In what can be considered a proof of concept for using extremely high frequencies to ease clutter on congested terrestrial radio waves, a Finnish satellite has successfully sent the world’s first 75 GHz signals from space.
The W-Cube nanosatellite was launched into space on 30 June 2021 from Cape Canaveral, Florida on a SpaceX Falcon 9 space launch vehicle as one of the satellites on the Transporter 2 mission with 88 satellites. W-Cube was placed into its own orbit on 22 July 2021 and the first contact between the satellite and the Finnish Reaktor Space Lab (RSL) ground station was established by the next day.
The satellite, ordered from Finland by the European Space Agency (ESA), is broadcasting the signal using a radio beacon system developed by VTT Technical Research Centre of Finland and Germany’s Fraunhofer IAF. The satellite is now modelling, for the first time ever, how a 75 GHz signal can penetrate the Earth’s atmosphere. This opens possibilities for the utilisation of the high millimetre-wave frequency range in communications satellites in the future.
A new frequency range and additional capacity will be needed in the next few years as the number of data communication satellites increases and big flocks of satellites such as Starlink (operated by SpaceX) are deployed. “Today’s lower frequency ranges are divided into narrow bands over which satellites and terrestrial radio links compete. Meanwhile, no bands in the high frequency range have been shared yet among the various applications. A free, wide bandwidth enables rapid transfer of information and connections in, for example, 5G and 6G networks and in remote areas such as Northern Finland. The European Space Agency has a mission to offer these connections and in this way to invest in European competitiveness,” commented VTT senior scientist, Jussi Säily.
The penetration through the atmospheric layers by the signal needs to be understood before the frequency range can be utilised. W-Cube’s dual-frequency radio beacon system sends a 75 GHz signal through the Earth’s atmosphere to measuring ground stations in Graz, Austria and to Espoo, Finland. The data from the measurements helps in modelling how weather phenomena in space and in the atmosphere affect the signal propagation and polarisation. In addition, W-Cube broadcasts a 37,5 GHz signal, making it possible to compare the information on measurements with previous models at a low frequency range.
To save battery power, the beacon signals are only switched on when they can be detected by measuring stations in Europe. At other times the satellite charges its batteries with its solar panels. The satellite orbits the Earth approximately once every 1,5 hours and is visible from the ground station (from horizon to horizon) for about 10 minutes at a time.
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