Daily monitoring of weather and climate change, crop failure control, desertification and deforestation observation: these are just a few examples of the uses for the unique image data delivered by Proba-V from an altitude of 820 kilometers and accessed by approximately 10,000 registered users worldwide. ‘V’ stands for vegetation and refers to the environmentally focused mission of the miniature satellite, which was launched into orbit in 2013 by the European Space Agency (ESA). Cartography, however, is not its only job.
Promising technologies on test space voyages are also aboard the refrigerator-sized satellite. Among them, the satellite communication system with a gallium nitride (GaN) amplifier of German origin has raised high hopes for optimal image transmission to its Belgian ground station in the X frequency band (8 GHz). “With gallium nitride as a semiconductor material, we expect a 5- to 10-fold improvement in signal strength and data trans- mission,” said Andrew Barnes, Director of the ESA project. He and a consortium of European companies and research institutes were eager to pave the way for the GaN semiconductor into space.
There are several arguments in favor of using this technology instead of existing alternatives: unlike silicon- or gallium-arsenide-based semiconductors, GaN operates reliably and in a wide frequency range up to 100 GHz – even at high voltages and temperatures. The material also enables smaller and lighter circuit generation, is radiation-resistant, and requires no active cooling.
The MMIC amplifier (Monolithic Microwave Integrated Circuit) developed by the Fraunhofer Institute for Applied Solid State Physics (IAF) in Freiburg, Germany, is able to utilize these advantages in space for the first time. The chip, just a few square millimeters in size, required an innovative package concept that was fulfilled by partners SCHOTT Electronic Packaging and Tesat-Spacecom.
They sought to develop a high-tech housing that would protect the chip while also enabling its high-frequency waves to be transmitted with necessary strength. At the same time, the housing would have to conduct heat generated inside to the outside with the highest possible efficiency so as not to impair the chip’s performance.