RF Satellite Communication
With almost a century of heritage in radar and RF technology innovations for the Dutch MoD and for space applications, TNO pushes fundamental research in RF technology for satellite communication.
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TNO is working on this new optical communication technology that uses satellites to send information to Earth. This happens via invisible light signals and enables much faster data transfers than using the radio frequencies currently employed for communication everywhere.
Laser satellite communication ensures that you can send more data. It uses much less power and at the same time, the efficiency is higher. Moreover, it can be at least 10 times faster than normal communication. You can use laser satellite communication to process a terabit of information per second - that's about 125 gigabyte. Or, more tangible: streaming 200,000 Netflix HD quality movies in parallel.
The laser signals are used to directly connect satellites with so called inter-satellite links but also to connect satellites and terrestrial stations on Earth. It’s also possible to install such an optical terminal in an aircraft so that you can use the internet in the air. Laser satellite communication works best if you build a network of several satellites that exchange data and then send it back to Earth.
That’s a handy thing to have here on Earth. It gives you reach anywhere in the world. But beyond the convenience, laser satellite communication is actually a necessity. For example, the advance of the self-driving car is relentless, and such autonomous vehicles process gigabytes of data every second. And not only are cars becoming smarter (and therefore need more data), our homes can also do more and more. Thermostats, refrigerators and smoke detectors; they are all internet connected and thus increasingly consume data.
The current radio frequency spectrum is no longer sufficient to process all that data. It is too limited in terms of data processing, and many people already use it. The result is scarcity and malfunctions.
You have to use dozens or even hundreds of satellites to make a good laser communication network. Together they can then reach the entire surface of the Earth. There are a number of companies and institutions that are building such a network. SpaceX does it with StarLink, the European space agency ESA is building EDRS. Such networks consist of satellites that are becoming smaller and cheaper all the time.
At the moment, more than 30 researchers at TNO are working on the development of this form of communication. TNO is not building the entire satellite, but the optical part with which the satellites communicate with terrestrial stations and the optical terminals for inter-satellite communications. TNO is also developing the key technologies needed for the future, more advanced, terminals. High precision mechanisms, optical components, mirrors manufacturing and photonics components, are just some examples.
One key obstacle, for example, is the price. In a network of satellites each satellite contains four terminals, so a network of dozens of satellites will quickly require hundreds of terminals, and that drives up the costs. An important task for TNO is to be able to produce these terminals in bulk, but above all to make them smaller, cheaper and therefore commercially more appealing.
One of those technologies that TNO is working on is the 'TOmCAT', the 'Terabit Optical Communication Adaptive Terminal'. Adaptive optics is a vital sub-system for these ground terminals since laser communication is affected by turbulence in the atmosphere and so the connection is not optimal. Adaptive optics stabilise that connection.
At the moment, we are working hard on laser satellite communication, but there is still a long way to go. Last year (2019) we have tested the adaptive optics performance, the stability and precision of the laser beam between two stations that were ten kilometres apart. It appeared that using our adaptive optics system substantially improves the performance i.e. 6 dB of improvement over 10km. As this demonstration was representative for a ground to GEO link (altitude of 39.000km above the earth) we also expect that performance improvement in the final product.
TNO is collaborating with Dutch and European Space and High-Tech industry on this development. There are many companies in our country that are already working on building microchips or other components relevant for laser satellite communication. TNO helps these companies to use their work processes and machines so that laser satellite communication components can be built easily. Both parties benefit from this.
It is not enough to make the technology cheaper. Commercial applications must also become available to make laser satellite communication affordable. Such communication is also very interesting for Defence purposes. For example, laser satellite communication is much safer than radio communication because it is much more difficult to wiretap.