We present a portable electronic system for real-time monitoring of particle fallout, targeting avionics and space missions. Particulate contamination can be detrimental to spacecrafts in several ways including failure of precision mechanisms, light absorption or scattering on mirrors and others. It is therefore important to control, measure and verify the particulate contamination levels on spacecraft systems during fabrication of the flight hardware, assembling of the payload and in the launch phase, as well as during long missions.

The proposed prototype leverages an integrated electronic CMOS chip that counts in real-time dust particles down to 1 micron diameter. The chip tracks with a millisecond timescale the capacitance between two electrodes, that is affected by the arrival of dust particles, ensuring single event monitoring and a dynamic range of about ten million dust particles over a sensitive area of 1.15 mm2. The system features a low-power microcontroller for setting the chip operation, an analog-to-digital converter for the acquisition of the particle fallout events, a Bluetooth transmitter for data read-out and all the other hardware and software functionalities that ensure a completely autonomous operation. The overall current consumption of the prototype is 30 mA, that can be provided with a USB charger or a standalone battery. The footprint of the instrument is 50 mm x 42 mm x 20 mm, therefore it can be placed in close proximity to the object whose cleanliness needs to be monitored.

Small area occupation, precision in the counts, simplicity of operation, low power consumption and long-term dust tracking are the key aspects of the proposed system, that could replace the current monitoring strategies usually relying on manual inspection of witness samples (e.g. silicon wafers or adhesive tape-lift samples) placed in the vicinity of the spacecraft hardware.