Chang’e 4 (ASAN) 

In the end of December 2018 the Chinese spacecraft Chang’e 4 was sent to the moon. The spacecraft carries a lander and a mobile robot and landed on the far side of the moon 3 January 2019. IRF in Kiruna participates with the Advanced Small Analyzer for Neutrals instrument (ASAN).

Advanced Small Analyzer for Neutrals, ASAN. Photo: IRF

The instrument is mounted on the mobile robot, 60 centimetres above the ground, where it will investigate the interaction between the solar wind and the lunar surface. This will be done by measuring energetic neutral atoms and ions coming from the surface of the moon. The lander and the mobile robot will study their environment for at least three months.

Ongoing research

Scientificly, the measurements with ASAN are a continuation of the observations made with an IRF-built instrument on board the Indian lunar probe Chandrayaan-1 in 2008-2009.

The instrument on Chandrayaan-1 investigated how the particles in the solar wind interact with the moon’s surface. It was then discovered that a surprisingly large number of the solar wind’s ions are reflected from the surface.

It was also possible to see how the solar wind behaves around the magnetized areas found on the lunar surface. Chandrayaan-1 made its observations from a 100-200-kilometre high orbit. With ASAN, the measurements will be made just over half a metre from the ground. The researchers hope to learn many new things about how the solar wind interacts with the surface.

Contact person:
Dr Martin Wieser, IRF Kiruna, tel. + 46-980-79198,

Created by Annelie Klint Nilsson at

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