Abstract View
Condensation Particle Counting in Micro-gravity: Measurements Aboard the International Space Station
Gregory Lewis, Nathan Kreisberg, Steven Spielman, SUSANNE HERING, Marit Meyer, Aerosol Dynamics Inc.
Abstract Number: 543
Working Group: Instrumentation and Methods
Abstract
Long-term monitoring of ultrafine particle concentrations aboard spacecraft is a challenge. The instrument must be capable of measuring low concentrations of the order of 1 - 10 particles per cubic centimeter that characterize background levels in the filtered cabin air, as well as concentrations approaching 100,000 arising from sources. This concentration range is most easily spanned through condensation particle counters (CPCs). However, the liquid reservoirs required for long-term CPC operation are incompatible with the micro-gravity environment of space craft. Nor are the organic vapor emissions from alcohol-based CPCs allowed.
Presented here is a new, wick-sensor equipped, water-based condensation particle counter specifically designed for long-term use aboard the International Space Station. This NASA-MAGIC CPC uses the three-stage, “cold-warm-cold” architecture of the MAGIC® CPC wherein the walls are lined with a single wick. This wick serves as the water reservoir. Within the cold stages the wick captures water from the flow, and within the warm stage water evaporates from the wick to create the supersaturation needed for particle activation and growth. The wick transports water among these stages via capillary action. With correctly controlled operating temperatures, and with sufficient humidity in the sampled air stream, the net water consumption is zero. The NASA-MAGIC CPC incorporates a sensor to detect the wick moisture level, and this signal is used to regulate the operating temperatures to maintain a fully moistened wick while avoiding excess condensation. The instrument also has a priming mode that enables an initially dry wick to moisten itself from the humidity within a sampled air flow, a feature that allows the system to be launched with a dry wick.
NASA-MAGIC was launched in October 2020, and was deployed aboard the International Space Station in late November. Since that date, a period of 5 months at the time of this writing, NASA-MAGIC has returned a continuous stream of 1-s particle number concentration data.