Spectrometers
MASPR
The Multiple-Angle Aerosol Spectrometer Probe (MASP) determines the size and concentration of particles from about 0.2 to 20 microns in diameter and the index of refraction for selected sizes. Size is determined by measuring the light intensity scattered by individual particles as they transit a laser beam. Light scattered from particles into a cone from nominally 30 to 50 degrees forward and 130 to 150 degrees backwards is reflected by a mangin mirror through a condensing lens to the detectors. A comparison of the signals from the open aperture detector and the masked aperture detector is used to accept only those particles passing through the center of the laser beam. The index of refraction of individual particles can be estimated from the ratio of the forward to back scatter signals. A calibration diode laser is pulsed periodically during flight to ensure proper operation of the electronics. The shrouded inlet minimizes angle of attack effects and maintains isokinetic flow through the sensing volume so that volatilization of particles is eliminated. Additional information available at http://code916.gsfc.nasa.gov/Public/Analysis/aircraft/tote/ baumgardner.html [Summary provided by NASA]