ELENA (Emitted Low-Energy Neutral Atoms)

ELENA (Emitted Low-Energy Neutral Atoms) is a neutral particle camera that investigates neutral gases escaping from the surface of Mercury, their dynamics and the processes responsible for such a population. ELENA has a field of view of 4.5ºx76º, directed towards the surface of Mercury (nadir) with angular resolution in the wide direction of 4.5º x 4.5º. The second dimension of the map will be provided by the movement of the spacecraft.
ELENA measures energetic neutrals between 20 eV – 5 keV. The ELENA measurements will allow mapping neutral particle released from the surface after ion back scattering and ion sputtering, as well as charge-exchange ENA generated from exosphere interaction with the ion close to the surface.

ELENA Flight Model

ELENA technological highlights

The basic concept of ELENA is based on direct particle detection removing the background signal and leaving the Energetic Neutral Atoms (ENA) untouched, so that the directionality is preserved. The composite radiation made by neutral atoms, ions, and light impinges onto the ELENA sensor entrance. A powered wired grid system at the entrance minimizes the ion and electron background radiation. After that a nanometric grid filter the UV radiation. An internal ion deflector is a stack of particle cross-track grids which introduce a transversal E-field able to filter out the bulk of the charged particles of both polarities. The unit defines intensity and direction of the incoming particles.

SCU (System Control Unit) is inside the ELENA box and manage all the interfaces of SERENA sensors with the spacecraft: TC and TM, power distribution and emergency signals.