Airbus Defence and Space Netherlands

To support the development of free-space-optical (FSO) communication technologies, an end-to-end physical layer model of a satellite communication service was developed. This service involves physical processes spanning multiple time scales: hours (relative platform dynamics), minutes (link selection, atmospheric attenuation), milliseconds (atmospheric turbulence, platform disturbances), and nanoseconds (photon and bit transportation). The modified multi-scale method (MMM) was used to combine the physics of these processes and to model an end-to-end global FSO communication service between an airborne platform and a satellite constellation. The method provides a better understanding of physical interdependencies, allows performance analysis on multiple time scales, and enables valuable insight into where to optimize such a service. The results show realistic performance metrics when compared to other smaller-scale models and demonstrations. The MMM can be used as a mission performance indicator of an end-to-end satellite communication service.

The European Space Agency’s (ESA) Aeolus mission utilized a space-based light detection and ranging (LiDAR) instrument for atmospheric wind measurements. These measurements were derived from signals collected by accumulation charge-coupled Devices (ACCDs), which showed unexpected behavior in flight. During the nearly five-year operation of the exploratory mission, hot pixels in the silicon detectors appeared at an almost-linear rate, most of which exhibited random telegraph signal (RTS) behavior, contrary to predictions based on pre-flight testing. The discrepancy highlights a gap between ground-based radiation tests, typically conducted at room temperature, and in-flight silicon detector conditions of low temperature and low readout noise levels. In-flight dark current activation energies and RTS phenomena observed in ACCD pixels are analysed, including suspected electric field enhancement (EFE) effects. This study compares these in-flight anomalies with literature models that forecast displacement damage dose (DDD)-induced dark current rates to determine if space radiation effects could be the primary cause of the hot pixels.

High-Altitude Pseudo-Satellites (HAPS) platforms offer a cost-effective solution for remote connectivity with uninterrupted 24/7 availability, presenting a compelling alternative to conventional orbiting satellites. Integrating laser communication terminals onto HAPS platforms enhances their capabilities, enabling high bandwidth and long-distance remote connectivity. In this context, we present Skyline S2, a laser communication terminal for the Zephyr High-Altitude Pseudo-Satellite, a solar-powered platform developed by Airbus, operating in the stratosphere. The Skyline S2 Laser Communication Terminal (LCT), a collaborative development effort between Airbus Netherlands and partners, will enable a 1 Gbit/s inter-Zephyr bi-directional link, spanning distances of up to 100 km. We have designed a novel compact 40 mm aperture LCT that meets the stringent requirements concerning mass, size, and power consumption, while being capable of withstanding the harsh environmental conditions of ambient temperature and air pressure. This paper focuses on the early stages of development, during which prototype lab tests were conducted to mitigate potential risks. The fine steering mirror control performance, the resulting fibre coupling efficiency, and 1 Gbit/s free space communications link test results are discussed. Additionally, this paper summarizes the Skyline S2 design and outlines our roadmap for future developments and Zephyr flight experiments.

This paper intends to describe the activity of PPU (Power Processing Unit) anode supply robustness verification when subjected to Hall-effect thruster (HET) flicker phenomenon. Flicker is an instability of the operating point that can sometimes impact HETs, where the oscillation amplitude of the discharge current significantly increases. The robustness is studied theoretically with worst-case assumptions and a simulation tool is used to verify the conditions where coupling between flicker and propellant flow controller’s valve actuation occurs. Besides, a test campaign led in the frame of an Airbus Defence and Space (ADS) test campaign intended to validate a Plasma Propulsion Subsystem (PPS) product known as THruster Optimized and Reduced system (THORs) in 2019 provides data to consolidate the study. A custom electrical ground support equipment (EGSE) placed in parallel of the thruster’s anode is intended to simulate the flicker phenomenon from the PPU point of view. During this campaign, two distinct 300 W-class thrusters were used along with two distinct propellant flow controllers. The goals of these tests were to check if flicker could provoke instability in the fluidic chain regulation. Theoretical analysis and simulations are detailed to explain the observed phenomena, and some measurements results are shown and commented.

This paper intends to describe the activity of electrical chain modelling and validation by simulation of the MSR-ERO PPS subsystem. The electrical chain modelling comprises, on one hand, the thruster assembly modelling, the PPU-to-thruster-assembly modelling and the PPU-supplies modelling. On the other hand, the XFCU (Xenon Flow Control Unit) modelling is also comprised. The analyzes also focus on modelling of the thruster start-up waveforms as well as modelling of the beam-out event waveforms. Various simulations are performed to check the modelling with respect to expected electrical behaviour of the thruster. It shall be noticed that the activity is ongoing and will generate further updates as the execution of coupling tests and processing of the associated measurement data will be performed.

Stringent global regulations aim to reduce nitrogen dioxide (NO2) emissions from maritime shipping. However, the lack of a global monitoring system makes compliance verification challenging. To address this issue, we propose a systematic approach to monitor shipping emissions using unsupervised clustering techniques on spatio-temporal georeferenced data, specifically NO2 measurements obtained from the TROPOspheric Monitoring Instrument (TROPOMI) on board the Copernicus Sentinel-5 Precursor satellite. Our method involves partitioning spatio-temporally resolved measurements based on the similarity of NO2 column levels. We demonstrate the reproducibility of our approach through rigorous testing and validation using data collected from multiple regions and time periods. Our approach improves the spatial correlation coefficients between NO2 column clusters and shipping traffic frequency. Additionally, we identify a temporal correlation between NO2 column levels along shipping routes and the global container throughput index. We expect that our approach may serve as a prototype for a tool to identify anthropogenic maritime emissions, distinguishing them from background sources.

Studying and discussing boundary violations between people is important for potentially averting future harm. Organizations typically respond to boundary violations in retributive ways, by punishing the perpetrator. Interestingly, prior research has largely ignored the impact of sexual boundary violations and retributive dynamics on teams. This is problematic as teams provide an obvious setting not only to detect and discuss troubling behavior by peers, but also for learning how to prevent future harm. Therefore, in this study we explore team-level experiences regarding sexual boundary violations and organizational responses to these incidents. Drawing on an in-depth case study, our findings shed light on the profound negative consequences of a retributive organizational response to sexual boundary violations. Additionally, our findings show how a restorative approach, inviting teams to reflect on the violations and their impact, can help teams to recover. Our main contribution involves a model that demonstrates how the interplay between sexual boundary violations, retributive, and restorative organizational responses affects teams. This model shows how combining these responses can acknowledge distress within teams, heal relationships between team members through dialogue, and open up the possibility to learn from these events. This model extends prior research focusing on individual actions and outcomes regarding violations. Additionally, by combining retributive and restorative organizational responses in one model, we extend the literature on restorative organizational responses to boundary violations.

ESA’s Earth Return Orbiter (ERO) mission is a key element of the Mars Sample Return (MSR) campaign, a multi-mission international cooperation between ESA and NASA that is intended to bring pristine Martian samples back to Earth. The Earth Return Orbiter, for which Airbus Defence and Space France is Prime Contractor, is a heavy interplanetary spacecraft to be launched in 2027 on an Ariane 64 and will rely on electric propulsion to reach Mars, to support rendezvous manoeuvers to retrieve the samples in Mars orbit and then return to Earth. Multiple gridded ion thrusters of the ERO Plasma Propulsion Subsystem (PPS) will each be driven by an innovative European-made Power Processing Unit (PPU), capable of supplying over 8 kW of electrical power to each thruster whilst also controlling the associated propellant flow control unit. This state-of-the-art PPU developed by Airbus Crisa (Spain) benefits from the heritage of ESA’s BepiColombo mission and similar commercial products supplied for the telecom satellite market. Following an overview of the MSR-ERO mission and of the ERO Plasma Propulsion Subsystem architecture, this paper reports how the thruster power and thruster control requirements are addressed in the PPU design. The paper also provides a description of the hardware and operational features of the PPU. The philosophy of the PPS verification and validation plan, including PPU coupling tests with the gridded ion thruster, is also summarised.

This paper investigates the problem of optimal placement (position and orientation) of spacecraft thrusters, under fault diagnosability and fault recoverability constraints. Avionics equipment contamination and plume impingement are also considered. The goal is to find the thrusters configuration with the minimal number of thrusters required for a given spacecraft architecture, so that it is guaranteed that it is possible to equip the control unit with a model-based fault diagnosis and fault-tolerant control solution, able to accommodate any single thruster's fault. This includes total loss of controllability of the faulty thruster. The proposed solution is a model-based solution in the sense that it is based on the spacecraft attitude and translational dynamics. With the help of the zonotope concept and its so-called H-representation, it is shown that this problem can be formulated as a nonlinear constrained optimization problem, which can be solved efficiently using hybrid optimization techniques. The proposed solution is assessed on a generic spacecraft architecture that performs a proximity maneuver.

For already more than seven years, the Sentinel-1 C-band Synthetic Aperture Radar (SAR) mission has been providing indispensable information for monitoring bio-geophysical parameters at fine temporal and spatial scales. As many applications require backscatter datacubes as input, enormous amounts of data have to be radiometrically and geometrically corrected to be in a common, Earth-fixed reference system. Pre-processing workflows accomplishing this task have already been established and are implemented in several software suites. However, typically, these workflows are computationally expensive which may lead to prohibitively large costs when generating multi-year Sentinel-1 datacubes for whole continents or the world. In this paper, we discuss existing approaches for generating sigma nought and projected local incidence angle (PLIA) data and present simplifications of the overall workflow relying on the unprecedented orbital stability of Sentinel-1. Propagating orbital deviations through the complete Sentinel-1 pre-processing pipeline helped us to simulate and identify PLIA as a static layer per relative orbit. The outcome of these simulations also provided the necessary information to replace iterative root-finding algorithms for determining the time of closest approach (TCA), i.o.w. the azimuth index, with a linear one — at no expense of radiometric accuracy. All experiments were performed using an in-house developed toolbox named wizsard, which made it possible to speed up Sentinel-1 pre-processing by approximately 4–5 times with respect to the Sentinel Application Platform (SNAP). This could pave the way for producing quality-curated, large-scale backscatter datacubes at continental and global scales in acceptable time frames.