CryoSat - A Satellite on an Icy Mission
ILA/Berlin, Friedrichshafen, 10 May 2004
CryoSat, the ice research satellite developed and built by EADS Astrium for the European Space Agency ESA, is rapidly nearing completion. Full CryoSat integration has been completed in the Friedrichshafen-based satellite centre. Final tests are currently underway. Mid June, the satellite will be prepared for transportation to Munich where tests will be carried out under space conditions. After the first test phase, the satellite will be disassembled to install the last few electronics units. Then, the final environmental tests will take place. Following the successful completion of these tests, the spacecraft will be prepared for launch from the Plesetsk Cosmodrome in Russia. Launch is scheduled for autumn 2004 on board a Rockot launcher provided through Eurockot, an associate company of EADS.
CryoSat is the latest European environmental and climate satellite. When placed in a polar orbit it will measure changes in the thickness of ice sheets and polar ocean sea-ice cover with unprecedented accuracy for more than three years. The satellite will provide climate researchers with data previously unavailable from these uninhabited regions. The industrial contract is valued at some 70 million euros.
The evidence of climate warming can no longer be ignored. 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 indicates 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 vary between 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 in 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
* Sea-ice cover insulates the water underneath
* Large amounts of thawing ice affect the large-scale ocean currents.
Polar ice reflects a large proportion of the sunlight and the the absorbed and reflected light balance each other out. As the polar ice melts, less sunlight is reflected and so the polar region warms up. Consequently, more ice begins to melt and the reflective capabilities are thus further reduced. As a result a self-accelerating, or runaway, cycle is established.
During the night, open water radiates a large quantity of heat, about 90 Watts per square metre. A snow-covered sea-ice slab floating on the ocean surface 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 area.
Ocean currents have a special influence on the climate. They act as heat pumps, as they distribute the energy stored in the oceans around the entire globe. The most well-known example of this is the Gulf Stream, which transports warm water from the tropics diagonally over the Atlantic to Northern Europe and provides Britain with a mild climate and ice-free ports. 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 on the climate.
CryoSat – the first "Living Planet" mission
Much of the uncertainty in the climate models of today is due to the lack of precise measurement of the polar ice and its development. Experts estimate 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 be 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 at an altitude of 720 km. From there, its radar will measure the thickness and circumference of the polar ice sheets and sea-ice cover. Earlier radar satellites, such as the European ERS 1 and 2 or Envisat, are only equipped with a single antenna. With this, they can gather information about uniform ice surfaces over a large area. CryoSat, on the other hand, has two antennas. Similar to the way in which humans, with two eyes, can see in 3-D, CryoSat's double radar will be able to scan the 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 with very steep walls in the polar seas, glaciers or ice sheets.
To achieve this extraordinary precision, the orbit 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 on-board instrument called DORIS. The altitude information , which is thereby produced, is then conveyed via the normal data stream to the ground station.
CryoSat's outer surface also incorporates a laser retro-reflector. Similar to cats´ eyes on warning posts on the edge of a road, it reflects a ray of light. A laser beam transmitted from a ground station and reflected by CryoSat would enable the height of the satellite to be determined from the transit time.
CryoSat's radar altimeter works day or night 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 will provide information about the rate of change of these ice sheets.
Working within a tight budget
EADS Astrium, as the prime contractor for CryoSat, is responsible for a consortium of 31 companies. EADS Astrium itself is building the satellite platform and will integrate all the instruments. Ultimately, Astrium is responsible to ESA for the reliability of the whole satellite.
From the beginning, the special challenges of the CryoSat project for EADS Astrium's engineers were the apparently contradictory requirements of high reliability, tight timescales and low cost. In the meantime, the elegant simplicity of the satellite architecture and the proven hardware components supplied by the sub-contractors have demonstrated that the programme can be implemented on schedule. The close partnership between scientists, ESA and the industrial consortium permits a lean management team and, at the same time, more transparency and faster reaction time during the development and construction phases.
EADS Astrium is Europe's leading satellite system specialist. Its activities cover complete civil and military telecommunications and Earth observation systems, science and navigation programmes, and all spacecraft avionics and equipment. EADS Astrium is a wholly owned subsidiary of EADS SPACE, which is dedicated to providing civil and defence space systems. In 2003, EADS SPACE had a turnover of more than 2.4 billion euros and about 12,000 employees in France, Germany, the United Kingdom and Spain.
EADS is a global leader in aerospace, defence and related services. In 2003, EADS generated revenues of 30.1 billion euros and employed a workforce of more than 100,000.
Friedrichshafen, May 2004/04007
EADS SPACE (FR)
Tel.: +33 (0) 1 34 88 35 78
EADS SPACE (UK)
Tel.: +44 (0) 1438 77 3698
EADS SPACE (GER)
Tel.: +49 (0) 7545 8 91 23
|Mass:||approx. 650 kg|
|Instruments:|| Radar altimeter (SIRAL)
Data receiver (DORIS) Laser retro-reflector
|Height resolution:||1 to 3 cm|
|Horizontal resolution:||approx. 300 m|
|Total finance value:||approx. 140 million euros|
|of which industrial contract:||approx. 70 million euros|
|Mission duration:||over 3 years|
|Orbit:|| 720 km altitude,
92 degrees inclination
|Planned launch date:||autumn 2004|
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