July 1957 Radio & TV News
[Table
of Contents]
Wax nostalgic about and learn from the history of early
electronics. See articles from
Radio & Television News, published 1919-1959. All copyrights hereby
acknowledged.
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Here is a great look inside the planning and operation of the "Minitrack"
systems used for
Project Vanguard to track the Sputnik, Echo, Explorer, and other
early Earth artificial satellites during the
International
Geophysical Year (IGY) activities. "Essentially, the [IBM 704's]
storage function works by means of doughnut-shaped cores, about
the size of pinheads, which are strung on a complex of wires in
such a way that several wires pass through each core. Combinations
of electrical impulses on these wires alter the magnetic states
of the cores. A line of cores, some magnetized and some neutral,
represents a number or other collection of symbols in much the same
way as a combination of dots and dashes stands for a word in Morse
code. Up to 32,768 of these 'words' can be stored in the 704's high-speed
magnetic core memory. Additional "words" can be held in auxiliary
storage by attaching magnetic drum units."
Tracking the Man-Made Satellite
By Max Gunther
A complex and elaborate "recording" system" will be used to keep
track of the tiny sphere after it is launched in space.
Some
time during the International Geophysical Year that begins July
1, 1957, there will culminate one of the most ambitious experiments
- and certainly the best-publicized - in all scientific history.
From the Patrick Air Force Missile Test Center on Cape Canaveral,
Florida, a tiny, man-made moon will be launched. It will be carried
by rocket to a height of 200 to 300 miles, then pushed horizontally
to a speed of 17,000 to 18,000 miles an hour. If all goes well,
it will then settle itself in an elliptical orbit around the earth,
there to stay for several weeks, or perhaps a year, or perhaps even
longer. Science will have taken its first major step into outer
space.
Nobody has ever tried anything like this before; hundreds of
uncontrollable variables make the outcome of the experiment impossible
to predict. One of the largest imponderables is the path that the
satellite will take. At this stage of the moon-making art, it is
impossible to control or foretell the exact speed of the satellite,
its height above the earth's surface, the inclination of its orbit
to the equator, or the orbit's shape. Thus, the tiny globe, measuring
less than two feet in diameter, could easily become lost to view
in the sky like a toy boat misplaced in the Atlantic Ocean.
To forestall any such comi-tragic ending to the experiment, scientists
plan to make wide use of electronic tracking and computing equipment.
At the heart of all satellite-watching operations will be the fastest
large-scale digital computer manufactured by International Business
Machines Corporation - the "704" Electronic Data Processing Machine.

Over-all view of the IBM 704 Electronic Data Processing
Machine which will calculate and predict the course of the
earth satellite at tremendous speeds. This installation
has been made at the "Project Vanguard" Computing Center
in Washington. D. C. Radio signals emitted by the satellite
will be relayed to this Center, where machine will process
the information and compute sphere's orbit. |
The 704 computer installation will be housed in Washington, D. C.,
in a large building already beginning to fill up with equipment.
This equipment will include not only a central data-processing or
calculation unit, but also a platoon of subsidiary units to handle
such functions as printing, reading, recording, and conversion from
one form of data-input (such as punch cards) to another (for example,
magnetic tape). This high-powered installation will be served by
its own power supply. It will also have its own air-conditioning
system to carry off the heat it generates in operation.
Dr. John P. Hagen, director of "Project Vanguard," is shown here
with a full-scale cutaway model of the earth satellite designed
by scientists working under his direction at the Naval Research
Laboratory in Washington. D.C. The instrumentation shown inside
includes telemetering equipment which will transmit a radio signal
to earth after satellite has been sent into space. Information is
then relayed to computer.
Heading the staff of the computer installation will be Dr. Paul
Herget, noted astronomer who is director of the Cincinnati Observatory
and a consultant to the Naval Research Laboratory. Dr. Herget is
familiar with IBM equipment, having used the 704 computer's forerunner,
the 701, in a widely applauded planet-tracking operation two years
ago. By carefully computing the orbit of a minor planet named "Athalia,"
which had been discovered by astronomers and subsequently lost again,
Dr. Herget and the 701 pointed to the precise spot in the sky where
"Athalia" ought to be. It was.
To understand how the Vanguard Computing Center will operate,
it is useful to know exactly where it fits into the satellite program
as a whole. Like numerous other International Geophysical Year (IGY)
programs, the satellite experiment is designed for the specific
purpose of expanding scientific knowledge of the earth. Scholars
and scientists in many fields will observe the satellite, gleaning
information from it on such subjects as solar radiation, cosmic
rays, meteors, the earth's gravitational field and atmosphere. The
actual launching of the moon, a task dubbed "Project Vanguard" because
it must precede all other parts of the satellite program, will be
carried out by the U. S. Army, Navy, and Air Force, under general
Navy management. The launching has been made a military responsibility
simply because the military services have had more practice than
anyone else in building and firing rockets.
Three rocket stages with a length of 72 feet and a maximum diameter
of 45 inches are expected to put the man-made moon in its orbit.
The first stage, a Viking-like rocket carrying several tons of liquid
fuel, will push the satellite up to a height of 35 to 40 miles.
The second stage, also a liquid-fueled rocket and probably - like
the first stage - controlled from the ground, will blast upward
to 130 or 140 miles, reaching a speed of more than 10,000 miles
an hour. After the second-stage fuel burns out, the momentum of
the assembly is expected to carry it somewhere between 200 and 300
miles above the earth. The second-stage rocket hull will be jettisoned,
and the third stage will begin to fire.
Now an extremely critical set of maneuvers will take place. They
will not be controllable from the ground, but will depend entirely
on pre-set automatic devices. These devices are counted on to direct
the final rocket on a course roughly parallel with the earth's surface,
and to hold it on that course until it reaches a speed as near as
possible to the desired 17,000-plus miles per hour.

Dr. Paul Herget at the console of the IBM 704 Electronic
Data Processing Machine. He heads the "Project Vanguard"
Computing Center in Washington where this system is being
used to predict and calculate the orbit of the man-made
earth satellite. |
Finally, the satellite will be ejected from the rocket to travel
space on its own. Like the natural moon, it will be held in its
orbit by a compromise of centrifugal force and the earth's gravity.
The shape of the orbit will be determined by the direction and speed
at which it leaves the last rocket. Too great a deviation from the
desired speed and direction will result in the satellite's (1) cutting
down into the top layers of atmosphere, where friction will cause
it to disintegrate in white heat like a meteor; or (2) establishing
an orbit that carries it so far away from the earth as to make effective
observation extremely difficult or virtually impossible.
If all goes as planned, the artificial moon will settle into
an orbit somewhere between these extremes. It will travel in the
same general direction as the earth's rotation, most probably at
an inclination of 30 to 45 degrees to the equator. Thus, it will
be seen to rise in the west and set in the east. It is expected
to circle the earth roughly once everyone and one-half hours. Scientists
assume that, unlike the natural moon, it will meet just enough resistance
from air and other particles to slow it down gradually, until finally
it drops into denser atmosphere and burns up.
Since the satellite's orbit cannot be predicted prior to the
launching, there is no way in which observers can be told now where
to look for it in the sky. The tiny moon may be visible for brief
periods under certain conditions at dawn and dusk, when it reflects
the sun's rays at just the right angle, but this cannot be counted
on as a foolproof way to keep track of the satellite. Some means
must be provided to keep it under continuous observation. This is
where the electronic computer center comes in.
Inside the satellite will be, among other instruments and devices,
a miniature radio transmitter from which will emanate a continuous
signal. This signaling system is named "Minitrack," in reference
to the midget size of the equipment. Its signal will be picked up
by a series of ground Minitrack stations located roughly in a north-south
line extending from the mid-latitude region of the U. S. to the
latitude of Chile in South America. Each station will take several
readings as the satellite passes overhead; the readings will each
consist of a precise placement of the satellite in the sky as measured
from the station, together with an exact time of measurement.
These readings will be relayed from the Minitrack stations to
a communications center in Washington, D. C. From here, the readings
will go by direct teletype to the Vanguard Computing Center.
Immediately upon receipt at the Computing Center, the Minitrack
measurements will be translated into punched-card form. The cards
will then, in most cases, be fed directly into the 704 computer
for a complex series of calculations. Cards can be used effectively
when there is a relatively small amount of input data, as in the
case of the satellite measurements, to be subjected to a large amount
of manipulation in the computer. If the input data were greater
- as in the case of business accounting records, for example - the
punched-card data would be transferred to magnetic tape, which can
be "read" electronically at vastly higher speeds than can cards.
Taking the Minitrack sightings as points along the satellite's
orbit, the computer will, in effect, connect the points with a line
and thus calculate the full orbit. It will continually recalculate
the orbit throughout the life of the satellite. As the midget moon
completes more and more revolutions, and as ever more measurements
are made, the computer's accuracy will steadily increase. Before
long, the calculated orbit will even include perturbations, or "wiggles,"
caused by variations in the earth's gravitational field, attraction
of the natural moon and other heavenly bodies, and other factors-perhaps
including some not now foreseen.

The magnetic core storage unit of the IBM 700 series computer.
This is the "memory" of the machine. Many frames of magnetic
core arrays. consisting of tiny cores strung on copper wires.
provide high-speed storage unit. |
The computer will have other jobs to do besides marking out the
satellite's true orbit. One of the most complex tasks will be that
of calculating the man-made moon's shadow path on the earth's surface,
or, to put it more accurately, the path traced on the surface by
an imaginary vertical line drawn from ground to satellite. The computer
will be able to predict this shadow path in advance. Then, by carrying
its calculations still further, it will be able to work out a useful
- in fact, indispensable - timetable for the benefit of official
visual tracking stations and individual scientific observers participating
in IGY. The computer will tell each of these observation posts exactly
where and when to aim its telescope so that the satellite passes
through the field of vision. Without this precise timetable, telescopic
observers would have small hope of catching the tiny moon. It will
traverse the sky at a rate of one degree, or roughly two diameters
of the natural moon, per second.
These calculations are not easy. While the satellite is in its
orbit, it will be independent of the earth's rotation beneath it.
Each time the little moon completes a circle, the earth will have
rotated 1400 to 1600 equatorial miles to the east. Thus, if the
satellite is launched at an angle of 40 degrees to the equator,
its shadow path after twenty or thirty revolutions will be a curved
line that weaves back and forth between 40 degrees north latitude
and 40 degrees south, crisscrossing itself many times.
If a precise telescope-aiming timetable were worked out by human
computers with paper and pencil, they could never keep pace with
the fast-moving satellite - much less get ahead of it and predict
its course. It will take an electronic computer, capable of such
feats as multiplying or dividing approximately 4700 ten-digit numbers
per second, to keep up with the required pace.
In making its calculations, the computer will rely principally
on a highspeed magnetic core storage, or "memory." This storage
will contain the computer's instructions, now being worked out and
programmed in the computer by Vanguard and IBM experts. When the
various tracking-station data are submitted to the computer, it
will act on the data in accordance with its memorized instructions.
Essentially, the computer's storage function works by means of doughnut-shaped
cores, about the size of pinheads, which are strung on a complex
of wires in such a way that several wires pass through each core.
Combinations of electrical impulses on these wires alter the magnetic
states of the cores. A line of cores, some magnetized and some neutral,
represents a number or other collection of symbols in much the same
way as a combination of dots and dashes stands for a word in Morse
code.
Up to 32,768 of these "words" can be stored in the 704's high-speed
magnetic core memory. Additional "words" can be held in auxiliary
storage by attaching magnetic drum units. The 704 can also control
ten magnetic tape units with a capacity of 900,000 "words" each.
The results of the Vanguard 704's computations will flow from
the machine in three principal forms. Some of the information will
come out in printed form, by means of a direct printer attached
to the 704. Some will be on magnetic tape, for printing later on
a tape-to-print device. Still other information will be presented
in visual form on an ingenious device known as the Cathode-Ray Tube
Output Recorder. This device will picture the computer's calculations
graphically. It will show, for example, the actual shape of the
satellite's orbit as plotted by the 704. It will also show the shape
of the shadow path, or any other aspect of the satellite's travels
that can usefully be displayed in visual form.

The IBM 740 cathode-ray tube output recorder (CRT), a visual
display unit which pictures the output of the 704 Electronic
Data Processing machine in the form of engineering symbols,
words, numbers, or geometrical figures. The orbit of the
earth satellite can be plotted on the screen of the tube
as the information is being computed by the machine. With
this unit, "Project Vanguard" scientists will trace the
course of the satellite over the face of the earth below
the orbit of the device. |
This recorder actually incorporates two cathode-ray tubes. One,
a 21-inch tube, is used for immediate display of information worked
out in the computer. The other, a seven-inch tube, is designed to
work with a 35-mm. camera for recording purposes. This recording
device will be used to advantage in the satellite program. Photographs
of the midget moon's shadow path, together with marked-off arrival
times, will be superimposed on maps of regions having favorable
observing conditions.
In the U. S., people living in the southern half of the country
will have the best chance of seeing the satellite. The angle of
inclination at which it will be launched has not yet been announced,
but a general assumption is that the angle will neighbor 40 degrees.
The 40th parallel runs through Philadelphia in the east and about
150 miles north of San Francisco in the west; thus, moon-watching
conditions will be most probably favorable east, west, or south
of these cities.
Visual observation of the satellite will become increasingly
important as time goes on. Some weeks after the artificial moon
is launched, if it stays in orbit that long, the batteries powering
its Minitrack transmitter will die. From then on, all measurements
will have to be made optically, or by other means that require no
help from the satellite itself. Long before this time, however,
the computer will have reached a fine enough degree of accuracy
in its orbit calculations so that the tiny sphere, though no longer
calling out its own position, will never be lost in the sky as long
as it continues to revolve.
Where will be the profit in this program, aside from the sheer
excitement of it? The profit, scientists hope, will lie in a flood
of new and useful knowledge that can be had from this and other
satellites almost certain to be launched in years to come. Many
observation posts, not directly connected with Project Vanguard,
will be watching the satellite as it speeds around the planet. The
Smithsonian Institution, for example, plans a large-scale moon-watching
operation, as do numerous universities and other scholarly and scientific
bodies throughout the world. Most of them will be aided by the Vanguard
Computing Center.
The satellite's orbit itself will offer much information to observers.
The earth is not a perfect sphere; nor is its mass uniform throughout.
The perturbations of the satellite's orbit, subjected to various
calculations, will add to present knowledge of these irregularities.
Another area of inquiry is the nature of space at the 200-mile-and-up
level. It is supposed to contain tiny meteoric particles that fall
in a continual rain toward the earth, as well as highly rarified
air. The drag effects of these substances will be measurable in
the satellite's orbit, thus offering a clue to their density.
Inside the satellite will be about ten pounds of instruments
(total weight of the sphere: a little over 20 pounds). These instruments
will gather data about the sun's radiation, cosmic rays, and other
phenomena that scientists have not been able to assess accurately
because the earth's atmosphere interferes. Sensitive receiving equipment
on the ground will pick up the data recorded by the space-travelling
instruments.
Though the first man-made satellite has not yet left the ground,
scholars and scientists are already speculating delightedly about
future moons. As the science of rocketry progresses, it is altogether
likely that fuels will be developed to provide more thrust per pound.
At present, it takes a colossal tonnage of propellant to hoist a
20-pound sphere into an orbit; the satellite itself is only a minute
fraction of the vehicle's total weight. As new fuels are developed,
it may be possible to launch larger satellites, capable of carrying
more instruments and gathering more data for science. Whatever is
done in the field in years ahead, however, there is almost certain
to be an electronic computer handling a key phase of the program.
Posted March 24, 2014
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