Time Delay of Terrestial Light Pulses Propagating through Clouds to Satellite Systems
Abstract
A method is described and applied for interpreting optically filtered all sky photographs so as to generate curves of the time dependent probability that a photon emitted by an isotropic source near the earth's surface will reach a satellite at any elevation and azimuth in the sky. Two basic concepts are involved: first, that the probability at lambda = 0.76 micron for absorption of light by atmospheric oxygen is proportional to the square root of the dwell time of the light in the atmosphere and second, that a time dependent reciprocity theorem exists allowing observations of the skylight incident on a ground based detector to be interpreted in terms of the probability that a photon starting at the detector can reach a satellite in the direction of the sun. Detailed theory and operating equations were developed and appropriate equipment was built and operated. Computerized reduction of microdensitometer scans of the all sky photographs led to values of mean time delay and transmission for 125000 equal elements of solid angle in the sky. These were summed to generate the time dependent probability. Photographs made at Kennedy Space Center were used to generate delay curves for seven satellite directions on nine separate occasions.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 07, 1980
- Accession Number
- ADA087242
Entities
People
- H. S. Stewart
- L. B. Woolaver