By Laura Zajac
A mystical stillness spreads over the coast of Norway as the sun
slides slowly into the sea. Shadows lengthen, crevices seem to deepen,
and scattered caves appear. Gull cries echo through the fjords.
Earlier today, fishing boats dotted the waters, trolling for the
day's catch. But now the boats are docked by the villages, scattered
handfuls of cottages clinging to narrow stretches of beach.
The evening mist creeps up the rocks; the damp smells of salt and
fog fill the air. Folktales tell of trolls in these cliffs: Huge
creatures with long crooked noses and a fear of sunlight.
The darkness rises up the cliff-faces, but still the midnight sky
glows muted gold. And high, high above the cliffs, just where the
dying sunlight meets the blue of dusk, are the clouds. Silvery blue,
wispy and mysterious — nocturnal clouds frozen high above the
fjords. 
These noctilucent, or "night shining" clouds were first sighted
100 years ago. They have been observed more frequently in recent
years, an increase that may be due to a pollution-induced change
in our atmosphere. No one knows. "They could be from methane released
into the air," said Dirk Padfield, a Penn State student working
with electrical engineering professors Charles Croskey and John
Mitchell to study these clouds.
The clouds are found near the mesopause, the highest region of
the mesosphere, 52 miles above the ground. "Turns out the very coldest
temperatures on Earth occur at the mesopause," explained Mitchell.
(Summer temperatures of -260 degrees F have been measured.) But
the clouds are only visible at night and in the far north. That
we can see them at all is due to the curvature of the Earth. As
the sun drops behind the horizon, its light, blocked by the Earth,
still travels over our heads through the upper atmosphere. The clusters
of ice in the mesosphere catch the light and reflect it, causing
the event we call noctilucent clouds.
Their location poses a problem for scientists. "Balloons can't
go that high, and satellites can't go that low," explained Padfield.
The only way to study them directly is to launch a rocket into the
middle of one. The study Padfield, Croskey, and Mitchell are working
on did just that. Funded by NASA, the project brought scientists
from Germany, Austria, Sweden, and the United States to Andøya,
or Duck Island, in northern Norway. Each scientist built several
probes to be part of the payload of the rocket.
Padfield's main job was to make sure the three Penn State probes
worked, and to test them for possible interference with the other
probes on the rocket. His other task was simply to learn as much
he could about the project.
A double major in electrical engineering and international studies,
Padfield had worked for a year in Israel before coming to college,
and studied language and religion in Egypt during his sophomore
year. He knows three languages. Born in Alaska, he spent the next
12 years of his life on the same coast of Norway that he returned
to this summer. It was here that his analytical mind and scientific
aptitude first showed themselves. "When I was a kid, I had a notebook,
and I would write the times tables in it. I went all the way up
to 2000, just for fun; I always really liked math," said Padfield.
"Since middle school I've known I wanted to be an electrical engineer;
that hasn't changed, and I just enjoy it more and more as I go through."
His interest led him to seek out Mitchell at Penn State. "Dirk contacted
me through e-mail from Israel," explained Mitchell. He chuckled.
"He's the only student I advised before he became a student."
So when Padfield approached his adviser last spring asking to do
research, Mitchell didn't hesitate to bring him into the rocket
project. Padfield's fluent Norwegian was an unforeseen benefit.
"What size are the particles? Are they charged or neutral?" By
learning the answers to these questions, Mitchell said, "we can
better understand noctilucent clouds." The Penn State probes were
designed to detect the electrical charge of the ice particles. Padfield
described the first probe, called a Gerdien condenser, as "a bucket
with a large whole in the bottom and a little metal cylinder in
the middle." The "bucket" was set to zero voltage. The inner metal
cylinder had a constantly changing voltage that swept from very
negative to slightly positive. As the rocket shot through the cloud,
charged ice particles moved through the bucket. Since "opposites
attract," positively charged ice particles were attracted to and
struck the negatively charged cylinder. As the cylinder became less
negative, large particles passed by but small particles were still
mobile enough to be attracted. Negative particles struck the cylinder
only when the voltage was positive. A sensor in the probe recorded
all these hits, and sent the information back to land via radio
signals.
By combining the information transmitted back from the Gerdien
condenser and the other two probes, the researchers will also be
able to estimate the size and density of the ice particles. Padfield
explains, "If we can understand the charges and density of the particles,
and compare our measurements with those from the other probes on
the rocket, then we can have a better understanding of the clouds
and where they came from. We can know if the clouds are harmful,
if they're caused by pollution, their relation to global warming,
and if they're detrimental to the environment."
In May of 1999, the scientists involved in the project gathered
at NASA's research base in Wallops Island, Virginia. There the rocket
was "basically beaten-up," said Padfield, to simulate possible flight
conditions. "They'd shake it to make sure it wouldn't fall apart.
They'd compress it, and test it again. Then they checked to make
sure all the screws were still in." Afterwards it was taken apart
and shipped to Norway.
On Andøya, Padfield and the other researchers reassembled
the rocket and retested the probes. Then everyone settled down to
await the clouds.
Noctilucent clouds can only be seen from a distance. The launching
party could not just look up and aim the rocket at a cloud; lidar
and radar were used to pinpoint the cloud's location.
Once the target cloud was identified and the wind was blowing the
right way, the rocket was readied for launch. "It really overwhelms
you, overwhelms your senses," explained Padfield. "It ignites and
the whole thing just blows up underneath. There are big flames and
a lot of smoke — it's really loud!" Radar tracked the rocket
on its steep path through the sky. After three minutes, the pointed
cone of the rocket popped off, exposing the probes. The sensors
picked up information for the 10 seconds it took the rocket to pass
through the cloud. After peaking at 73 miles above the ground, the
rocket rotated and, pulled by gravity, plunged toward Earth, passing
back through the cloud and splashing down into the sea. The payload
would remain at the bottom of the sea, but the mission was a success.
Padfield is now developing a computer program to interpret the
signals sent back from the probes. "I learned what research is,"
he said of his experience. "It was humbling. In research, the more
you learn, the more you understand how much more there is to learn."
Dirk Padfield received a B.S. in electrical engineering and
a B.A. in international studies in May 2000, with honors in electrical
engineering, from the College of Engineering and the Schreyer Honors
College. In May he won an NSF Graduate Research Fellowship. His
advisers are John Mitchell, Ph.D., 129 Electrical Engineering East,
University Park, PA 16802; 814-863-2788; jdm4@psu.edu;
and Charles Croskey, Ph.D., 303 Electrical Engineering East; 865-2357;
CCroskey@psu.edu. The project
was funded by NASA. Padfield's participation was funded by NASA,
a Heather L. Rayle Summer Scholarship, and a Schreyer Ambassador
Award. Writer Laura Zajac graduated in May 2000 with a B.S. and
honors in biobehavioral health.
