The objective of this activity is to develop an Electric Propulsion Diagnostic Package (EPDP) to:

• Act diagnostic measurements on the plume of the electric thruster of HET and HEMPT type using Langmuir probes and Retarding Potential Analysers.

• Measure the sputtering and back sputtering on the spacecraft using quartz crystal microbalances (QCM).

 

So far a growing number of satellites is using electric propulsion systems for orbit raising and/or station keeping to save propellant mass with respect to chemical propulsion systems. Therefore, understanding the plasma plume of the electric thrusters and its interference with the spacecraft surfaces is of high importance. To account for this effect, extensive on ground experimental campaigns are conducted assessing the plasma plume of different thrusters. However, it is still under debate, how the plasma plume will change under space conditions. Different parameters like the background pressure of neutral atoms, the space plasma and the spacecraft geometry could influence the plasma.

 

Thus, the project aims to a detailed design, manufacturing and the test of the EPDP system elements to measure the s/c relevant plasma plume parameters. A complete EM standard system, together with structural thermal models and components shall be manufactured and tested in ground based test facilities as necessary. Another outcome of such a diagnostic package on-board of an EP satellite platform would be a better understanding of the thruster performance in space in comparison to the ground based tests, which would lead to a design enhancement of the EP subsystems. Furthermore, the measurements on the s/c plasma environment can help validate the S/C SPIS model and studying its charging phenomena.

 

The plasma sensor package shall have the opportunity for an in orbit verification. This enables the very special opportunity of investigation of the two different electric propulsion systems HET and HEMPT. The package will contain a Retarding Potential Analyser (RPA) and a Langmuir Probe (LP) to measure the plasma potential, electron temperature, ion energy and ion current density in the backflow region of the electric thrusters. The RPA and the LP will be designed to measure backscattered ions. This data provides comprehensive information about the plasma at the measurement point. Furthermore, the package will contain an erosion sensor, which will measure the silver erosion from the thruster plasma at the solar panel.

 

Finally, despite the target TRL level being 6, the project should result in a design of the EPDP, which can be adapted for higher TRL quickly and easily.