The Langmuir Probe Instrument on Board the Rashid-1 Rover of the Emirates Lunar Mission

The Rashid-1 rover, which was part of the Emirates Lunar Mission (ELM) program, was a small rover aimed to be operated for one lunar day on the lunar surface. As part of its scientific instrumentation, Rashid-1 carried a Langmuir probe experiment (LNG) in order to provide the first extensive, high-resolution in situ measurements of the bulk parameters of the lunar dayside thermal plasma at different altitudes above the lunar surface. The LNG was comprised of four probes, mounted at different locations and heights above the lunar surface on the Rashid-1 rover. This way, the LNG was intended to derive an altitude profile of the two plasma parameters electron density and electron temperature above the lunar surface. The design of the instrument and a description of the data analysis technique, calibration, and validation are provided in this paper. Due to the short separation between the probes and the rover body (in terms of Debye length), the measurements of the LNG were expected to be influenced by the presence of the rover and its sheath. This was addressed through numerical modeling, which is described and preliminary results are presented. Unfortunately, the landing in the Atlas crater of the lunar lander carrying Rashid-1 to the surface was not successful – however, this description of the instrument design and the data analysis techniques are still useful for future explorations of the lunar plasma environment.