EADS Global Website - Next-generation surveillance

Current satellite observation systems circle the globe at low Earth orbit altitudes of between 600 and 900 kilometres, which means that at any given moment, they can only see the relatively small area they are flying over. Due to orbital mechanics, it takes several days before such satellites come back over the same zone for a revisit, requiring several months to provide coverage of entire continents.

This is why Astrium engineers are looking at designing a satellite capable of observing the Earth from 36,000 kilometres – the altitude at which satellites appear stationary over the planet, with visibility covering a very wide area. With GO-3S, it would be possible to observe the same zone continuously to gather imagery with a ground resolution of a few metres.

Such a system could bring numerous benefits for users, enabling virtually continuous viewing of the same spot at a very fast image 'refresh rate.' This could pave the way for security and surveillance services such as observing ships in port or vehicles near a border. The potential for delivering image rates of one per second – offering 'video-type' coverage – would open the way to even more sophisticated continuous surveillance applications.

Breaking barriers

Another key advantage of GO-3S’ large-scale coverage is the ability to monitor rapidly changing phenomena that affect several thousands of square kilometres – tracking seasonal plant growth or the hydrological situation of an entire water catchment area, for example. This is difficult for satellites that operate in low Earth orbit because the time needed to capture the area of interest could be greater than the duration of the phenomenon to be analysed.

The GO-3S project’s main challenge will be mastering the technologies required to make observations from the considerable altitude of geostationary orbit while obtaining the required resolution of three to five metres. To start, the satellite would require a very large diameter telescope, bringing into play such issues as the fine degree of polishing required for its mirror, along with the requirement for a level of high thermo-mechanical stability and very accurate pointing accuracy.

Did you know…?

Thanks to Astrium’s mastery of silicon carbide technology, the optics developed for the Herschel telescope will be massively boosted to make them up to 100 times better in the GO-3S satellite.

Expanding expertise

EADS Astrium has already produced a 3.5-metre-diameter telescope for Europe’s Herschel deep space observatory, launched in 2009. The expertise gained with the tools needed to build such a mirror – along with the related silicon carbide technology – can now be applied to GO-3S. Operating with visible light, the optical quality of the GO-3S spacecraft’s mirror will need to be at least 100 times greater than that for Herschel, which was designed to observe the universe in the far-infrared spectrum.

Additionally, an extremely precise control of the telescope’s temperature is required to prevent it from deforming while in space. The telescope for GO-3S will therefore need to be protected by a 'thermal cocoon' with a carefully adjustable temperature range. Finally, the problem of inherent microscopic vibrations generated aboard the satellite – which would disrupt pointing stability during imaging – can be addressed with an Astrium-patented system to correct line-of-sight jitter based on image analysis.

Astrium's feasibility studies will identify and prepare for the technological advances, and explore and analyse the vast range of innovative applications that such a system will offer its potential customers. Based on these findings, the project could take shape this decade, for a potential launch in 2020.