CryoSat - A Satellite on an Icy Mission

CryoSat, the ice research satellite is completed: The satellite developed and built by EADS Astrium for the European Space Agency ESA, is currently being prepared for its transportation to Russia. It is to be launched from the Plesetsk Cosmodrome (approximately 800 km north of Moscow) in mid-September on board a Rockot launcher provided by 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 1950, 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.

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:

Polar ice reflects a large proportion of the sunlight and 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. This might result in a self-accelerating warming up.

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, providing Britain with a mild climate and ensuring ice-free ports up to northern 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 on the climate.

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.

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 huge ice sheets.

EADS Astrium, as the prime contractor for CryoSat, is responsible for a consortium of 31 companies. EADS Astrium (Friedrichshafen) 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.

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.

EADS SPACE is also considerably involved in other satellites of the Earth Explorer Missions which are being built. EADS Astrium (UK), for example, is the prime contractor for the ADM-Aeolus wind mission, whereas the Aladin instrument is being developed by Astrium (F). In addition to the lead in the CryoSat ice satellite, EADS Astrium (Friedrichshafen) is also responsible for the platform and the satellite integration of GOCE, the surfer of the gravitational field. Astrium Spain develops and builds the Miras payload of the SMOS mission for the acquisition of data on soil moisture and ocean salinity.  

The launch provider Eurockot (Bremen), a unit of EADS SPACE, will carry out the launches of the satellites CryoSat, Goce and Smos on board its Rockot launchers from Plesetsk (800 km north of Moscow).

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, wholly owned subsidiary of EADS SPACE, which is dedicated to providing civil and defense space systems. In 2004 EADS SPACE had a turnover of €2.6 billion and 11,000 employees in France, Germany, the United Kingdom and Spain.

EADS is a global leader in aerospace, defense and related services.

In 2004, EADS generated revenues of € 31.8 billion and employed a workforce of more than 110,000.

Mass: 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: at least 3 years

Orbit: 720 km altitude, 92 degrees inclination

Planned launch date: September 2005

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