NASA Logo, National Aeronautics and Space Administration
NASA Space Science Data Coordinated Archive Header

Negative Ions at the Lunar Surface (NILS)


Mission Name: Chang'e 6


The Negative Ions at the Lunar Surface (NILS) experiment is a mass spectrometer with the primary objective of measuring the flux of negative ions emitted from the lunar surface as a result of the interaction with the solar wind. The scientific goal is study the role of negative ions in space-surface interactions and in the lunar exosphere. The experiment is a collaboration between the Swedish Institute for Space Physics and the Chinese Space Agency.

Mounted on the lander, the NILS mass spectrometer system uses an electrostatic analyser and a time-of-flight cell to measure the energy per charge and the mass per charge of incident ions. NILS instantaneously records negative ions and electrons from a single direction. Two cylindrical electrodes act as a deflection system to allow for a one-dimensional 160 degree scanning of the viewing direction. An electron suppression system directly behind the deflection system separates negative ions and electrons before they reach the first-order focusing cylindrical electrostatic analyser.

Ions are accelerated by a -400 V potential before entering the time-of-flight cell. Particles reflect off a single crystal tungsten surface, triggering the start signal via a channel electron multiplier. The stop signal is generated after the particle reaches a stop surface and generaters a secondary electron detected by another electron multiplier. This gives the time of flight, combined with the electrostatic analyzer energy setting the mass per charge of the particle can be determined. The system allows detection of H- and sputtered negative ions in the sub-keV range.

Alternate Names

  • Change6/NegativeIonsattheLunarSurface(NILS)
  • NILS

Funding Agency

  • China National Space Administration (Peoples Republic of China)


  • Planetary Science: Fields and Particles

Additional Information

Questions and comments about this experiment can be directed to: Dr. David R. Williams



NameRoleOriginal AffiliationE-mail
[] NASA Logo -