Liquid water fade margin requirements for infrared and millimeter wave runway imaging sensors in fog |
| |
Authors: | Robert E Marshall David A de Wolf and Christos Kontogeorgakis |
| |
Institution: | (1) Research Triangle Institute, One Enterprise Parkway, Suite 310, 23666 Hampton, Virginia;(2) Bradley Department of Electrical Engineering, Virginia Polytechnic Institute and State University, Austria |
| |
Abstract: | Liquid water content and particle size distribution at each ten meters in the vertical for a deep advection fog and a shallow
radiation fog are analyzed to determine the liquid water loss at millimeter and infrared wavelengths. The liquid water fade
margin is calculated along a three degree glideslope in each fog from the current height above the runway to the touchdown
point. Millimeter wave fade margin requirements are calculated from the vertical distribution of bulk liquid water content
and infrared fade margin requirements are predicted from the vertical distribution of dropsize. Fog dropsize distributions
for both fog layers are well fitted to a gamma distribution with a median drop diameter of approximately 9 microns. Millimeter
wave imaging sensors operating in a shallow radiation fog are shown to require less than 1 dB of one-way liquid water fade
margin. In the deep advection fog, one-way liquid water fade margin requirements at 8.6 mm, 6.8 mm, and 3.2 mm are predicted
to be 1, 2, and 6.7 dB respectively. In comparison, the one-way liquid water fade margin requirements at near, middle, and
far infrared wavelengths are two orders of magnitude greater than at millimeter wavelengths and indicate the fog layers are
opaque to infrared imaging sensors even near the touchdown point. The specific attenuations predicted in the two fogs are
consistent with previously reported values. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|