Based on variances of log-amplitude and phase fluctuations of radio occultation data received from orbital and fly-by missions, structure constant for Venusian planetary atmosphere has been estimated with high-confidence factor. Analysis indicates that effects of inhomogeneity, finite size, and superrefractivity of atmospheric turbulence cannot be ignored

Ishimaru, A.

Woo, R. T.

English

NASA Technical Reports Server

September 1974	 B74-10168 
NASA TECH BRIEF 17 ASA NASA Pasadena Office 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Method for Remotely Sensing Turbulence of Planetary Atmospheres 
. 
S
It is well known that turbulence in Earth's atmos-
phere affects radio communications. Practically everyone 
listening to a radio has sensed this phenomenon in the 
form of interrupted or noisy reception due to different 
weather disturbances and events in the upper atmos-
phere. Although uQcontrollable, turbulence is a major 
indicator of atmospheric properties. It can be studied 
through its effects on radio communication, which yet 
has much information to reveal on Earth's atmosphere 
as well as the atmospheres of other planets. Past 
interplanetary missions and experiments here on Earth 
have already made significant contributions to this 
study. 
Future interplanetary missions will involve atmos-
pheric entry probes to Venus and Jupiter, whose 
atmospheres are dense and are believed to be turbulent. 
For these missions, a phase-coherent communication 
system may be inadequate because of its inability to 
track the turbulence-induced fluctuations in the radio 
signals. Atmospheric turbulence and its effect on radio 
propagation, therefore, play a key role in the design of 
a successful iadio link with entry probes to Venus and 
Jupitci. 
It is clear that our knowledge of the turbulence 
ehaiacteristies of the atmospheres of Venus and Jupiter 
is vet  limited. Asa consequence, meaningful prediction 
ot the effects of this turbulence on communications is 
practically impossible. Useful information on the tur-
bulence characteristics, however, can be inferred from 
the radio occultation data received from the Mariner 5 
mission to Venus and the Pioneer 10 mission to Jupiter. 
The analysis of these data provides a technique for 
inferring the turbulence characteristics of a planetary 
atmosphere from the received radio signals. Since these 
data mequire no additional spacecraft equipment, they 
are essentially free and provide valuable information 
that otherwise would not be available.
Planetary turbulence is assumed to be localized and 
smoothly varying, with the structure constant varying 
exponentially with altitude. Rytov's method is used to 
derive the variance of the log-amplitude and phase 
fluctuations of a wave propagating through the atmos-
phere. It is shown that when the distance between the 
spacecraft and the planetary atmosphere exceeds L,/X, 
where L0 is the outer scale of turbulence (turbulence 
diameter), X being the wavelength of the propagating 
wave, the effects of inhomogeneity and the finite size 
of the turbulent medium become important. 
Based on the variances of the log-amplitude and 
phase fluctuations of the radio occultation data received 
from orbital and fly-by missions, the structure constant 
for the Venusian planetary atmosphere has been esti-
mated with a high-confidence factor. The analysis 
indicates that the effects of inhomogeneity, finite size, 
and superrefractivity of atmospheric turbulence cannot 
be ignored. 
Notes: 
1. This method may be of interest to communications 
engineers, meteorologists, and astrophysicists. 
2. Requests for further information may be directed to: 
Technology Utilization Officer 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: TSP74-10168 
Patent status: 
NASA has decided not to apply for a patent. 
Source: Richard T. Woo and

Akira Ishimaru of

Caltech/JPL
under contract to

NASA Pasadena Office 
(4PO-13154) 
Category 03,02 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United Stales 	 information contained in this document, or warrants that such use 
Coernmenl not any person acting on behalf of the United States 	 will be free from privately owned rights,
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Method for remotely sensing turbulence of planetary atmospheres

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