VTT's Cutting-Edge W-Cube Satellite Ends Its Four-Year Successful Journey In Earth Orbit

The W-Cube nanosatellite, ordered from Finland by the European Space Agency, is currently sinking towards the atmosphere at the end of its successful mission. The satellite will also return with a radio beacon system, which is mainly the work of VTT. It achieved the goal of demonstrating for the first time that the extremely high and ultra-fast 75 gigahertz frequency range can be used in future communications satellites.

The European Space Agency 's W-Cube satellite is currently rapidly descending from a height of just over 200 kilometers above the Earth's surface. Scientists expect that communication will be lost soon as atmospheric friction increases, causing the satellite to burn up and be completely destroyed in the atmosphere. This is expected to happen within a few days.

"This concludes a very successful space mission that has been fascinating to be a part of. The W-Cube satellite showed that the much higher frequency ranges currently in use can be utilized in satellite communications and achieve very high performance. This opens up the possibility of bringing faster communications connections to consumers in Europe, even directly to smartphones," says Jussi Säily , Principal Scientist at VTT and Project Manager of the project .

He reminds us that societies depend on the functioning of telecommunications connections. Satellite-based connections are more difficult to disrupt than terrestrial connections. EU decision-makers have also become aware that the United States can limit the satellite connections it controls if it wishes, which motivates the development of real European alternatives.

Clearly higher radio frequencies than today bring valuable advantages: many ultra-fast and still free frequency bands will be available. The rapid development of semiconductor technology enables commercial applications of millimeter-wave technology with good efficiency. Efficiency is important in satellites because it reduces power consumption.

The size of a one and a half liter milk can
W-Cube was the first satellite ordered from Finland by the European Space Agency (ESA) . The satellite, only slightly larger than a one and a half liter milk can, was launched into orbit around the Earth on June 30, 2021. It transmitted essential radio signals for its mission using a radio beacon system developed by VTT and the German Fraunhofer IAF.

The Finnish company Kuva Space also played an important role in the reliable functioning of the satellite platform. It consists of, among other things, the chassis, attitude control system and solar panels. The company was also responsible for operations from its own ground station.

"Through the experience of W-Cube, we are developing our own operations so that the operation of satellites is fully automatic. We have now launched five nanosatellites and achieved a 100% success rate, which many others have not been able to achieve," says Janne Kuhno , Chief Engineer and Founding Partner of Kuva Space.

For Finland, the value of the W-Cube basic project was approximately one million euros, of which VTT's share was approximately half. VTT built and tested the payload and mechanics, such as the control electronics, frequency synthesizer and antennas.

The purpose of the W-Cube satellite was to determine how much the Earth's atmosphere and its phenomena, especially raindrops and rain clouds, attenuate very high-frequency radio signals. There was no previous experience with this. The signal was successfully received at ground stations in Finland, Austria and the Netherlands.

"At our own satellite ground station in Otaniemi, we have been able to receive signals until the very last few days. Based on long-term measurements made under different climatic conditions, we have been able to create attenuation models that are absolutely essential when designing and dimensioning future high-speed communications satellites," says Säily.

The four-year operational life of the W-Cube is a good achievement for its size. Nanosatellites have a maximum lifespan of five to six years.

VTT has already qualified for the next project with ESA
VTT has, together with the Austrian Joanneum Research, produced several publications on the modelling. ESA has been very pleased with the results.

“W-Cube has brought a good reputation to VTT, and I am already leading the next, larger project, which aims to launch the significantly larger 6G-Lino satellite , also ordered by ESA, next year,” says Jussi Säily. W-Cube was his first satellite project, but he has long led 6G research and other mobile network projects at VTT.

The use of high, so-called millimeter-wave frequencies in satellites also requires more precise and long-term modeling measurements. This requires a geostationary satellite that remains stationary at a distance of 36,000 kilometers from Earth. W-Cube only transmitted a so-called unmodulated carrier wave at two different frequencies (37.5 and 75 GHz)

Before the now tested frequency ranges can be utilized in commercial communications satellites, they must also be tested with real, modulated communications signals that contain information, such as voice and video.

VTT's ground station will also be used for drone testing
VTT's satellite earth station, which will be put into operation in 2024, is located on the roof of the Micronova building in Otaniemi, Espoo. It will probably be used in other projects. Reception of the radio beacon signal from ESA's geostationary Alphasat satellite is already underway. Alphasat was launched in 2013. The lower frequency range of its beacon signal, the so-called Q-band, requires modifications to the receiver at the earth station.

The ground station, which can turn quickly and follow a target, can also be used for other purposes. The speed is illustrated by the fact that the nanosatellite can be visible to the ground station for a maximum of ten minutes as it flies from horizon to horizon. Another possible target for further use are drones, in which the use of millimeter frequencies can be tested for data transmission.

W-Cube satellite

• Three Cubesat units, or 3U, in size. One Cubesat unit is approximately 10 x 10 x 10 cm.
• Design, construction and testing phase 2018–2021. Launch 30 June 2021.
• Operational phase until mid-September 2025.
• A radio beacon based on VTT's cutting-edge technology.
• Showed that the new frequency ranges in the so-called E-band (71–86 GHz) and W-band (75–110 GHz) can be utilized in satellite communications.

For more information, visit https://www.satcat.com/sats/48965.