World’s Biggest Belts
by John Korn Jr.
– the Final Frontier”.
words, uttered by Captain James T. Kirk of the Starship Enterprise,
may be the most familiar reference to man’s fascination with what lies
beyond our atmosphere, but certainly that fascination goes back to the dawn of
man. Since they had no internet or
cable TV for night-time entertainment, early man saw things in the patterns in
the sky. That power of imagination
led to the realization that the patterns moved and eventually repeated.
The list of
astronomers and physicists that followed those early sky-watchers is too great
to discuss. One particular physicist will be the topic of this paper.
of space science research began when native Iowan James Van Allen developed
experiments to study cosmic rays.
September 7, 1914, James Alfred Van Allen was born in Mount Pleasant, Iowa.
He graduated from Mount Pleasant High School in 1931 and in 1935 received
his Bachelor of Science degree from Iowa Wesleyan College in his hometown.
Iowa Wesleyan had a top-notch physics professor named Thomas Poulter and
with Poulter’s help, Van Allen tracked meteors, measured cosmic rays at the
ground level, and conducted a magnetic survey of Mount Pleasant.
went on to study at the University of Iowa, earning his master’s degree in
solid state physics and his PhD in nuclear physics.
He then joined the staff at the Carnegie Institution in Washington, D.C.,
as part of the Department of Terrestrial Magnetism. This
was where Van Allen became very interested in cosmic rays.
World War II intervened and Van Allen’s work shifted to the development of
photoelectric and radio proximity fuses for bombs, rockets and gun-fired
projectiles. A proximity fuse causes
a bomb to detonate at a fixed distance from its target, rather than upon
In 1942 Van
Allen continued his work on proximity fuses at Johns Hopkins University.
This activity included pioneering the development of rugged Geiger tube
instrumentation for flight. He and
his researchers shot shells into the sky and when they had fallen back to earth,
dug them out of the ground with post-hole diggers to see if the vacuum-tube
component had survived the firing. Eventually
they came up with a workable proximity fuse.
The development of this fuse was considered to be one of the great
wartime technological advances made by the Navy.
In addition, Van Allen invented the electronic circuit for the fuse (of
which several million were manufactured), and, with four other scientists
received the patent for the vacuum tube in the fuse.
1942 he entered the Navy, serving as a gunnery officer in the South Pacific.
He actually was tasked with testing the shells and proximity fuses under
combat conditions. For this service
he received four combat stars.
discharged from the Navy in 1946 and returned to his research at Johns Hopkins
in the Applied Physics Laboratory.
It was at this time that he established the High Altitude Research Group
to conduct high-altitude experiments using V-2 rockets captured from the Germans
at the end of the War.
also investigated ultra-violet solar spectroscopy, geomagnetism, and atmospheric
ozone. Van Allen decided a
small sounding rocket was needed for upper atmospheric research which led to the
development of a new missile by the Navy. This
new rocket was called the Aerobee.
note on terminology – a “sounding rocket” is a rocket used for carrying
instruments to where measurements need to be taken. The
term has nautical roots; “to sound” is to throw a weighted line from a ship
into the water to measure the water’s depth).
In 1947 Van
Allen was elected chairman of the V-2 Upper Atmosphere Panel.
In 1949, Van Allen and his colleagues developed the idea for the “Rockoon”.
This inexpensive $750 contraption was a solid-fuel sounding rocket not
ignited on the ground but carried into the upper atmosphere by a balloon.
This allowed the relatively small rocket to reach much higher altitudes
at a fraction of the cost of a V2 launch vehicle.
A decade later Time Magazine reported in a cover story on him that “Van
Allen’s Rockoons could not be fired in his home state for fear that the spent
rockets would strike an Iowan or his house”. Van
Allen had to convince the US Coast Guard to let him fire the Rockoons from an
icebreaker bound for Greenland. The
first Rockoon rose properly to 70,000 feet but the rocket did not fire.
The second Rockoon did the same thing.
Van Allen reasoned that the very cold temperatures at that altitude were
to blame so for the third rocket he heated up cans of concentrated orange juice
from the ship’s galley and bundled them around the Rockoon’s gondola.
That rocket fired.
interesting event took place in 1950 that altered the interaction between man
and space. An English physicist
named Sydney Chapman visited Van Allen and remarked that he would like to meet
other Washington area scientists. Van
Allen contacted eight or ten of the top scientists in the area and arranged a
meeting in the living room of his modest Bethesda, Maryland home.
He later referred to it as “a pedigreed bull session”.
Talk turned to geophysics and the two “International Polar Years”
which took place in 1882 and 1932 in which the world’s leading nations studied
the earth’s Arctic and Antarctic regions.
The time was ripe for a world-wide geophysical year, what with the recent
advances in rocket and instrumentation technologies.
The group was enthusiastic about this idea and the idea spread around the
world to other scientists. From this
meeting the group, led by Lloyd Berkner, made a proposal to the International
Council of Scientific Unions that an International Geophysical Year or IGY be
planned for 1957-1958, during the maximum solar activity.
This IGY, which ultimately involved scientists from sixty-six countries,
was enough to stimulate the US Government to promise to develop earth satellites
as research tools. The Soviets
countered by developing and rushing their Sputnik
satellite into orbit on October 4, 1957. Embarrassed
by the surprisingly fast success of Sputnik,
the Americans frantically finished their first satellite, Explorer 1 and launched it four months later.
The Space Race was on! This
all occurred as a result of that meeting and therefore, it can be said that the
Space Race as we know it, began in James Van Allen’s living room.
retrospect, it is believed that had the U.S. Government acted sooner on Van
Allen’s recommendation as to which branch of the armed services should launch Explorer
1 – Van Allen favored the Army rocket – this country would have been the
first nation in space. Said Van
Allen: “We could have put a satellite in orbit as early as September of 1956
– we had the know-how”.
months in 1957, as part of the International Geophysical Year, Van Allen sailed
from the Arctic to the Antarctic taking cosmic ray measurements with Rockoons.
Today a satellite in orbit takes more data in a few minutes than Van
Allen did in his five month voyage. Yet
Van Allen’s vision for the low cost Rockoon as an alternative to the much more
expensive Aerobee or V2 allowed him
and his students to launch more than 700 Rockoons from 1952 to 1957.
Off the coast of Greenland, Van Allen’s Rockoons recorded an intense
concentration of cosmic rays at an altitude of thirty miles, a clue to the
existence of the yet-to-be-discovered radiation belts.
James Van Allen is best known for his discovery of the earth’s radiation belts which bear his name. This discovery was important enough to the scientific community to land him on the cover of Time Magazine on the May 4, 1959 issue. As the world prepared to send humans into space, it was a critically important discovery – sending men unknowingly into a relatively harsh environment of radiation would be a tragedy. Radiation also destroys electronic devices so understanding the belts was and is an important discipline with regard to satellites.
The Van Allen Belts are two doughnut-shaped belts of radioactive particles from the sun, trapped by the earth’s magnetic field. The configuration of this doughnut shape is based on the magnetic poles of the earth. If you were to fly away from the earth from either pole you would not encounter the radiation and if you flew straight up from the equator you would encounter the thickest parts of the belts.
Discovered in 1958 with
instruments aboard the Explorer 1 spacecraft,
the Van Allen Radiation Belts have long intrigued scientists. The inner belt,
stretching from about 1,000 to 8,000 miles above Earth's surface, is fairly
stable. However, the outer ring, spanning 12,000 to 25,000 miles, can swell up
to 100 times its usual size during solar storms, engulfing communications and
research satellites, bathing them in harmful radiation. Further complicating
matters, the outer belt does not always respond in the same way to solar storms.
Sometimes it swells; sometimes it shrinks - an event caused when electrons in
the outer loop either drop into the atmosphere or escape into space.
normal conditions the communications satellites in geosynchronous orbit at
26,199 miles are just out of the belt.
Considering the important part satellites play in our lives today, a good
understanding of the belts continues to warrant research.
on August 30, 2012, a pair of satellites called the Radiation Belt Storm Probes
were launched to continue research on the Van Allen Belts.
They were soon renamed the Van Allen Probes.
Your essayist cannot find evidence as to why they were not so-named in
the first place.
September, scientists with the newly launched probes got permission to turn on
one of their instruments after only three days in space instead of waiting for
weeks, as planned. They wanted to turn on the Relativistic Electron Proton
Telescope (REPT) so that its observations would overlap with another, similar
mission, that was soon going to de-orbit and re-enter Earth’s atmosphere.
They were soon very glad they did, because something happened
that no one had ever seen before. A
previously unknown third radiation belt formed in the Van Allen Radiation Belts.
The scientists watched – in disbelief – while their data showed the extra
belt forming, then suddenly disappear four weeks later, like it had been cut
away with a knife. They have not yet seen a recurrence of a third belt.
we thought our instruments weren’t working correctly,” said Dan Baker, a
member of the Van Allen Probes team from the University of Colorado at Boulder,
“but we quickly realized we were seeing a real phenomenon.”
happened is that shortly before REPT was turned on, solar activity on the Sun
had sent energy toward Earth that caused the outer radiation belt to swell. The
energetic particles then settled into a new configuration, showing an extra,
third belt extending out into space.
of the belts over the years have shown they are dynamic and mysterious. However,
this type of dynamic three-belt structure was never seen, or even considered,
Energetic Particle, Composition, and Thermal Plasma (ECT) suite of instruments
on board the probes were designed to help understand how populations of
electrons moving at nearly the speed of light and penetrating ions in space form
or change in response to variable inputs of energy from the Sun.
what the team has learned is re-writing the textbooks of what is known about the
Van Allen belts.
events we’ve recorded are extraordinary and are already allowing us to refine
and confirm our theories of belt dynamics in a way that will lead to
predictability of their behavior,” said astrophysicst Harlan Spence, principal
investigator for the ECT, “which is important for understanding space weather
and ultimately for the safety of astronauts and spacecraft that operate within
such a hazardous region of geospace.”
At a press
briefing, the team was asked why this third ring had never been observed before.
never had the capability before to see something like this”, said Nicky Fox,
Van Allen Probes deputy project scientist. “The fact that we had such an
amazing discovery within days of turning on the instruments shows we still have
mysteries to discover and explain. What the Van Allen Probes have shown is that
the advances in technology and detection made by NASA have already had an almost immediate impact on basic science.”
philosopher Yogi Bera once said, you can observe a lot just by looking. This
shows that when you open new eyes on the Universe you can invariably find new
more about this and understanding more about the belts is important for having
better models and being able to predict the lifetimes of spacecraft,” said
research continues. A smaller
version of the instrument on the Van Allen Probes has won a coveted spot aboard
an upcoming NASA-sponsored Cubesat mission - the perfect platform for this
pint-size, solid-state telescope.
just 3.3 pounds, the Compact Relativistic Electron and Proton Telescope (CREPT)
will "augment the science of a major flagship mission" and demonstrate
the effectiveness of two new technologies that make the instrument four times
faster than its 30-pound sibling at gathering and processing data.
solid-state telescope, which the team is developing under NASA's Low-Cost Access
to Space (LCAS) program, will measure energetic electrons and protons in the Van
Allen Belts. CREPT measurements will give scientists a better understanding of
the physics of how the radiation belts lose electrons by a process known as
$1.5-million LCAS award, this team will spend the next two years building CREPT.
In year three, they plan to fly the telescope on a three-unit Cubesat.
CREPT will be able to study electron growth and decay from a low-altitude
polar orbit - an observing location that augments the science now being
performed by REPT, which is flying in an equatorial orbit at high altitudes.
Allen once said that finding the radiation belts around Earth was “the most
exhilarating professional accomplishment I’ve been lucky enough to make.”
He went on to say “next in order would probably be the encounter with
Saturn. I had
apparatus on Pioneer 11, which encountered Saturn in 1979.
It was not known whether Saturn had radiation belts before we got there.
Then we arrived (slide 4) and we found it did have belts – and we made
a really good survey of them. In the
meantime, we had encountered Jupiter. (slide
5) This was also an exciting
occasion, but perhaps less so than the case of Saturn.
With Jupiter, we had radio evidence of radiation belts before the arrival
of Pioneer 10. Still, in terms of
professional satisfaction, this ranks right up there with the other two
in Dr. Van Allen and the department he chaired for so many years comes from my
good fortune to work there from 1979 to 1983.
It was during this time that the building known as “The Physics
Building” was renamed “Van Allen Hall” and as a member of the staff, I was
invited to attend the dedication ceremony. The
first three years I was a technician while enrolled in the College of
Engineering; upon graduation in 1982 I was promoted to Engineer.
The project I worked on was a Very Low Frequency Plasma Wave instrument,
one of many instruments that went to Jupiter aboard the NASA spacecraft Galileo.
this case is charged particles which exist in space and their density varies in
a repeatable fashion, hence the term “plasma wave”.
Plasma in space is matter which has reached an elevated physical energy
state. For example, water in its
lowest energy state is a solid (ice). Apply
energy to ice and you get the liquid form, the next energy state.
Apply energy to water and you get steam, and if you could apply energy
under the right conditions to steam, you would get a plasma.
The aurora borealis or northern lights is an example of a plasma.
The glowing plume of a burning candle is another example of a plasma.
My final duty for Galileo was environmental testing for a month at the Jet Propulsion Laboratory in Pasadena, California. The Galileo mission nearly didn’t happen. It was scheduled to launch in 1986 on the next space shuttle mission after the shuttle Challenger exploded in January of that year. There were no more shuttle flights until late 1989 and by that time the planets were in a very different alignment. The NASA engineers had to send Galileo out and a few months later slingshot it around Earth to get it to Jupiter where, rather than make a fly-by like most satellites, it went into orbit and remained there for the lifetime of the mission.
Van Allen is best known for discovering Earth’s radiation belts, a
lesser-known but very admirable accomplishment is the kind of educator he was.
Many professors choose to teach the minimum required courses so as to focus on
their area of research. Dr.
Van Allen continued to teach many classes throughout his career and enjoyed
getting his students involved in his research.
And he taught with steady kindness and gentle patience.
Evelyn Robison, his program assistant for several decades, said, “I
have never seen his good disposition vary one single day.
It’s always tops.”
of Van Allen’s fondness of teaching came shortly after he discovered the 11th
moon of Saturn. Rather than call for
a press conference, Van Allen casually announced his discovery to a general
astronomy course filled largely with freshmen students.
One of the students, a newspaper reporter for The
Daily Iowan, the university’s paper, recognized the scoop and quickly put
it out on the wire services where it was reported around the world.
Van Allen said with a shrug, “It’s minor, not exactly a barn-burner,
but another step in finding out how Saturn evolved.”
basic astronomy course was not a one-time thing.
Dr. Van Allen chose to do this regularly throughout his career.
The hundreds of students who took this course were encouraged to
interrupt him at any time with questions.
for teaching was based in his passion for learning.
At a ceremony in the fall of 1984 to initiate the school year, Dr. Van
Allen addressed the students and faculty present and had this to say:
morning I wake to the realization that there is something I would like to
understand but do not. A good day is
one during which I manage to inch forward a little in understanding and
It is a
matter of experience that there is always someone who knows more about any
specific matter than I do. But I am not discouraged by the vastness of my own
ignorance – nor should you be for the following simple reason:
each of us has a greater or lesser capability for combining what we do
know to formulate a concept or develop a course of action.
Therein lies the creativity and the uniqueness of the individual.
And the central purpose of education is to enrich and heighten that
Allen was very much a family man – he met his wife in Washington when she
backed her car into his front bumper. Minutes
later he realized that they both worked at Johns Hopkins when he saw her enter
the building. Although her degree
from Mount Holyoke was in English Literature, her job at Johns Hopkins was as a
mathematician. They later married
and had 5 children, Cynthia, Margot, Sarah, Thomas, and Peter.
Dr. Van Allen also had a brother who was a professor at the University of
Iowa’s College of Medicine.
Allen died on August 9, 2006 at age 91. His
impact on space research continues around the world with projects like the Van
Allen Probes and the upcoming CREPT spacecraft.
Work at the Department of Physics and Astronomy at the University of Iowa
has not slowed down. In addition to
the 63 instruments and spacecraft designed and built at Iowa which are no longer
operational or in existence, 13 are currently in use, still providing scientific
data. This includes Voyager 1 and 2,
launched in 1977. Two instruments
are currently being built, slated for launch in 2014, and a third is planned for
furthest reaching of James Van Allen’s legacies is the continuation of
unmanned space exploration. He was a
very strong proponent of satellites versus sending people into space, saying
that “dollar for dollar, we can get hundreds of times more science from
unmanned space vehicles than sending people up there.”
In a speech before The American Geophysical Union, he questioned the
advisability of spending huge sums of money on a manned space station, calling
it a “massive misdirection of resources.”
continual advances in electronics and shrinking budgets we can expect to see
more and more science come from unmanned spacecraft.
It’s fortunate that the trend with electronics is that they rapidly get
better, smaller and cheaper because funding will certainly continue to wane.
continue to gain knowledge about what makes up our universe and how it evolved,
and we have James Van Allen to thank for the origins of this branch of science.