Dust Accumulation Sensor Provides In Situ Monitoring
Sensors
Dust Accumulation Sensor Provides In Situ Monitoring (MSC-TOPS-143)
Features optical coating technology calibrated to quantify dust
Overview
Innovators working at NASA Johnson Space Center have developed a dust sensor for use in space environments that measures surface dust accumulation more effectively and accurately than solar cell-based methods. The Planetary Accumulation of Dust Sensor, or “PADS” for short, comprises a compact, puck-shaped form factor whose key component, a sensor disc, has a tunable optical coating from which dust accumulation is derived through measured changes in coating properties when heat is applied.
For planned Moon and other planetary-body missions (Mars, asteroids), there are significant needs to understand the impacts of the dust environ-ment to support design, operations, performance impacts, etc., for scientific and overall mission objectives. NASA believes the PADS device will be useful for ensuring remote equipment operators and astronauts are aware of dust accumulation on mission critical components (e.g., radiators, solar arrays) that could lead to mission complications.
The PADS device provides a solution to these needs in a simple, light-weight, low power device for measurement of dust accumulation in a space-based environment having undergone ground calibration and optimization of its key design features for the environment of interest. The Planetary Accumulation of Dust Sensor is at a technology readiness level (TRL) 6 (System/sub-system model or prototype demonstration in an operational environment), and is now available for patent licensing.
The Technology
Previous techniques for measuring dust accumulation, mostly de-pendent on solar cell output, were limited by their inability to distin-guish dust effects from other factors like incident radiation and radiation damage. These techniques were less effective in environ-ments with inconsistent solar flux and future missions, such as the Lunar South Pole, and lacked versatility in adapting to diverse envi-ronmental conditions. The PADS device embraces success over these challenges, and reflects enhanced features over prior iterations to also allow for space environments.
Key design features begin with the customizable mechanical design of the PADS device for use in space environments, heaters with imbedded precision temperature sensors, a selected optical coating for the device coupons that are calibrated on high-fidelity thermal modeling and validated with ground-based testing to simulate the space environment of interest (including dusting with simulants representative of the planetary-body soil/regolith), and a control circuit for precision control/matching of the thermal inputs to the sensor via the heaters. Retainers with mount isolators are implemented to ensure the stacked layers within the device do not dislodge during high vibration or gravitational loads during launch.
For operation, the PADS device is installed at the point of interest (e.g., space vehicle surface, extraterrestrial equipment) to quantify dust accumulation. Power and data transfer are done through cabling to the space vehicle system or can be provided standalone. A control circuit/algorithm adjusts the power to the heaters to precisely match the temperature setpoints. Ground testing in the simulated space environment conditions of interest creates a calibration plot of effec-tive emittance versus dust density, and allows determination of the degradation in emittance as the dust increases on the surface.
Testing on the PADS device has been completed in a simulated lunar environment and data has been collected to enable sensor calibration for its use on the Moon. It is currently poised for integration into a lander for flight testing.
Although the PADS device is intended for use in a burgeoning space industry and requisite environments – but given that the PADS device is partially comprised of programmable sensors in conjunction with optically coated coupons that can be tailored for custom use - it or its constituent components could be modified for terrestrial applications such as surface dust monitoring on photovoltaic panels or potentially combustible dust on various industrial surfaces.
Benefits
- Provides localized measurements of dust/regolith accumulation for space missions
- Compact size and minimal mass supports ease of integration and facilitates measurement proximate to point of interest
- Easily optimized for environment of interest through novel tuning
- Device is passive with no moving parts
- Minimal power draw; will support continuous or intermittent operations for extended durations
- Can operate remotely
- Device can be calibrated on the ground in simulated planetary conditions (e.g., vacuum environment with simulated dust/regolith)
- Inexpensive to fabricate and implement
Applications
- Space environment mission critical component dust accumulation monitoring
- Terrestrial photovoltaic panel dust accumulation monitoring
- Industrial surface combustible dust monitoring
Technology Details
Sensors
MSC-TOPS-143
MSC-27660-1
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