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"Satellites have radar on board that crea-
tes images by sending out its own radia-
tion (electromagnetic waves), and which
detects the radiation that is reflected
back. But we must interpret this image.
For example, we want to distinguish
between different types of ice: ice that
has been around for a long time, which
is called multi-year ice, and ice that is
only one season old. To do this, we create
algorithms. These analytical methods
make it possible for us to categorize the
different forms of ice in satellite images.
From this we can create a map where, for
example, each type is given own colour
code," says Eltoft.
As algorithms become more advanced,
more information can be read from each
satellite image. In this way we increase
our knowledge of sea ice, particularly
about what represents normal variation
and what are unsettling changes. The
University works with the Norwegian
Polar Institute and NORUT, the North-
ern Research Institute, to categorize sea
ice from the sea. At the same time, the
Norwegian Polar Institute measures sea
ice from a boat.
"Field research can only measure a tiny
proportion of the ice. With satellites, we
can monitor the entire Arctic Ocean. But
it is important to conduct field work on
the ice, so that our satellite measurements
are compared to reality," Eltoft adds.
May reduce risk of accidents
The University of Tromsø is not only
involved in monitoring and mapping of
areas close to Norway. Along with NOR-
UT, Kongsberg Satellite Services (KSAT)
and several other research groups, the
university is involved in monitoring rain
forests in Tanzania.
"Our work here at home has enabled us
to build a great deal of expertise, particu-
larly with respect to radar. The idea is that
over time, we can build up a knowledge
base in Tanzania, so that they can carry
out satellite monitoring on their own,"
Eltoft says.
Earth observation satellites can also be
used to monitor more than just ice and
forests. Satellite information can be used
to map vegetation and land use; measure
wave height, wind and currents in the
ocean; measure sea temperature; and
monitor landslide-prone areas.
The satellites can also be used to reduce
the risk of accidents. For example, if an
iceberg is drifting towards an oil instal-
lation, it can be detected in time and a
warning sent out. The satellites can also
act like guides for ship traffic, and indi-
cate where sea ice is thick and where it is
thin. This can influence the ship's route
selection.
"We have the ability to monitor many
areas that can pose a threat to people,
whether it is cliffs that are in danger of
tumbling down, or larger oil spills in the
sea," Eltoft says..
Facts about Earth
observation satellites:
• Earth observation satellites travel at
about 600 - 800 km above the surface of
the planet. They take about 100 minutes
per full orbit and thus complete approxi-
mately 14 full orbits per day.
• Since these satellites follow a polar orbit
(orbits that cross the equator), it is useful
to locate downloading stations the near
the poles. The Tromsø company Kongs-
berg Satellite Services (KSAT) maintains
these kinds of stations in Svalbard,
Tromsø, and at the Troll, the Norwegian
Antarctic base.
• Satellites have sensors that can measure
reflected electromagnetic radiation
(mainly solar radiation) and radiation
sent out from the soil surface. Therefore,
these sensors are only used to collect data
during the daytime, when it is light.
• Other sensors in the satellites create their
own radiation for use (such as lasers and
radar). Radar systems that operate in the
microwave region (wavelengths of about
0.1 to 30 cm), function independently of
weather and lighting conditions, and are
therefore suitable for monitoring polar
regions.
University of Tromsø –
Labyrint E/11
•••
17
Satellite orbits
Image of the ocean and sea ice off Svalbard