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<br />4.7 Forward-Scattering Spectrometer Probe <br /> <br />A Particle Measuring Systems (PMS) Model FSSP-lOO, designed for in-situ particle size <br />measurements, was installed outboard and below the left wing of the research aircraft. A laser beam <br />is focused to illuminate a sample area in a transverse air flow from one side while collecting optics <br />view the area from the side opposite the flow. Particles passing through the sample area scatter <br />energy in proportion to their size to two solid-state photo-detectors via a beam splitter for <br />measurement. The probe has four overlapping size ranges with each range divided into 15 linear size <br />intervals, providing 60 channels in a 0.5-47 J-lm range. For this application the instrument was <br />operated on range 0, which spans 3-47 J-lffi, or range 1, for 2-32 tim. <br /> <br />Specifications <br />Range: 3 to 47 or 2 to 32 J-lm (15 bins) <br />Resolution: 0.5 J-lm <br /> <br />Calibration <br />Manufacturer: Performed 2 May 1988. <br />Droplet Measurements Technology (DMT): Performed May 1992. <br />Laboratory: Prior to the field experiment, the calibration of the probe was verified by passing <br />monodisperse latex or glass particles through the sample area. Also, a spinning slit <br />designed by DMT was used to check calibration. <br />Onsite: Simple calibration checks were accomplished using the spinning slit and calibrated <br />latex or glass particles. <br /> <br />4.8 Long Range Navigation (Loran) System <br /> <br />The Advanced Navigation Inc. (ANI) Model 7000 Loran-C was installed (early 1985) as a <br />permanent navigational aid for position data on the research aircraft. Loran-C is a third generation, <br />stable, low frequency radio navigation system which broadcasts from a chain of three to five land- <br />based transmitting stations separated by several hundred miles. Within the chain, one station is <br />designated the master station, and the other stations are secondary stations. Signals transmitted from <br />the secondaries are synchronized with the master signal. The on-board Loran-C receiver measures <br />the slight difference iil time that it takes for these pulsed signals to reach the aircraft from various <br />pairs of stations and from different chains. That constant time difference between corresponding <br />secondaries and masters establishes a line-of-position that is used for navigation. Position as a <br />function of latitude and longitude is the processed output. Wind direction and wind speed are <br />computed in real time using the Loran-C output, calculated true airspeed, and aircraft heading <br />information from other onboard navigation instruments. Latitude and longitude are converted to <br />decimal degrees. <br /> <br />13 <br />