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More bandwidth for Earth observation

DLR makes progress with a new radar mission at the World Radiocommunication Conference

Mobile telephones, high-speed Internet, up-to-date meteorological data and navigation programs available anytime, anywhere – all thanks to satellites. Bandwidth and frequencies that are revised every three to four years at the World Radiocommunication Conference play an important role in this. This year’s conference – attended by 3800 delegates from 193 countries – is being held in Geneva and is the largest World Radiocommunication Conference thus far. Ralf Ewald, from the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) Space Administration, is the Frequency Coordinator and, until 27 November 2015, together with German delegates, will revise the bandwidth and frequency allocations that will be available to, among other things, future satellite missions. Now, an agreement has been reached for a new X-band German radar satellite mission.

Interview by Martin Fleischmann

What is being negotiated at the World Radiocommunication Conference?

Ewald: Here in Geneva, we are negotiating international law. Although use of the radiofrequency spectrum in Germany is subject to national law and is regulated by the German Federal Network Agency (Bundesnetzagentur; BNetzA), radio signals and the use of frequencies are not subject to national borders. We speak of cross-border frequency use as soon as somebody operates a mobile telephone to place a call while abroad. Naturally, this also applies to satellites that constantly pass over other countries. The International Telecommunication Union (ITU) is responsible when radio signals cross national borders. It deals with all ‘transnational’ issues. These regulations are defined in an international treaty, and then in most cases implemented into national law. The World Radiocommunication Conference is usually held every three to four years to revise this international contract whenever it becomes necessary. Each country sends a delegation to this conference to represent their various national interests. This time there are 70 German delegates in Geneva – the largest group from Germany ever to attend.

That shows the significance of this radio communication summit. Why are these negotiations so important?

Ewald: We have a problem; ongoing technical developments mean that every service – whether it is mobile telephony, science or satellite communications – needs more bandwidth. That is a fact of life. Unfortunately, the frequency spectrum that can be used in this way is limited. This is why our delegation, led by the German Federal Ministry of Transport and Digital Infrastructure (Bundesministerium für Verkehr und digitale Infrastruktur; BMVI), and supported by the Bundesnetzagentur, representatives of the industrial sector – for instance, mobile communications providers – and DLR, are negotiating to obtain more bandwidth and ensure its meaningful use. DLR is representing the interests of the German government with regard to satellite radio services used for scientific purposes. My task is to carry forward these issues from a German perspective, to ensure that the contractual text ultimately reflects our interests.

There is also an extremely important topic under negotiation for DLR…

Ewald: Yes, precisely. Politically speaking, item 1.12 on the agenda could have given rise to conflict. Put in simple terms, it is a question of more bandwidth. DLR and Airbus Defence and Space are preparing the next generation of Synthetic Aperture Radar (SAR) satellites to conduct Earth observation in X-band – the spectrum in which the twin radar satellites TerraSAR-X and TanDEM-X operate. We want to produce images that, in terms of resolution, are comparable with optical images – so essentially, with a resolution better than 25 centimetres per pixel. The highest resolution that TerraSAR-X can offer is approximately one metre. Given that resolution is synonymous with bandwidth, we need a larger frequency allocation to achieve this improvement. So, we have to receive more bandwidth to acquire the resolution we are targeting. Until now, we had agreed on 600 megahertz, which is only approximately half of the necessary bandwidth. Now we have been granted 1.2 gigahertz, twice this amount.

Why was it so difficult to find a solution?

Ewald: We applied for an additional 600 megahertz, so many of the applications currently in use would come under pressure if our attempt to receive a total frequency allocation of 1.2 gigahertz were to be approved. Initially, this prompted several countries to reject our proposal. We wanted to know exactly how big the problem was and whether their concerns were justified. To analyse the issue, we have been conducting studies for the last three years. Now we have attempted to reach a common standpoint. Other countries attempting to secure more bandwidth in this frequency band – and who share our strong interest in radar-supported Earth observation – have helped us. These countries – for instance the oceanic nations – need better Earth observation technology to provide their emergency services with more up-to-date and high-resolution map data when faced with catastrophic flooding. We spent days in innumerable multilateral and bilateral meetings to arrive at a solution. Now we have found a good compromise, which all 193 member states – all resolutions at the World Radiocommunication Conference have to be passed unanimously – have agreed to. The outcome is an additional 600 megahertz of bandwidth and the option for an X-band Earth observation mission in hitherto unseen, almost optical resolution.