LP3 -- High-performance Langmuir probe cubesat unit

The Langmuir probe (LP) is a conceptually simple instrument for in situ plasma measurements, well suited to the relatively dense plasma of the ionospheres around the Earth and other solar system bodies with ionospheres.

To understand the physical processes in these environments it is essential to have several measurement points: to see why, consider what state meteorology would be in if there was only one weather station on Earth.

Multi-spacecraft missions are therefore important, but costs obviously increase.Cubesats, small satellites build up from cubic units 10x10x10cm in size (1U), have in the last decades emerged as a cheap means of reaching the terrestrial ionosphere.

The small size of demands miniaturisation of all systems, and to keep costs low, commercial of the shelf (COTS) components are often used, and the design practices and guidelines of full-size space missions (e.g. the ECSS standard) are not always adhered to.

While this has lowered the entry threshold to space, most cubesat missions are "technology demonstrators" with short lifetime.One of the goals of this project is to develop and qualify a LP instrument, called LP3, fitting into one single 1U cubesat unit, including sensors.

While the LP3 unit will be possible to fly on a traditional COTS-based cubesat we aim for a design which can relatively easily be adapted for ECSS and therefore be used on higher profile scientific missions including ionospheres around other planets. Fitting all parts, including sensors, into one unit means interfaces to the spacecraft are minimized.

Such simplifications are a big help in mission design.The LP3 will also improve on existing LP measurement technology.

We will use three sensors, one planar probe for a robust ion density measurement and two cylinder probes for electron density and temperature and spacecraft potential. Comparing the ion and electron measurements makes it possible to check data quality and establish error limits.

The cylinder probes are a new design with materials shown to be insensitive to some of the problems encountered with hitherto used coatings and a foldable boom to distance the probes from the perturpations of the spacecraft.