The ice mission
The polar regions play a vital role in the Earth’s climate and ecosystems. Scientists assume that the polar ice masses will retreat considerably due to global warming; up to now, however, there is little selective data on these large, unpopulated and difficult-to-access regions. Data provided by the CryoSat-2 radar altimetry mission – on changes in the thickness of ice sheets and polar ocean sea-ice cover – should remedy this information deficit and provide a global overview for researchers.
CryoSat-2 prepares to leave Airbus Defence and Space’s Friedrichshafen site. © Airbus Defence and Space
CryoSat-2 is operating in an unusually high-inclination orbit of 92° in order to get the best visibility of higher latitudes (>72°) and sufficient cross-overs up to the polar regions. The orbit is not sun-synchronous, so the direction from which sunlight falls on the satellite is constantly changing. This presented some challenges to satellite design: all parts are at some time exposed to the full heating power of the sun, while at other times half the satellite is in permanent shadow for weeks on end. In addition, the operation of the primary SIRAL instrument demands that its antennas point towards Earth’s surface within a few tenths of a degree. This means that rotating the satellite to face the sun is out of question.
CryoSat-2 – a satellite on an icy mission. © ESA – AOES Medialab
And if these mission objectives were not already taxing enough, CryoSat-2 is one of the ‘Opportunity’ Earth Explorer missions, lower-cost satellites that are relatively quick to build and fly so that they can quickly address areas of immediate environmental concern – but of course without compromising quality. So how did our engineers contrive to marry budget constraints with impeccable science delivery? They dispensed with costly mechanisms – Cryosat-2 has no deployable solar panels, and in fact its only moving parts are a few valves in the propulsion system – and arranged the geometry of the satellite to achieve their purpose.
The solar panels are rigidly fixed to the satellite body, forming a 'roof' with a carefully optimised angle, which will provide adequate power under all orbital conditions and still fit within the launch vehicle. This is the reason for Cryosat-2’s characteristic if somewhat chunky shape.
|CryoSat-2’s rigid solar panels give the satellite its characteristic ‘roof’ shape. © ESA – P. Carril|
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