Morphology of ionosphere using radio signals from earth satellite

Swenson, G. W.

Yeh, K. C.

English

NASA Technical Reports Server

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ICATEGORYI 
Progress Report No. 9 
A Theoretical and Experimental Study of the Ionosphere 11 
Using Radio Signals from Earth Satellites" 
Grant Number NsG 24-59 
from 
The National Aeronautics and Space Administration 
G. W. Swenson, Jr., Principal Investigator 
K. C. Yeh, Co-Investigator 
Period Covered: January 1, 1964 to June 30, 1964 
July 16, 1964 
The E lec tr ical Engineering Research Labor at ory 
University of Illinois 
with the cooperation of the 
University of Illinois Observatory 
Urbana, Illinois 
https://ntrs.nasa.gov/search.jsp?R=19650020052 2020-03-17T01:59:06+00:00Z
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I n t r oduc t ion 
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This report describes the continuation of research on the morphology 
of the ionosphere, using as the general method the observation of perturba- 
tions induced by the ionosphere on radio signals from earth satellites. 
The program has been underway since the early part of 1958, having been 
instituted with the launching of the first artificial satellite, Sputnik I. 
The principal subjects for this research are the investigation of small 
scale ionospheric irregularities by means of scintillation of radio signals 
from satellites and the investigation of the total electron content of 
the ionosphere by observation of the Faraday rotation of the planes of 
polarization of radio signals from satellites. In addition theoretical 
studies have been undertaken concerning the phenomena under experimental 
investigation. 
Field Operations 
The previously established satellite-monitoring stations at Urbana, 
Illinois; Houghton, Michigan; and Baker Lake, Northwest Territories, 
Canada were continued in operation to record the signals of satellite 
1961 Omicron, Transit 4A. The station at Adak, Alaska has been continued 
on a standby basis. As the attempted launching of the S-66 Ionosphere 
Beacon Satellite on March 19, 1964 was unsuccessful, the mission of the 
field stations remained unchanged from that of the previous reporting period. 
No major changes in instrumentation have been made at any of the field 
stations. A new receiver power supply and a pair of Model B receivers have 
been sent to Adak. An all-transistor, six-channel, high-frequency, time- 
signal receiver has been designed and the prototype installed at Houghton. 
2 
Data Analysis 
Mr. Kranz has been supervising the analysis of scintillation data from 
satellites 1959 Iota, 1960 Eta and 1961 Omicron. To date the scintillation 
indices for all records between August 1960 and August 1962 have been tabu- 
lated, thereby filling in a gap which previously existed. Thus, a continuous 
record of the scintillation index as seen from the Urbana station is available 
during the descending phase of the previous sunspot cycle,, In order to 
fill in the gap from 1960 to 1962, it was necessary to compute ephemerides 
for all three satellites mentioned above. As the orbital elements were 
available in diverse form for the various satellites, this part of the 
project involved a considerable amount of computer programming. 
Dr. J. P. McClure completed his Ph.D. thesis involving a study of the 
heights of scintillation-producing irregularities, A Isrge hi,imber of 
observations were used, extending over a period of four years, to study 
the diurnal, seasonal, and latitude variations of the heights. The 
abstract of Dr. McClureqs thesis is quoted below: 
Scintillation of radio signals from artificial earth satel- 
lites has been studied with a network of spaced receivers. The 
height of the irregularities responsible for scintillation was 
measured by the cross-correlation method for 130 satellite passages. 
Theoretical calculations show that the cross-correlation method 
used gives the average irregularity height when irregularities are 
uniformly distributed over a finite height range. The irregularity 
height measurements were made continuously for all scintillation 
observed sufficiently close to the receiver network. The irregu- 
larity height in the F-region was found to be fairly constant for 
about 2/3 of the passages examined, and to be more or less variable 
about 1/3 of the time. The average height gradient for individual 
cases where the irregularity height is not constant was near zero. 
Increases in irregularity height to the north and to the south 
occurred with approximately equal probability. Height gradients 
were seldom uniform for more than 50-100 km. The average height 
of all F-region irregularities increased to the north. This was 
not due to uniform layers of irregularities gently sloping upward 
. * '  
3 
to the north, but to irregularity patches, large and small, being 
higher, on the average, in the north. The heights of the irregu- 
larities in the E-region below 130 km were constant, and had no 
gradients, unlike the irregularities in the F-region. 
Sufficient data were obtained to determine the diurnal varia- 
tion of the irregularity height distribution. The data show 
conclusively that most daytime scintillation originates in the 
E-region near 110 km height, and that most nighttime scintillation 
originates in the F-region at heights between 300 and 400 km. 
When E or F-region irregularities were observed near an ionosonde, 
they were nearly always accompanied by sporadic-E or spread-F 
echoes on the ionogram. The F-region irregularity height distri- 
bution was considerably broader after midnight than before midnight. 
There were not enough data to tell whether or not there was any 
seasonal variation of the irregularity height distribution. 
Theoretical calculations resulted in a cross-correlation 
function describing the changes in the signal strength pattern 
on the ground which are observed in spaced receiver experiments. 
A concise expression was obtained for the cross-correlation as 
a function of the thickness and average height of a uniform slab 
of irregularities, the size of the irregularities, and the re- 
ceiver spacing. After the cross-correlation has fallen to 0.5, 
it is approximately an inverse function of distance. These cal- 
culations are based on work in scattering theory by Yeh. A 
formula deriver! f r c m  the diffraction theory by James can be 
obtained as a special case of the cross-correlation function 
developed here. The cross-correlation function is applied to 
experimental data and the thickness of the layer of irregularities 
is found. For F-region scintillation the thickness varied from 
50 km to over 300 km, with an average of approximately 120 km, 
Under the direction of Dr. K. C. Yeh, electron content curves derived 
by Faraday-rotation analysis for the period February 1962 to December 1963 
have been plotted, for both north-bound and south-bound passages of Transit 
4A. These curves, when compared with similar curves obtained in the period 
September 1958 to December 1959 and published in J. G, R, 66, p. 1061, -
clearly demonstrate the sunspot dependence. At present the Faraday analysis 
has been carried to May 1964. It is hoped to have the data taken during 
the period December 1959 to February 1962 analyzed in the next six months. 
In connection with the Faraday-rotation work, it is necessary to 
know the geomagnetic field at various points above the earth's surface. 
4 
Earlier work of this project resulted in the "&Chart method" and in a 
magnetic-field subroutine for the old Illiac I computer, both of which 
were widely used by researchers at other institutions. With the retire- 
ment of the Illiac I, it became necessary to reprogram the magnetic field 
problem for the IBM 7094 computer. This has been done by Mr. R, H. Eckhouse, 
using Fortran, The new magnetic field program is also used as a subroutine 
in a program for determining total electron content from Faraday-effect 
null-positions on the satellite records. 
A set of magnetic field data was computed for Dr. Somayajulu of the 
National Physical Laboratory, New Delhi. 
Facilities and EauiDment 
No major additions to the facilities were made during the report period, 
with the exception of the phase-locked Doppler receiving system for the 
EGO beacon. This equipment was received from Smyth Research Associates 
and is being maintained on a standby basis while awaiting the launching 
of the Eccentric Orbiting Geophysical Observatory. 
Theoretical Studies 
Jointly with the eclipse project sponsored by NSF GP-411 a study of 
Fa-region aeronomy has been initiated. As a by-product, it is discovered 
that the diurnal and the irregular thermal expansion of the neutral atmos- 
phere may have a very important effect on the formation of the ionosphere-- 
it tends to lift up the ionosphere. Its whole effect is equivalent to 
replacing the Earth's gravity by some effective value which may even be- 
come negative at some heights. This work is being done by Dr. KO C. Yeh, 
Dr. J. F. Phelan, and Mro T. R, Pound. 
5 
Pub1 icat i ons 
The following publications appeared during the report period: 
J. P. McClure, "Polarization Measurements during Scintillation of 
Radio Signals from Satellites," Journal of Geophysical Research, 
69, No, 7,  April 1, 1964. -
J. P. McClure, ''The Height of Scintillation-Producing Ionospheric 
Irregularities in Temperate Latitudes," Journal of Geophysical 
Research, 69, July 1, 1964. 
K. C. Yeh and G o  W. Swenson, JrOp "F-Region Irregularities Studied 
by Scintillation of Signals f r o m  Satellites," Accepted by NBS 
Journal of Research, Section D, Radio Science, August 1964. 
N. C. Mathur and KO C. Yeh, "Multiple Scattering of Electromagnetic 
Waves by Random Scatterers of Finite Size," Accepted by Journal 
of Mathematical Physics,, 1964. 
91 Richard H. Eckhouse, Jr., Fortran Computer Program for Determining 
the Earth Magnetic Field," Electrical Engineering Research Labora- 
tory, University of Illinois, February 1, 1964. 
J. P. McCliire ax! G .  8 ,  Sweiisuii, 5roj "Beacon Satellite Studies of 
Small Scale Ionospheric Inhomogeneities," Electrical Engineering 
Research Laboratory, University of Illinois, May 1964, 
Per sonne 1 
The following persons were involved in project activities during the 
report period: 
Dr, G o  W. Swenson, Jr. 
Dr. K. C. Yeh 
Dr, John Po McClure 
Dr. James F, Phelan 
Bernard Flaherty 
Anthony Szelpal 
Carl Stubenrauch 
Paul R. Kranz 
Richard H ,  Eckhouse, Jr 
Principal Investigator 
Co- Investigator 
Research Assistant 
Research Associate 
Electronic Engineer 
Electronic Technician 
Research Assistant 
Research Assistant 
Research Ass is t ant 
Note: Several hourly student assistants are also employed. 
* . r  
Paid from project funds during summer only, 
* 
1/2 time 
1/2 time 
1/2 time 
1/2 time 
1/3 time 
Full time 
1/2 time 
1/2 time 
1/2 time (resigned 
June, 1964) 


A theoretical and experimental study of the ionosphere using radio signals from earth satellites progress report no. 9, 1 jan. - 30 jun. 1964

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