Thin-Sat Payload for Measuring Spacecraft Charge and Local Ion Number Density

Testing a single polarity electrospray thruster in low earth orbit (LEO) presents unique challenges. Due to the thruster’s emission of a single polarity ion, it is likely that the spacecraft will develop a charge with respect to the expelled particles. To determine the magnitude of this charge and whether it will naturally dissipate, a spacecraft potentiometer is required. In addition, a Langmuir probe instrument is necessary to measure the local plasma properties in the orbit to which the spacecraft is launched so that spacecraft potential can be compared with local plasma properties. An instrument capable of performing both measurements was designed and is planned to be tested onboard a small 0.5U Thin-Sat. The satellite bus is being provided by NearSpace Launch (NSL) and will be launched as a part of a six-satellite constellation sometime in early 2026. A successful mission will validate the instrument for future in-space electric propulsion experiments and missions.