A REAL TIME PARTICLE FALL-OUT MONITOR WITH HIGH MASS SENSITIVITY AND PARTICLE SIZE SEGREGATION

THE SEDIMENTATION OR FALLOUT OF AIRBORNE PARTICLES CAN SERIOUSLY DEGRADE THE PERFORMANCE OF CRITICAL SURFACES ON THE ORBITER AND SPACE-BOUND PAYLOADS. AT PRESENT, THE RECOMMENDED METHOD FOR MEASURING PARTICLE FALLOUT CONTAMINATION IS THE WITNESS PLATE WHICH INTEGRATES THE PARTICLE FALLOUT OVER SEVERAL DAYS. THE PARTICLES AND FIBERS COLLECTED ON THE FILTERS ARE SIZED AND MANUALLY COUNTED USING OPTICAL MICROSCOPY TO DETERMINE THE NUMBER OF PARTICLES-FIBERS PER SQUARE FOOT PER 24 HOURS. THIS METHOD IS TEDIOUS, TIME CONSUMING, AND PROVIDES ONLY INTEGRATED DISTRIBUTIONS WITHOUT THE FINE STRUCTURE OF INDIVIDUAL EVENTS. IT WOULD BE OF GREAT ADVANTAGE IF PARTICLE FALLOUT COULD BE MEASURED IN REAL TIME SO THAT SOURCES OF CONTAMINATION COULD BE IDENTIFIED AND REMOVED IN A TIMELY FASHION. IN THIS SOLICITATION WE PROPOSE AN ADVANCED AND INNOVATIVE APPROACH FOR THE MEASUREMENT OF PARTICLE FALLOUT CONTAMINATION IN REAL TIME, THE ELUTRIATOR QUARTZ CRYSTAL MICROBALANCE (EQCM). THIS INSTRUMENT WILL SEPARATE AIRBORNE PARTICLES ACCORDING TO SPECIFIC AND SELECTABLE CUT-OFF SIZES, COLLECT AND WEIGH THE PARTICLES IN REAL TIME ON A SENSITIVE MICROBALANCE, AND RETAINS THE COLLECTED PARTICLES FOR POST ANALYSIS BY OPTICAL OR ELECTRONMICROSCOPY. THE HIGH MASS SENSITIVITY OF THE EQCM COULD DETECT A SINGLE 25 MU M PARTICLE OF MASS DENSITY 2 G/CM(3).