Pioneering Evaluation of GaN Transistors in Geostationary Satellites

In this paper, we present the results of a 6-year experiment in space that studied the effects of radiation in GaN electronics in geostationary orbit. Four GaN transistors in a Colpitts oscillator configuration were flown in the Component Technology Test-Bed aboard the Alphasat telecommunication satellite. A heuristic analysis was performed by observing the variation in the power output of the oscillators with the total ionizing dose gathered during the mission. The total ionizing dose was measured with a RADFET placed close to the GaN devices. The experiment showed that GaN is a robust technology that can be used in the space radiation environment of a geostationary orbit. The work presented here starts with a brief introduction of the subject, the motivation and the main goal. This is followed by the description of the experimental setup, including the details of the oscillator design and simulations, as well as the implementation of the test bead and the Components Technology Test Bed. Finally, the results obtained during the 6 years of experience in space are discussed.

APPLICATION OF PHOTOMETRY TO UNDERSTAND THE BEHAVIOUR OF GEOSTATIONARY OBJECTS ON ORBIT

One of the challenges of satellite characterization is the ability to not only determine the spacecraft or-bit, but also satellite operating status, orientation, size, bus type, and material properties. Positional observations allow us to determine and/or update orbital elements of satellites, but they do not afford an insight into the behaviour of a satellite in orbit. The article discusses the results of solving the inverse problem of astrophysics. How you can use photometric, astrometric information about a satellite, its lighting conditions, supplemented by additional information, to understand the behavior of a satellite in orbit. The results are shown using examples of four satellites in geostationary orbit. An algorithm for calculating the photometric and dynamic characteristics of geostationary objects is provided.