EVENTS, ADVANCES, AND NEWS
■ BY JEFF ECKERT
FOOLING AROUND WITH
PHOTO COURTES Y OF THE HAARP IONOSPHERIC OBSERVATORY.
■ The HAARP array includes 180
antennas spread out over 33 acres.
If you take Interstate A1 out of
Anchorage, AK, and head a couple
hundred miles to the northeast, you
will encounter the town of Gakona,
which is just a stone’s throw from the
Wrangell Saint Elias National Park.
Even though the population was only
215 when the last census was taken, it
is a pretty interesting place, being
home to the High Frequency Active
Auroral Research Program (HAARP,
Jointly managed by the Air Force
Research Laboratory and the Office of
Naval Research, HAARP is scheduled
to come fully online this year, and it
has two main purposes. First of all, it
has a suite of scientific instruments
(receivers, magnetometers, radars,
etc.) that allow researchers to perform
passive observations of natural auroral
activity to better understand the phenomenon. Second, one can fire up the
ionospheric research instrument (IRI),
which is a high-power HF transmitter
system used to stimulate small areas of
the ionosphere at an altitude between
100 and 350 km. The IRI will stir up a
volume of a few hundred meters by a
few tens of kilometers in diameter,
allowing for various scientific studies.
As of this writing, only 48
antennas are operational, and the
transmitter can generate just 960 kW
8 February 2007
over a frequency range of 2.8 to 10
MHz. However, when complete, it will
be able to pump about 3,600 k W into
the full arsenal of 180 antennas.
Observers on the ground won’t be
seeing any artificial aurora, though, as
the signal strength in the target area is
less than 3 W per square centimeter,
which is tens of thousands times less
than what the Sun delivers.
As a sideline, HAARP will be
experimenting with extremely low
frequency (ELF) signal generation
techniques with an eye toward things
like submarine communications. The
facility has no regular visiting hours,
but you can take a virtual tour at www.
PHOTO COURTES Y OF OHIO S TATE UNIVERSI T Y.
■ Radar signal of subglacial Greenland
topography obtained by GISMO.
million years, and existing radar systems
are not all that good at mapping it out;
they can only generate two-dimensional profiles over very narrow paths.
However, some scientists at Ohio
www.osu.edu) have devised the
Global Ice Sheet Mapping Orbiter
(GISMO), a system that uses multiple
steerable antennas mounted on an
airplane to obtain three-dimensional
images over a mile-wide strip, at depths
1.2 miles beneath the ice surface.
The system uses vertical and
horizontal radar elements to generate
an interference pattern, and computer
techniques are under development
that will increase the radar’s ability to
use that pattern to cancel out
the effects of surface ice. The first
experiment involved peeking under
Greenland’s ice and produced the
image shown. Although the image isn’t
exactly equivalent to a good topo map
yet, the left half of the image does
reveal the vertical layers of ice from
the surface down to the base (white
line, center), and the right half shows a
horizontal view of the topography.
As signal processing techniques
are improved, the images should get
better and become useful for monitoring the effects of climate change on
the ice and water beneath it. It is
projected that the concept could one
day operate from a satellite to study
more of the world or even other
planets. The next trip over Greenland
is scheduled for April, so stay tuned.
It is known that the land beneath the
Earth’s ice sheets — which make up
about 15 percent of the planet — can
run the gamut from areas that have
been scraped flat by moving ice to
mountainous terrain and possibly
lakes and rivers. But it has been very
difficult to study the subglacial
surface, because a lot of it has been
covered with ice for close to three
Late last year, scientists at IBM
www.ibm.com), Macronix (www.
mxic.com.tw), and Qimonda (www.
qimonda.com) announced some joint
research that resulted in a new type of
memory, dubbed “phase-change.”