Instrumenting an Earth Satellite
October 1958 Popular Electronics
October of 1958 when this article was written, a mere year had passed
since the successful launch of Sputnik and a few months later the
launch of Echo satellites - the first ever for Russia and the USA,
respectively. Prior to that time all satellites were conglomerations
of rock, metal, and/or gas. There were no manmade satellites except
for a couple remnants of test rockets that happened to reach orbital
heights. That Ronald Michael Benrey, a highschooler of the day,
would design and enter an "Earth Satellite" to demonstrate some
of the technology needed to an actual orbiting satellite was a phenom.
Most people hadn't even learned to spell "satellite" yet. His creation
took second place in the National Science Fair and first prize in
the USAF's Awards Program.
October 1958 Popular Electronics
Table of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
published October 1954 - April 1985. All copyrights are hereby acknowledged.
Instrumenting an Earth Satellite
By Mike Bienstock
(är'gus), n. | L., fr. Gr. Argos.
| 1. Gr. Myth. A hundred-eyed monster set to watch Io. 2. A watchful
Webster's definition of Argus is incomplete. In
Greek mythology, Argus has another connotation - it denotes the
starry heavens. In all respects, it is a fitting name for a model
satellite - "Argus I" - built by Ronald Michael Benrey and entered
in the National Science Fair.
The satellite took second prize
at the Fair and took first prize in the Air Force's Awards Program,
as well as receiving other citations. While it doesn't have the
100 eyes of the mythological Argus, it does have seven "eyes" -
sensors designed to "see" such things as temperature, ultraviolet
light, and micrometeorites-as well as two "voices" - transmitters
to relay the information to receivers.
Prize-winning Science Fair model reels off space secrets at the
push of a button
A view of the "works" in Argus I. Note that almost all components
are cased in plastic to allow full visibility - the metal box
at bottom houses the "Brain".
The designer of the satellite is shown at making an adjustment
in an equatorial thermistor sensor which registers skin temperature.
Diagram shows frequencies used by satellite.
Interior of satellite looks like this from the top. Equipment
is mounted on circular sheet of Plexiglas which rests against
The satellite shell is made of Plexiglas,
18" in diameter, in two hemispheres. Most of the components are
mounted in plastic boxes within, for visibility.
antennas in place, "Argus I" measures 54" in diameter and weighs
20 pounds. With batteries, it weighs 30 pounds. It is completely
transistorized, using 15 transistors in all. Total cost of the project
was about $200.
Ground Control. When
set up, the ground control equipment consists of a modified radio
control transmitter operating on 27.255 mc. and three receivers,
one tuned to the constant frequency of satellite transmitter Number
I (820 kc.,) and the other two to the frequencies of transmitter
Number II (1220 and 1300 kc.).
To conserve battery power,
one of the satellite's transmitters is silent until keyed by the
ground transmitter. The satellite carries a two-transistor receiver
to pick up the R/C ground interrogation signal, automatically keying
the "Brain" into its instrumentation cycle.
System. If "Argus I" were put into orbit, it would telemeter
the following information back to earth:
In addition, it shows the "solar aspect" (whether the sensor faces
or turns from the sun, indicating the satellite's attitude toward
- Skin temperature at two points (at the satellite's pole
- Internal temperature
- Number of strikes by micrometeorites at two points on satellite
pole and equator)
- Ultraviolet radiation
The basic circuit in the telemetering system is
shown in the schematic. The pulse rate of the unit (a metronome,
in effect) is varied by using a resistance changing sensor in place
of a variable resistor. Such sensors include a thermistor for temperature,
photocell for ultraviolet rays, and erosion gauge for micrometeorites.
The erosion gauge is a mirror with the paint backing carefully
removed with a cotton pad dipped in nail polish remover, or it can
be a photocell with an opaque coating. In the case of the former,
the "sandblasting effect" of micrometeorites erodes some of the
silver from the back of the mirror, changing the resistance; in
the case of the latter, the erosion allows more light to get through
to the cell. In this way the sensor-pulser unit's pulse rate is
a function of the phenomenon measured.
Cycle. The output of these units is amplified and each
pulse keys the transmitter via a keying relay. Each pulser is turned
on, hooked to the proper sensors and connected to the transmitter
by the "Brain." This consists of a "timed" 22-position five-deck
stepping relay which advances one position every five seconds, giving
"Argus I" a programmed instrumentation cycle. By "turning off" the
Brain timer by means of radio control, the cycle can be stopped
at any point for prolonged observation of one physical phenomenon.
You Can Record the Satellites
You can join in the greatest of all science experiments - the
scouting of space by the IGY satellites. A new Audio Devices booklet
describes how to use a modified FM broadcast receiver in conjunction
with a stable communications receiver to tune in the signals from
the satellites. With your tape recorder, you can record the latest
"news" from the heavens about meteors, ultraviolet radiation, and
other space phenomena.
This booklet not only tells you how
to make and interpret the satellite recordings but, most important,
it explains how you can determine if your recordings have value
to the official satellite project. For your copy of "You Can Record
the Satellites," see your audio dealer or send 10 cents to Audio
Devices, Dept. PE-10, 444 Madison Ave., New York 22, N. Y.
A second transmitter is included to allow the listener to know
when the instrumentation cycle is starting and when the Brain is
advancing. Both transmitters are one-transistor c.w. oscillators
with a power input of 15 mw., and are fed by a 15-volt hearing
separate ultraviolet photocell changes the capacitance of the tuned
circuit of transmitter Number II. As this sensor alternately faces
and turns from the sun, the frequency of the transmitter is changed,
switching from 1220 to 1300 kc. The frequency difference is relatively
large so that the natural Doppler shift doesn't affect the solar
aspect indication. Sensitivity is low, so starlight, moonlight or
earth glow doesn't affect the sensor.
The radio control
receiver in the satellite is tuned to a frequency of 27.255 mc.,
and is powered by two 1.5-volt penlight cells and a 22.5-volt battery.
The transmitter, a typical radio control unit, has a 3.2- watt input.
Pulses of the instrumentation cycle, varied by the sensors from
five beats to one-half beat per second, sound like short, staccato
"beeps" typical of the Sputniks.
Block diagram outlines functions of the model
The cycle is as follows: recognition signal 10 seconds; equator
mic. meteorite - 20 seconds; polar mic. meteorite-15 seconds; equator
temperature - 15 seconds; equator UV radiation - 35 seconds; polar
temperature-10 seconds; internal temperature - 5 seconds; and solar
aspect - 1/3 second every 5 seconds. Total - 1171/3 seconds. Duration
of the cycle is variable from about 40 seconds to about 235 seconds.
Exhibit of Argus I which netted Ronald second prize at the National
Science Fair. He is holding R/C transmitter used to query satellite.
Pulser circuit above feeds sensor information to transmitter,
where it is sent in its proper sequence at a signal from the
Decoding. Equipment needed to decode
the cycle includes three receivers, Doppler effect correction devices,
a graph-type recording counter with device for noting solar aspect,
and interferometer (if desired). The beep rate is counted by the
graph counter and notations are made by the operator regarding which
phenomenon is being recorded. The number of beeps per time unit
is then plotted against a prepared graph.
power supply consists of an NT6 (Willard) 6-volt storage cell for
the Brain, and eight 15-volt hearing aid batteries in addition to
the 22.5-volt battery and two 1.5-volt penlight cells.
is provision in the Brain for the use of cosmic ray detectors, and
the versatility of the satellite is further enhanced by universal
connections which allow change of instrumentation simply by Changing
If "Argus I" were to be set in orbit, a vertical
axis spin would be imparted by the last stage of the rocket. Chances
are it will never see the undiluted light of space. However, in
its earth trials, the satellite performs its mission perfectly.
Perhaps it will serve as a prototype of things to come.
The satellite's designer, lives in the Bronx, New York, and has
just entered Massachusetts Institute of Technology. Ronald plans
to major in physics and expects to go on and make his career in
the field of electronics.