Europe’s ice mission

• Under construction
• Due for launch in 2009

Ice plays a major role in the Earth’s climate system. The loss of polar ice could affect sea level, ocean currents and how much heat is absorbed from the Sun. To understand the impact of global warming it is vital to work out how much ice there is on our planet and monitor any changes. CryoSat-2 will measure precise changes in the thickness of the polar ice sheets and floating sea ice.

The first CryoSat mission was launched in 2005 but failed to reach orbit. An investigation found there had been a failure in one of the upper stages of the rocket after take-off. Because the mission is so important, a replacement satellite was given the go-ahead. CryoSat-2 is currently under construction.

CryoSat-2 has the same objectives as the original spacecraft. It will make measurements of the ice sheets of Antarctica and Greenland. It will also monitor variations in Arctic sea ice. Data from the mission will be compared with information gathered from other ESA satellites (such as Envisat) and the NASA satellite IceSat, to build up a picture of long-term trends in the Earth’s ice cover.

CryoSat-2 will be able to measure ice thickness to the nearest centimetre. To achieve this remarkable accuracy, an extensive ‘validation programme’ is being carried out. This involves polar expeditions to take measurements of ice and snow thickness. The campaign also uses aircraft to make radar measurements. This data will be used to calibrate the instruments and check the performance of CryoSat-2.

Mission facts

• Without ice our climate would be radically different.
  
  
• The white surface of ice reflects sunlight back into space. If the ice melts, more heat will be absorbed by the dark surface of the ocean. This will cause the waters to warm and more ice to melt. This is known as a feedback mechanism: the less ice, the more heat is absorbed which leads to even less ice!
  
  
• Arctic sea ice also keeps us warm. The annual cycle of freezing and thawing helps keep ocean currents flowing. These currents are part of the ‘giant heat pump’ that moves heat around the globe.
  
  
• In winter, as the sea ice forms, salt is released. This increases the density of the water which causes the surface waters to sink. This downward convection pushes water from the Arctic towards the equator. This cold water is replaced by warmer water from the equator flowing north towards the pole.
  
  
• Without this warm water, the climate of the UK would be radically different. The most alarming studies suggest that without sea ice, Europe would be thrust into a new ice age.
  
  
• There is also evidence to suggest that climate change is causing glaciers to melt. This will eventually lead to rises in sea level and the loss of land. For the UK this will put many coastal areas at increased risk of flooding. For low-lying countries, such as Bangladesh, this could prove even more disastrous in the future.
  
  
• The break-up of Arctic sea ice would also have an impact on wildlife. A recent study led scientists to suggest that if the trend continues, polar bears could lose their habitats and become extinct within 50 years.

Technology

CryoSat-2 is equipped with highly accurate radar which has been specially designed for measuring the thickness of ice. It uses a twin radar system with two onboard radar receivers. This allows a 3-D view of the ice to be built-up.

The spacecraft will send short radar pulses to the Earth and calculate the time it takes between the signal leaving and returning to the spacecraft. By knowing the exact position of the satellite, the height and thickness of the ice can be determined to the nearest centimetre.

CryoSat-2 also has an unusual appearance: it looks a bit like a house and has virtually no moving parts. This is because, unlike most missions, it has been specially designed to fly in an orbit that takes it right across the poles. As it orbits, its position relative to the Sun will change. In a traditional satellite design this would have meant the spacecraft having to keep adjusting its solar panels so they were always pointing at the Sun, otherwise it would run out of power. To overcome this problem, CryoSat-2’s panels are set at an angle to make sure they are always getting enough sunlight.

UK involvement

The science team for CryoSat-2 is being led from the UK.

The CryoSat-2 mission was first proposed by Professor Duncan Wingham of University College London. Head of the Centre for Polar Observation and Modelling at the Natural Environmental Research Council (NERC), he led the team that wrote the original CryoSat proposal in 1998. Today, Professor Wingham serves as CryoSat-2 Lead Investigator.

Industrial partners include Marotta UK Limited which supplies high-performance fluid control components for space applications.

AEA provided Cryosat-2's battery and SciSys developed the satellite's onboard software.