TECHNICAL DISCUSSION ATTACHMENT IV ELFIN FIELD TEST PROGRAM

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78-05288A000100020003-7
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 6
• Document Creation Date: December 23, 2016
• Document Release Date: August 14, 2013
• Sequence Number: 3
• Publication Date: July 1, 1962
• Content Type: REPORT

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TECHNICAL, DISCUSSION
ATTACHMENT IV
ELFIN FIELD TEST PROGRAM
DOCUIvIEI
NO C.IHANO17.: IN OV.S3.
-GLASS. Ci-li.NGED TO: TO nc4
NExT REVIEW DATE:
AUTH: HR 79;2
DATE: _9,07.; Mei- REVIEWER: __213_
This Document contains information affecting the
National Defense of the United States, within the
meaning of the EspionaTe Laws. Title 18, U.S.C.,
Sections 793 and 794, the transmission or revela-
lion of which in any manner to an unauthorized
person is prohibited by law.
rannwarriai (;)`/
Declassified in Part - Sanitized Copy Approved for Release 2013/08/14: CIA-RDP78-05288A000100020003-7
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1. INTRODUCTION
This proposal is for a program which is a logical continuation of
the present Elfin program. The present program is for the development
of electrolytic techniques for measuring low energy microwave fields by
the use of an antenna and diode to provide a current to be integrated by
an electrolytic cell. The proposed program is for field and laboratory
testing of these devices to demonstrate their sensitivity, dynamic range,
and frequency discrimination ability.
The present research and development program has attained signifi-
cant success insofar as it has produced electrolytic cells of sensitivity
beyond that which was initially proposed. The present electrolytic cells
are capable of integrating quantities of charge as small as 10 millimicro-
coulombs and allowing readout of this quantity of charge in a time interval
of 10 seconds with an accuracy of a few percent. The proposed continuation
of this program will result in the taking of the Elfin devices composed of
the electrolytic cell, diode, and antenna to the vicinity of various radars,
exposing the antennas to the radars for fixed intervals of time, analyzing
the results and comparing with predicted results. Additional work will be
continued in the laboratory to improve the devices on the basis of the field
tests and to devise new devices capitalizing on the sensitivity of the
electrolytic cells which have been developed.
2. STATUS REPORT ON PRESENT STUDY
The review of the progress reports on the present study will indicate
that considerable progress has been made since the initiation of this study
in the integration of very small currents. It was found, as anticipated,
that considerable care is necessary in the preparation of the cells to insure
maximum cleanliness. Indeed, numerous rinsings with distilled water are
necessary after the cells have been cleaned with various acids to remove
traces of the acids from the cells. Of particular importance in the develop-
ment of high sensitivity cells is the manner in which electrodes are made
and assembled in the cells. This one area has, perhaps, caused more
difficulties than any other and the resolution of these difficulties has led
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to greater improvements in sensitivity than the development of any other
area. It has been found important to keep the electrode area rather small
for various reasons, thus 3 mil platinum wire is used in the assembly of
the electrodes. Likewise, it was found that a very good match between
the thermal coefficient of the wire and that of the glass is important to
insure that the glass is sealed well to the wire to avoid crevices which
can capture the electrolyte solution. The result is that cells are presently
made out of soft glass which operate at readout currents as small as a
millimicro ampere. In order to keep the impedance of the cell very low,
it is necessary to assemble the electrodes in such a manner that they are
only a few thousandths of an inch apart. The resulting cells are T-shaped
and, being made of soft glass, have a certain degree of fragility. It is
anticipated that in the field test program these cells can be properly imbedded
in a plastic resin along with the antenna and diode in such a manner as to
provide a fairly rugged unit.
3. FIELD TEST PROGRAM
The purpose of the field test program will be to demonstrate the
sensitivity and dynamic range of the Elfin devices under carefully con-
trolled field test conditions. A second goal of the program will be to
simulate accurately operational use of the devices and to determine and
provide solutions for various operational problems that may arise. The
overall objective of the program will be to provide Elfin devices and
operational procedures which can be put into practice without further
development or testing.
In order to present a fair sample of data, simulating operational
conditions, it will be necessary to perform measurements in the vicinity
of several radars with several different terrain conditions. It is anticipated
that the radars used will be L- and S-band air defense acquisition radars.
However, traffic control radars at airports may also be used. Many
problems have been noted which will contribute to errors in determining
the radar power by the Elfin field measurements. In particular, the
antenna pattern and its gainJn the vertical direction mak
integration
integration of the energy at surface level will not lead to an accurate
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Declassified in Part - Sanitized Copy Approved for Release 2013/08/14: CIA-RDP78-05288A000100020003-7
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estimate of the integrated energy throughout the hemisphere. An additional
problem might be the use of the Elfin device too close to the radar antenna
yielding pulses of height sufficient to drive the diode into the linear region
and out of the square-law region so that the relationship between incident
radar energy and current through the electrolytic cell is not predictable.
It will also be important to know whether or not the radar is actually
radiating during the test conditions since radars are frequently shut down
for repair or testing even through the antennas may appear to be operating.
Because of these problems and others, it will be necessary to assemble
a fair assortment of equipment to accompany the engineers and the Elfin
devices on the field test programs. It will also be more efficient to do the
readout of the cells at the field test location in order that time is not lost
in transportation from the site to the laboratory and back. This will allow
several measurements to be made with a single cell comparing its repro-
ducibility at given site locations from one series of measurements to the
next. It is planned, therefore, to assemble equipments such as a radar
receiver, cathode ray oscilloscope, microvolt ammeter, chart recorder,
and others and mount these equipments in a small trailer which can be
taken to the measurement site. It will be necessary, of course, to have
the cooperation of the officers in charge of the site so that the collection
of data will not result in any security difficulties.
Additional goals of the field test program will be to provide operational
testing of more elaborate devices than the simple Elfin device which has
been developed. In particular, it is intended to measure the frequency
discrimination capability of a series of Elfin devices with different antennas
or resonant circuits. Other devices using the basic Elfin principle under
consideration are circuits for determining pulse width, PRF, and other
characteristics of the radar signal. Of particular importance will be
the development of techniques to measure antenna beamwidth and gain for
rotating antennas.
A final phase of the field test program will include simulation of
near operational conditions where one or two Elfin devices will be carried
in the clothing of an engineer or technician and operated in the region of
a particular radar. The actual experiment will be done by an individual
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not familiar in detail with the program but having received only simple
instructions as to how to operate the equipment. On returning to the
laboratory, the device will have the charge accumulated determined,
and from this an estimate of the radar power will be made and compared
to previous field measurements and knowledge of the radar system itself.
? 4. LABORATORY PROGRAM.
In order to support the field test program, a certain amount of
backup work in the laboratory will be necessary. It will be necessary
to prepare the devices, check them out in the laboratory, and check
them out upon return from the field test experiments.
Additional laboratory work will be done to continue the improvement
of the electrolytic cell sensitivity since the limit of its capability has not
'yet been reached. Additional application of the cells and their enhanced
sensitivity will be investigated along the lines of the application originally
intended. To this end, one can almost specify an ideal Elint system for
this kind of a device which will determine a number of radar parameters
such as power, frequency, PRF, pulse width, polarization, antenna beam
width and gain, the presence of simultaneous multiple frequency emissions,
frequency jumping, variation in PRF, pulse compression, and scan period.
If all, or a large number of these parameters could be determined in a
device which required little or no power of its own, and could be packaged
in very convenient form, a considerable advancement in electronic intelligence
will have been made. Preliminary analysis indicates that such a goal is not
beyond the realm of possibility.
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Declassified in Part - Sanitized Copy Approved for Release 2013/08/14: CIA-RDP78-05288A000100020003-7