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The Multi-needle Langmuir Probe Instrument for QB50 Mission: Case Studies of Ex-Alta 1 and Hoopoe Satellites


The QB50 mission is a satellite constellation designed to carry out measurements at between 200–380 km altitude in the ionosphere. The multi-needle Langmuir probe (m-NLP) instrument has been mounted on board eleven QB50 satellites in order to characterize ambient plasma. The distinct feature of this instrument is its capability of measuring the plasma density at high spatial resolution without the need to know the electron temperature or the spacecraft potential. While the instrument has been deployed on many sounding rockets, the QB50 satellites offer the opportunity to demonstrate the operation of the instrument in low-earth orbit (LEO). This paper provides a brief review of the m-NLP instrument specifically designed for the QB50 mission and the case studies of the instrument’s performance on board the Ex-Alta 1 and Hoopoe satellites. The system has also been functionally verified in a plasma chamber at the European Space Research and Technology Center (ESTEC). Although the QB50 mission’s scientific goals have not been reached yet and some uncertainties still remain, there are some optimistic in-orbit preliminary results which could be helpful for the system improvement in future campaigns. Particularly, the electron emitter as part of the m-NLP science unit has demonstrated its capability in the plasma chamber and in orbit to mitigate spacecraft charging effects.

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This research has received financial support from Research Council of Norway project 208006, 230996 and ESA PRODEX project 4200090335. The research leading to these results has also received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement 284427. The work is also a part of the 4DSpace initiative at the University of Oslo. Ex-Alta-1 was carried out with the financial support of donors, two crowd-sourcing campaigns, from the Canadian Space Agency, and from the Canadian Natural Sciences and Engineering Research Council (NSERC) through a Discovery Grant to Ian R. Mann.

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Correspondence to H. Hoang.

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Multi-Point Measurements of the Thermosphere with the QB50 Mission

Edited by David Miles, Robert Wicks and James Burch

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Hoang, H., Røed, K., Bekkeng, T.A. et al. The Multi-needle Langmuir Probe Instrument for QB50 Mission: Case Studies of Ex-Alta 1 and Hoopoe Satellites. Space Sci Rev 215, 21 (2019).

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  • QB50
  • Langmuir probe
  • Electron density
  • Spacecraft charging