Small Radar Satellites from a Small Country

 Small Radar Satellites from a Small Country

“The Netherlands is a leader in small satellites, that’s why we have to invest.” The Dutch space sector is making significant contributions to more accurate and more affordable Earth Observation, with developments in miniaturisation of instruments and satellites, in combination with smart formation flying.

Dutch SAR Knowledge Network

With the Knowledge Networks Scheme, the Netherlands is investing in technological breakthroughs and scientific cooperation in space travel. As part of this scheme, the ‘Dutch Knowledge Network on Radar Instruments and Applications’ (NL-RIA) is working on smaller radar instruments that can fly through space like a swarm.

A single and averaged ERS-2.SAR.PRI image of Amsterdam, The Netherlands (image size 12.5km by 12.5km). The canals within Amsterdam are clearly visible in the averaged image (source)

Radar instruments in space are on the rise. They are used for weather forecasts and climate research, but also, for example, for monitoring infrastructure, subsidence, detecting illegal construction work and in shipping. The advantage of radar instruments is that they can always observe, even when it is dark or raining. There is also a disadvantage: the instruments are large and complex. According to coordinator Paco Lopez Dekker, there is a great opportunity for the Radar Technology Knowledge Network and for the Netherlands.

Delft University of Technology

Dekker is associate professor of remote sensing at Delft University of Technology. He wants to make radar technology so small that it can fly on the smallest satellites, cubesats . But that is only possible if various parties in the Netherlands join forces: ‘An instrument is not separate from the satellite it flies on. And the satellite flies only by the grace of the users. The knowledge network unites the entire chain: from user and instrument builder to the people who install the instruments on the satellites. That’s where the added value lies.’

Example of a constellation of miniaturized radar altimeters. | Source: NL-RIA / dr. Yuanhao Li

The Radar Technology Knowledge Network has grown into a large group of knowledge institutions and companies that approach the subject from various disciplines. In addition to TU Delft, these include TNO, NLR, Airbus Defense and Space Netherlands and ISIS. Companies that work on applications of radar data from space, such as Swartvast, Metasensing, Deltares, FutureWater and VanderSat are also taking part. The focus is on the development of miniaturized radar altimeters and smart foldable radar antennas.

‘Ordinary cameras can easily be miniaturized’, explains Lopez Dekker. ‘That is much more difficult with radar instruments. We have developed a concept for a radar altimeter that fits on cubesats. ESA is interested in this technology, which is why we are currently building a working prototype with SME RFx solutions.’ If successful, it will be easier to do more altitude measurements with many different, small satellites. This leads to a new need and the second major research line of our knowledge network: distributed systems.

Satellite swarms

Future radar measurements will likely be made with a cloud of small satellites – a swarm – communicating with each other. The swarm can control itself, split up, and even ‘repair’ itself, should the need arise. And the swarm can make advanced observations that are not possible with a single satellite, such as direct motion detection. “We are one of the groups in the world that is working on the technology to make this possible. If we can make constellations fly the way we want, that will be a real game changer for radar measurements.’

Impression of a cloud of small satellites communicating with each other. Source: NL-RIA

Another important theme for the knowledge network is the further development of antennas. ‘The antenna is the most visible and most problematic component’, says Lopez Dekker. ‘If you want to generate a good signal, it has to be very large. We just want to make smaller instruments. That is why one of the researchers in the network is working on folding antennas. These are interesting for radar instruments, but also for communication systems. In fact, for all systems that use radio and microwaves.’

The added value of his knowledge network has been demonstrated in recent years, says Lopez Dekker. That is precisely why, as far as he is concerned, there should be no end to the collaboration. He dreams of a future in which the concepts that are now being developed actually fly into space as a national project. ‘We have focused on small satellites because the Netherlands is leading the way in this area. We have SMEs capable of building anything we propose. And the costs of such a project, unlike the development of a large satellite, are easily bearable for the Netherlands.’

However, a lot still needs to be done before Dutch radar instruments detect subsidence, support shipping or help in agriculture and forestry. ‘We run into the same problem as the other groups working on this: a lot of money is needed to arrive at a tangible, working prototype. We must also keep the collaboration alive after the Knowledge Networks Scheme and start finding funding. That is the challenge we face as a network.’

Read more

Check out the website of the the Dutch network on small spaceborne radar instruments and applications (NL-RIA)

Featured image (top): Maritime traffic in the English Channel in a composite image (2015-2019) of Sentinel-1 SAR data, composed by Simon Gascoin (source).

This post was translated from Dutch. The original post can be read on the Netherlands Space Office (NSO) website here (in Dutch).

Remco Timmermans

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