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For large broadband satellite networks, the number of gateways may be such that the cost of the ground segment exceeds the cost of the satellite, even when using Q/V band in the gateway feeder link. The usage of the spectrum available in W-band (70/80 GHz) for Satcom systems feeder link in future High-Through-Put systems will significantly reduce the number of required gateways and consequently the overall cost of the ground segment. However, the atmospheric channel- propagation models available from the ITU are known to be accurate up to 30~40 GHz. Therefore, new measurement campaigns are needed to characterize the atmospheric channel propagation at W-band.
In this activity, a Cubesat-like nanosatellite is used to embark a beacon transmitting in W-band in order to perform channel propagation measurements. The LEO orbit of the nanosat, although different from the geostationary orbit of future operational satellites exploiting W-band, will allow the project to characterise the major satellite channel impairments. In addition, supporting software tools will be used to bridge the gap between the relatively short LEO measurements and the statistical reliability needed for GEO propagation measurements, in particular an atmospheric channel simulator. The collected channel measurements will be used to tune the atmospheric channel simulator and the satellite movement effects will be de-convolved from measurements in order to extrapolate the equivalent GEO propagation channel characteristics.
The activity includes the design and development of the W-band beacon together with the propagation receive terminal. A measurement campaign of at least two years of duration is in the final phase of the project.
The challenges in this project are the design of the space segment, which has to provide sufficient transmission power to be able to be received with a cost-effective ground station, which measures the signal trough the atmospheric path. Therefore, a wide dynamic range of the signal shall be covered by the ground station and its beacon receiver. A fast and precise tracking antenna is required to measure the beacon as accurately as possible.
The atmospheric channel-propagation-models available from the ITU are known to be accurate up to about 30 GHz to 40 GHz. Therefore, new measurement campaigns are needed to characterize the atmospheric channel propagation at W-band.
In this activity, a CubeSat-like nanosatellite will be used to embark a beacon transmitting in W-band in order to perform channel propagation measurements. The LEO orbit of the CubeSat, although different from the geostationary orbit of future operational satellites exploiting W-band, will allow the project to characterise the major satellite channel impairments.
The improvement targeted by this activity is the augmentation of the ITU-R models for W-band with specific measurements. An accurate characterization of the W-band channel over Europe is the goal.
The main system building-blocks of the architecture consist of the space segment and the ground segment. The space segment covers the beacon generation for the circular polarised beacon for Q and W-band. The amplifier on board provides, together with a mission optimised antenna, sufficient EIRP to allow a wide dynamic range of the measurement on ground. The satellite has a telemetry link which is controlled via the ground station in Helsinki. The measurement ground station is placed in Graz / Austria and has a fast-tracking antenna and the beacon receiver. From previous projects, it is possible to use the beacon reception in Q Band from Alphasat Aldo Paraboni payload as well. The analysis of the measured data is processed off-line and the collected channel measurements is used to tune the atmospheric channel simulator and the satellite movement effects is de-convolved from measurements in order to extrapolate the equivalent GEO propagation channel characteristics.
Phase 1 of the project defines the architecture of the system taking into account the requirements given by the Statement of Work, but also the lessons learnt from previous experiments in Q/V band and Ka band. A detailed PA/QA plan definition helps to ensure that the mission is operational for at least 2 years.
Phase 2 covers the development and qualification phase of the satellite and ground station development. It includes the following subsystem design and implementations: CubeSat satellite platform, W-band and Q-band beacon development including some specifically designed and optimised RF front-end components for the payload, launch procurement and in-orbit testing, ground station development including the design and implementation of optimised low-noise amplifier for the radio receiver, installation and commissioning.
Finally, phase 3 covers the measurement campaign and operational tasks for the spacecraft and ground station. The telemetry is controlled from the ground station in Helsinki and the measurement ground station is placed in Graz/Austria, where there is already an existing Q/V-band ground station operating on the Alphasat beacons. All collected data are processed by JOANNEUM RESEARCH and will help to improve the knowledge in using the W-band for future satellite communication links