QCM SENSORS FOR CONTAMINATION MONITORING IN SUPPORT TO NEXT CUBESATS AND SMALL SATELLITES MISSIONS

Quartz Crystal Microbalance (QCM) based sensors were applied in the past on-board small satellite missions, e.g. SMART-1, SDS-4 missions (Paita 2012, Nakamura 2013) to monitor the molecular contamination coming from outgassing sources of spacecraft materials that can degrade critical spacecraft surfaces, such as optical systems, solar panels, thermal radiators and thermal management systems (Benner 1998, Wood 1996).

Thus, QCM sensors are suitable instruments to monitor step by step these degradation processes which occur in space conditions and to characterize the deposited compounds by using the Thermogravimetric Analysis (Dirri 2016).

In the past years, an Italian Institutes Consortium developed CAM (Contamination Assessment Microbalance), for monitoring in-orbit contamination of sensitive surfaces and payloads on ESA`s future satellites, and recently developed CAM-LAB i.e., for ESA laboratory applications. These devices are low mass (100 grams for the sensor head), low volume (smaller than 5x5x5 cm3) and low power consumption (less than 1.5 W) sensors.

The device is composed by: 1) Sensor Head, containing a sensing crystal (which measures the deposited contaminant mass), a reference crystal (reference), their related Proximity Electronics (PE) and Temperature Control System (TCS); 2) Main Electronics Unit (MEU); 3) Harness; 4) User Interface (UI). The main innovations of CAM and CAMLAB are to measure directly the crystal temperature (better than 0.1°C), larger measurable mass range (up to 700 µg/cm2) and larger operative temperature range (from -80°C to 130°C) compared with previous QCM devices and the possibility to easily change the sensitive elements (i.e. crystals). The instruments concept and performance are presented.