REAL-TIME DETECTION OF PERFORMANCE DEGRADATION OF THE FORWARD-SCATTERING SPECTROMETER PROBE

A method for detecting malfunctions during collection of data with the forward-scattering spectrometer probe (FSSP) is discussed. Droplet spectra measured with the probe are not sufficient to alert operators of probe failures, such as those caused by fogging or icing of the optics. Exact solutions of the coincidence process and application of these formulas, using additional parameters provided by the FSSP, yield estimates of the transit time of the droplets through the laser beam. Comparison of these estimates with expected values derived from aircraft speed can be used to detect a variety of FSSP malfunctions. An example of such an analysis using data from a flight through supercooled cloud is presented.