Cryosat A Satellite On An Icy Mission
- View SourceFriedrichshafen - Nov 11, 2003
CryoSat, the ice research satellite developed and built by EADS Astrium
for the European Space Agency ESA, is nearing completion at a fast pace.
The mechanical integration and the functional tests are in full swing at
the Friedrichshafen based satellite centre.
In spring 2004, CryoSat is to be transported to Munich for conducting
tests under space conditions. Following successful testing, there is
nothing to prevent its launch from the Plesetsk Cosmodrome in Russia. The
launch is scheduled in autumn 2004 on board a Rockot launcher.
CryoSat is the next European environmental and climate satellite. Placed
in a polar orbit it will measure changes in the thickness of ice sheets
and polar ocean sea-ice cover for at least three years with unprecedented
accuracy. The satellite will provide climate researchers with previously
unavailable data from these uninhabited regions. The industrial contract
amounts to some 70 million euros.
The evidence of climate warming can be ignored no longer. As reported by
the Intergovernmental Panel on Climate Change (an international board of
climate experts), the average global surface temperature rose by 0.6
degrees in the 20th century. Climate data indicate that the 20th century
was the warmest in the last thousand years.
At the same time, since 1750, the concentration of greenhouse gases in
the atmosphere, such as carbon dioxide and methane, has grown by 30 and
150 percent respectively as a result of human activities.
Using the models available at the moment, it is only partially possible
to predict how these developments affect the climate. The predictions
waver between a global warming of between 1.4 to 5.8 degrees Centigrade
in the next hundred years. As a consequence, experts expect some polar
ice and glaciers to thaw. This could result in the water level of the
oceans rising by up to a metre.
Polar ice as a climate factor
The presence of ice at the poles plays a central role for the global
climate. Despite being thousands of kilometres away from the most
inhabited areas, this ice has a profound effect on the climate in Europe,
Asia and the Americas.
Three aspects are most important:
Snow and ice reflect sunlight extremely well
A sea-ice cover insulates the water underneath and
Large amounts of thawing ice affect the large-scale ocean currents.
Polar ice reflects a large portion of the sunlight, and the amount of the
absorbed and reflected light is balanced with the climate. If the polar
ice begins to melt, less sunlight is reflected and therefore the polar
region warms up. Consequently, more ice begins to melt and the reflective
capabilities are thus further reduced. Due to this positive feedback
effect, a self-accelerating warming ensues.
In the night, open water radiates a large heat output of about 90 Watts
per square metre. A snow-covered sea-ice slab floating upon the ocean
beneath has a negative effect on this. To a certain extent, it acts as a
thermal blanket and therefore plays a significant part in regulating the
heat balance of the Earth. This effect is reduced as soon as the ice
thins or decreases in extent.
Ocean currents have a special influence on the climate. They act as heat
pumps, as they disseminate the energy stored in the oceans around the
entire globe. The most well known example is the Gulf Stream, which
transports warm water from the tropics diagonally over the Atlantic to
North Europe and provides Great Britain with a mild climate and ice-free
ports up to North Scandinavia.
If the ice sheets and the outer sea ice cover melt, the relatively larger
quantities of fresh water could disrupt or even change these ocean
currents � with unforeseeable effects for the climate.
CryoSat � the first mission of the "Living Planet" Programme
A large part of the uncertainties in the climate models of today is due
to the fact that there is a lack of precise measurements of the polar ice
and its development. Experts conjecture that the sea ice has receded by
10 to 15 percent since 1950. The thickness of the Arctic ice is reported
to have reduced by 40 percent in the last few decades. These statements,
however, are extremely uncertain due to the lack of widespread
information on sea-ice thickness.
CryoSat is to fill in this gap in climate research. The satellite will
start as the first Earth Explorer Mission of ESA�s "Living Planet"
programme initiated in 1998. The aim of this research programme is to
give answers to the urgent scientific questions.
The "Living Planet" programme is pursuing two strategies: First, the so
called Core Explorer Missions which are relatively complex and cost
intensive Earth observation missions for scientific purposes and second,
the Opportunity Missions using mature technology thus enabling fast and
low cost project implementation.
CryoSat will be the first Earth Explorer Opportunity Mission. In July
1998, ESA called upon all scientists from its member countries for
mission proposals for this programme.
Researchers from University College London and other collaborating
institutes, were supported by employees of Astrium in proposing CryoSat.
Astrium�s early commitment in this mission ensuring low cost feasibility
by simple and reliable technical concepts as early as in the first phase
was unusual. In April 1999, the ESA programme committee selected CryoSat
from a total of 27 submitted projects.
Radar altimeter measures ice thickness
CryoSat will circle the Earth in a polar orbit 720 km high. From there,
its radar will measure the thickness and circumference of the polar ice
sheets and sea-ice cover. Previous radar satellites, such as the European
ERS 1 and 2 or Envisat, are only equipped with a single antenna. With
this, they can deliver information about uniform ice surfaces with a
CryoSat, on the other hand, has two antennas. Similar to the way in which
humans, with two eyes, can see spatially, CryoSat�s double radar will be
able to scan the upper surface very precisely. Experts call this radar
interferometry. With this system, an average accuracy of one to three
centimetres can be reached. Thus it can also collect data on
inhomogeneous ice structures in the polar seas and glaciers or ice sheets
with very steep walls.
In order for this extreme precision of measurement to be attained, the
orbiting altitude of the satellite must be constantly known. To determine
this to within a few centimetres, ground stations emit signals, which are
received and processed by an instrument named DORIS. The information
about altitude, which is thereby produced, is then conveyed via the
normal data stream to the ground station.
CryoSat�s outer side also sports a laser retro reflector. Similar to
cats� eyes in warning posts on the edge of a road, it reflects a ray of
light. If one were to send a laser beam to CryoSat from a ground station
and receive the reflected signal from the satellite, one would be able to
determine the height of the satellite from the transit time.
CryoSat�s radar altimeter functions regardless of daylight and can also
penetrate clouds. Therefore, it is particularly suited to the research of
the large polar ice sheets, which rise up to 4000 metres above sea level
and which are often covered by clouds. The data from the CryoSat mission
are to deliver information about the rate of change of these ice sheets.
Working with a tight budget
EADS Astrium is the prime contractor for CryoSat and thus responsible for
a consortium of 31 companies. EADS Astrium itself is building the
satellite platform and will integrate all instruments. Ultimately,
Astrium is responsible for the reliability of the whole satellite to ESA.
From the beginning, the special challenge of the CryoSat project for the
EADS Astrium�s engineers was the apparently contradictory requirements of
high reliability, fast realisation and a low cost.
In the meantime, the satellite architecture of disarming simplicity and
the proven hardware components supplied by the subcontractors have shown
that the programme can be implemented as scheduled. The close partnership
between scientists, ESA and the industrial consortium enables a lean
management and, at the same time, more transparency and faster reaction
time during the development and construction phases.
Lidar Instruments Test Icesat
Madison - Nov 05, 2003
Since October 8, UW�Madison's lidar group has helped NASA test its
ICEsat, the Ice, Cloud and land Elevation Satellite that is studying
changes in polar ice thickness and extent. UW's High Spectral Resolution
Lidar measures the same atmospheric quantities measured by the Geoscience
Laser Altimeter System (GLAS) on the satellite and when ICEsat is
directly overhead about every eight days, the two laser beams can meet to
calibrate the GLAS. The UW instrument operates at the same wavelength as
The two instruments both measure the heights of clouds and aerosols, such
as haze and particles in smoke, in the atmosphere from precise
measurements of the travel time of the laser pulses and, in the
satellite's case, calculated against its orbit and instrument
Both instruments are used in climate studies; the UW lidar is used
particularly to finely tune numerical models of climate and weather,
leading to increasingly better weather forecasts and a better
understanding of Earth's climate.
Calibration tests are dependent on the weather to work well. Thick clouds
keep the beams from meeting. The scientists hope for cirrus clouds or
haze for the maximum effect, and best test�something we can see through,
but that gives a nice signal.
NASA's Goddard Space Flight Center tentatively plans to test the GLAS
this Friday afternoon, November 7. If the laser being tested is still on
in mid-November�it may be turned off by then�the satellite will pass
almost directly over Madison on the evening of November 11. Times will be
known the day of the pass. If the weather is right, the UW lidar will be
seen as a green beam and the satellite as a green flash, as captured in
the video on the UW Lidar Web site.
The UW lidar program has been developing lidar instruments since about
1965, under the leadership of Edwin Eloranta, a scientist in the
Department of Atmospheric and Oceanic Sciences. The researchers and
engineers working with him are employed by the Space Science and
Engineering Center (SSEC). Both groups are housed in the Atmospheric,
Oceanic and Space Sciences Building, which also houses some research
centers in the Institute for Environmental Studies.
The Arctic High Spectral Resolution Lidar will take measurements in the
Arctic ice near Barrow, Alaska starting in 2005. The lidar is being
tested in the top story of the building, beamed through a skylight.
Images like the one below are now available on the Web where you can see
how the lidar viewed the atmosphere on any day since the beginning of
DigitalGlobe Acquires eMap International
Longmont - Nov 04, 2003
DigitalGlobe announced it has completed definitive negotiations to
acquire eMap International (eMap), a Reddick, Fla. Based geo-spatial
consulting practice specializing in geospatial planning, design and
integration. EMap International will become a wholly owned subsidiary of
DigitalGlobe with David Nale, founder, certified photogrammetrist,
mapping scientist and professional land surveyor, serving as president.
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