In July 2024, Sunrise completed its third successful science flight. The Sunrise iii observatory had been upgraded significantly after the two previous successful flights in 2009 and 2013, to tackle the most recent science challenges concerning the solar atmosphere. Three completely new instruments focus on the small-scale physical processes and their complex interaction from the deepest observable layers in the photosphere up to chromospheric heights. Previously poorly explored spectral regions and lines are exploited to paint a three-dimensional picture of the solar atmosphere with unprecedented completeness and level of detail. The full polarimetric information is captured by all three instruments to reveal the interaction between the magnetic fields and the hydrodynamic processes. Two slit-based spectropolarimeters, the Sunrise UV Spectropolarimeter and Imager (SUSI) and the Sunrise Chromospheric Infrared spectro-Polarimeter (SCIP), focus on the near-ultraviolet (309 – 417 nm) and the near-infrared (765 – 855 nm) regions respectively, and the imaging spectropolarimeter Tunable Magnetograph (TuMag) simultaneously obtains maps of the full field-of-view of $46\times 46$ 46 × 46 Mm² in the photosphere and the chromosphere in the visible (525 and 517 nm). The instruments are operated in an orchestrated mode, benefiting from a new Image Stabilization and Light Distribution unit (ISLiD), with the Correlating Wavefront Sensor (CWS) providing the autofocus control and an image stability with a root-mean-square value smaller than 0.005”. A new gondola was constructed to significantly improve the telescope pointing stability, required to achieve uninterrupted observations over many hours. Sunrise iii was launched successfully on 10 July 2024, from the Esrange Space Center of the Swedish Space Corporation near Kiruna (Sweden). It reached the landing site between the Mackenzie River and the Great Bear Lake in Canada after a flight duration of 6.5 days. In this paper, we give an overview of the Sunrise iii observatory and its instruments.

GaN high-electron-mobility transistors (HEMTs) are promising next-generation devices in the power electronics field which can coexist with silicon semiconductors, mainly in some radiation-intensive environments, such as power space converters, where high frequencies and voltages are also needed. Its wide band gap (WBG), large breakdown electric field, and thermal stability improve actual silicon performances. However, at the moment, GaN HEMT technology suffers from some reliability issues, one of the more relevant of which is the dynamic on-state resistance (R_{ON_dyn}) regarding power switching converter applications. In this study, we focused on the drain-to-source on-resistance (R_DSON) characteristics under ⁶⁰Co gamma radiation of two different commercial power GaN HEMT structures. Different bias conditions were applied to both structures during irradiation and some static measurements, such as threshold voltage and leakage currents, were performed. Additionally, dynamic resistance was measured to obtain practical information about device trapping under radiation during switching mode, and how trapping in the device is affected by gamma radiation. The experimental results showed a high dependence on the HEMT structure and the bias condition applied during irradiation. Specifically, a free current collapse structure showed great stability until 3.7 Mrad(Si), unlike the other structure tested, which showed high degradation of the parameters measured. The changes were demonstrated to be due to trapping effects generated or enhanced by gamma radiation. These new results obtained about R_{ON_dyn} will help elucidate trap behaviors in switching transistors.

Dynamic R_ON is a key parameter in terms of device reliability and the efficiency of power-switching converters. In this study, commercial off-the-shelf GaN-on-Si power high-electron-mobility transistors (HEMTs) were irradiated using different regimes of accumulative gamma rays with a ⁶⁰Co source of photon energy (1.33 MeV), while a base temperature of 53 °C and 133 °C during the irradiation test was applied. This test campaign had the objective of investigating how the combination of gamma irradiation and temperature affects dynamic on-resistance (R_ON) behaviour. The results indicated that gate voltage bias stress affected the degradation of dynamic on-resistance when irradiation was applied, and that temperature was an accelerating factor in dynamic on-resistance degradation. Finally, we obtained a partial reduction in dynamic R_ON when a total ionising dose of around 140 krad(SiO₂) was applied and the base temperature during the irradiation test was not high.

The European Power Standard, used when designing and implementing spacecraft power buses, imposes stringent impedance requirements for high reliability and robustness, unlike other standards such as those from the American Institute for Aeronautics and Astronautics, SAE International, or the International Deep Space Interoperability Standard. These strict requirements, however, may limit innovations leveraging new technologies resulting from recent component advancements. This work examines the implications of the European Power Standard’s output impedance criteria for stability and its impact on payload power supplies, focusing on the potential to increase operational frequencies in power supply topologies to reduce system volume and mass, which are key factors in space technology.

The main contribution of this work is the demonstration of the positive influence of RC snubber circuits in a multiple-output buck-type converter beyond its original purpose. They not only improve the switching behaviour but also the frequency response and dynamic cross-regulation. Being only the low-power RC snubbers responsible for the overall converter stability and dynamic cross-regulation improvement, the use of smaller RC devices and low-power switching diodes is an additional benefit of this technique. The effect of using RC snubbers in the low-power outputs is similar to output inductor coupling.

Electronics is a challenging part of a space mission that has to fulfill stringent requirements linked mainly to the satellite launch and mission environment. Power conversion and distribution systems are among the most critical elements in space electronics, as they are vital in any satellite. A large scientific space mission development lasts several years. Throughout its payload development process, each instrument usually endures numerous changes and updates of its requirements, being the power conversion and distribution system one of the most affected due to the evolution of the loads. This work presents the advantages of a custom design compared to an off-theshelf design of the Power Converter Module of the Polarimetric and Helioseismic Imager (PHI) on board the Solar Orbiter, an ESA/NASA satellite launched in February 2020, thereby highlighting that this approach was key to meeting the most demanding requirements of this mission. Telemetry data since the beginning of the mission will be presented to confirm the chosen design approach to be correct.