ION experiment

This page is a mirror of the ION SADS page available at Besides the information already available on this page, there you can browse the ION QuickLook images.

The ION experiment was designed and built by the Centre d'Etude Spatiale des Rayonnements (CNRS/University of Toulouse, France) and funded by a CNES (French National Space Center) grant. The integration tests were performed jointly with the Space Research Institute, Moscow (IKI).

P.I. to contact for more information

Dr. Jean-Andre Sauvaud

9 avenue du colonel Roche
31028 Toulouse cedex 4, France
Phone: 33 5 61 55 66 76
Facsimile: 33 5 61 55 67 01


The ION experiment flown on the Interball-Aurora mission performs simultaneous ion and electron measurements. Two mass spectrometers looking in opposing directions perpendicular to the satellite spin axis, which points toward the sun, measure ions in the mass and energy ranges 1-32 amu and ~ 0 to 14,000 eV. The ion measurements are complemented by simple electron spectrometers performing measurements in the energy range ~10 eV (or 60 eV) to 20,000 eV.

Ion composition analyzers

The design of the detector heads of the ION-1 and ION-2 mass spectrometers is based on the principle of the Wien filter, where the mass filtering is performed by crossed electric and magnetic fields. The energy over charge (E/Q) selection is made by a cylindrical electrostatic analyzer placed in front of the filter. At each energy step, the electric field in the magnetic analyzer is programmed in order either to scan 2 or 4 ions (H+, He++, He+, O+).

Electron analyzers

Two spectrometers, ION3 and 4, measure electron fluxes. They consist of two cylindrical electrostatic analyzer heads and associated electronics.

Status of the experiment

The ION experiment is working since the end of September 1996. Data are regularly obtained in the cusp, cleft, in the nightside auroral zone showing interesting and newly observed features.

(Click on the picture to view large one)

Fig.1: A cleft pass
Energy-time spectrograms for electrons (top) and hydrogen ions (bottom) on Feb. 24, 1997 between 01:30 and 04:45 UT. Counts are color coded. The satellite altitude H in RE, the invariant latitude L0 in degrees, the magnetic local time MLT in hours, and the longitude: LONG in degrees, are given at the bottom of the Figure.

(Click on the picture to view large one)

Fig. 2: Ion gaps
Energy time spectrograms of hydrogen ions showing ion gaps of different origin (very large drift time, no source...) on Feb. 5, 1997.

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Fig.3: Substorm related injections
Substorm related ion injections at the polar cap boundary (auroral surge) and inside the inner magnetosphere on December 22, 1996 starting at ~16:40 UT.