A new device for the mitigation and control of negative spacecraft charging phenomena has been developed at Thales Alenia Space in Italy. The instrument is based on a very low weight and power consuming cathode, emitting electrons in a diode configuration. The emitting units can be moderately biased with respect to the spacecraft ground in order to guarantee the net current exchange with the environmental plasma and assure the discharge of the spacecraft under negatively charged condition.
The prevention/alleviation of the S/C surface charging is an effective approach to drastically reduce risky situations impacting the S/C health. The charging status of a S/C can be influenced basically with two approaches:
- Passive techniques: By proper and careful selection of surface materials and geometries and by implementing suitable grounding philosophies,
- Active techniques: By providing a suitable controlled current source that can compensate for the environmental charged particles (namely electrons) and thus keep the S/C potential close to zero.
The Active Charging Compensator System (ACCS) is an instrument, proposed and developed by TAS-I, dedicated to the active control of the S/C Charging level (preventing/alleviating the build-up of a surface charging retained dangerous for the S/C safe operation), by a controlled emission of electrons generated and accelerated through a suitable electron generation device.
The ACCS can be considered an actively conditioned device, but its operation, once the cathode has been activated and the device switched on, acts in a passive way ( as the electrons emission can be considered also self-controlled).
The ACCS is suitable for reducing or preventing negative absolute charging of the overall S/C main structure (absolute charging prevention ). Furthermore, a S/C part – charged with respect to another S/C part - can be protected as well (differential charging prevention), provided that the eventual potential build-up around the S/C does not trap the emitted electrons.
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