-00691-w

The Advanced Small Analyzer for Neutrals (ASAN) is a compact mass resolving energetic neutral atom analyzer flown on the Yutu-2 rover of the Chinese Chang’E-4 mission to the Moon. ASAN measures energetic neutral atoms in the energy range from 10 eV to 10 keV with typically 30% energy resolution. The field-of-view is a single angular pixel of 37° × 30° pointing at lunar surface. Energetic neutral atoms enter the instrument through a charge particle deflection system and are then ionized on a diamond-like carbon conversion surface. Positive ions from the conversion surface are energy analyzed using an electrostatic analyzer and their velocity is subsequently determined in a time-of-flight section using ceramic channel electron multipliers as detectors. The obtained mass resolution m/ Δ m is about 2, comfortably separating neutral hydrogen, helium, and the oxygen-group (≥16 amu). A full energy spectrum for energetic neutral atoms is obtained in 3 seconds. Switching the charged particle deflection system off, ASAN also directly measures positive ions with similar performance as for energetic neutral atoms. Including electronics the instrument weighs 970 g and consumes 3.4 W.