Speaker
Mr
Denis Payan
(CNES)
Description
Electrostatic discharges (ESD) are a major risk of failures in orbit. From temporary outage to power loss with secondary arcing, the panel of possible degradation is very wide. The tribute already paid by the agencies, insurance or operator is very high and expressed in millions euros.
Coming from the sun, particles hit all the spacecraft on every orbit, building up very negative absolute potential. Then difference in materials, temperature, lightening allows to create voltage gradient at the origin of ESD.
Unfortunately, the number of spacecraft with particles measurements onboard is very low and most of time, it is for scientific applications. Thus Satellites undergo charging incoming fluxes from the sun after their trip along earth magnetic field lines, increasing their energy without any precise idea of the real effect on the spacecraft itself. Thus every spacecraft should have onboard that kind of sensor.
At the exact time of an anomaly, we would perfectly know the absolute voltage of the spacecraft and the full history of the particles received, making failures analyse possible and precise. As positive particles are accelerated by the negative voltage of the spacecraft body, the positive spectrum measured gives also the absolute voltage. On the opposite side, the negative head gives us the incoming charging fluxes.
Today for failure analyse, spectrums are extrapolated (computed some times) from higher energy measurements (when they are available), generally on other orbit position and other altitude. In other words, attribute a failure to an ESD on a specific spacecraft cannot be made with a good reliability.
In addition, most of environment data available on the web are distributed by NOAA or LANL, the energy range started at 40kev which is already too high for surface charging concern. Unfortunately those low energy spectrums are no more available (since 2008, the first of January) due to ITAR restriction. This lack of data may be the premise of what awaits us more broadly. Though following each solar eruption remains very important even in the very beginning of the spacecraft life for the launch.
Making those results available would also interest the whole scientific community. As the measurements are not available or very rare, we need to provide ours. For example, the simulation of the dynamic of the magnetosphere, especially at low energy needs a great number of measurement points at different position and orbit. The starting one could be on JASON3.
And finally at project level, it would also allow us to know if the design rules imposed for EMC/ESD reasons are valuable and mandatory or could be relaxed.
Based on dozens of years of experience of IRAP (Institut de Recherche en Astronomie et Planétologie) with Giotto, Interball, Cluster or Stereo, the specific head of CARMEN is dedicated to low energy plasma measurement between 0 and 30keV. Its principle is a mass spectrometer where a biasing voltage is sweeped between two hemispheres. Particles engulfed in it and are thus counted and specific electronic provide data to CARMEN.
Impact on the JASON3 spacecraft is minimised due to the principle of CARMEN hydra. Screwed on a wall outside from the spacecraft only one harness is connected to Carmen and there is no electrical connection to the spacecraft. As visibility is possible from every side, implementation area is large and constraint very low. Mechanical interaction is resumed to 4 screws and thermal regulation is fully passive.
Primary author
Mr
Denis Payan
(CNES)
