The ability of space-based infrastructure to provide essential and sustained benefits to humanity in critical areas such as communications, Earth observation, technology development, navigation, and space exploration is increasingly threatened by the growing amount of orbital debris. A deliberate, urgent, and sustained effort must be made to resolve the problem of space debris and to ensure a risk-free utilisation and sustainability of the space environment. In this paper, we review the concept and appropriate technologies for orbital sustainability in low Earth orbit (LEO) and provide model-based space situational awareness (SSA) for LEO debris. We simulate the long-term evolution of the orbital decay of eight catalogued LEO objects due to space weather-enhanced atmospheric drag, as a function of solar-geophysical indices during Jan-Jun 2024, using the ephemeris data-assisted calibration (EDAC) method. The simulated mean heights and orbit decay rates of the objects compared well with their historical orbital data, although slight deviations were observed depending on the objects’ altitudes. The objects between 500 and 600 km altitude experienced an 8-fold drag effect compared to objects between 600 and 700 km altitude. We also investigated the short-term enhancement of aerodynamic drag during the severe geomagnetic storm of 10–11 May 2024 and found that the storm increased the objects’ orbit decay rates by 233–266% during its main phase, with up to 7-fold relative impact for a group separation of about 60 km. The impact levels were strongly influenced by storm-driven thermospheric density enhancements at the object altitudes, in combination with object-specific orbital dynamics, ballistic properties, and operational characteristics. We also showed that the long-term evolution of atmospheric drag-induced orbital decay on the objects obtained from both EDAC simulated results and the objects’ historical data were also consistent with the signature of solar cycle variation. The results demonstrate significant improvement in drag modeling and that the simulation of a long-term drag impact for maintaining reliable SSA for LEO objects is achievable.

Space weather phenomena, which impact navigation and communication systems of our modern technological infrastructure, can influence flight operations affecting safety or efficiency of aviation. This study investigates these impacts with a comprehensive survey of industry professionals including 13 pilots. The results indicate that a significant amount of participants is familiar with space weather, but that specific impacts and potential risks are less understood. The results also show that communication between aviation stakeholders and space weather service providers in particular is perceived as lacking. This in turn has a negative impact on other issues, such as finding and using appropriate space weather services already in operation. The implications are discussed, highlighting a need for better communication between space weather service providers and aviation stakeholders, better space weather risk awareness, more in-depth space weather training and protocols as well as application-oriented space weather services. Thus, actionable instructions are provided to strengthen aviation’s resilience to space weather events and to ensure dependable systems.

The Relativistic Electron Alert System for Exploration (REleASE) forecasting metric, developed by Posner (2007), utilizes electron data collected by the Electron Proton Helium Instrument (EPHIN) aboard the SOHO spacecraft. Our project aims to enhance the probability of detection, decrease the false alarm rate and extend the warning time by implementing various remote sensing techniques. These include automatic flare detection and localization, as well as automatic radio burst detection using the ROBUST algorithm developed at the University of Graz. Historically, a range of diagnostics for Solar Energetic Particle (SEP) events based on radio observations from Earth has been developed since the 1960s, which are to some extent utilized in contemporary prediction models. These diagnostics span from the occurrence of long-lasting broadband radio emissions (cm-m waves) to the spectra of microwave bursts (mm-cm waves). The presence of radio emission at meter wavelengths (e.g., type III bursts) is crucial, since it indicates particle injection into the high corona, but is absent in confined flares, where no particles escape from the active region and no CME is available to accelerate particles higher up.Moreover, our project explores the extent to which diagnostics across diverse frequency ranges can enhance the REleASE system. Initial results of this integration and its impact on the accuracy of SEP event forecasting will be presented.

Since its launch in 2013, ESA’s Swarm satellite constellation has pushed the frontiers of space weather research and monitoring by means of its broad spectrum of high-quality experiments on-board. Particularly, Swarm observations are being used to globally characterize small- to mid-scale perturbations in the topside ionosphere that may cause severe amplitude and phase scintillations of trans-ionospheric radio signals. Ionospheric scintillation can cause radio signal outage, as well as disruption of modern technological systems used for telecommunication, navigation and remote sensing. While performing the Swarm DISC project “Monitoring of Ionospheric Gradients at Swarm (MIGRAS)”, the MIGRAS team has profited from the close orbits and synchronization of Swarm satellites Alpha (A) and Charlie (C) to develop two new products that focus on the monitoring of small- to mid-scale plasma density irregularities with horizontal spatial scales in the order of about 100 km - the electron density (Ne) Gradient Ionospheric indeX (NeGIX), and the Total Electron Content (TEC) Gradient Ionospheric indeX (TEGIX). NeGIX estimates spatial Ne gradients using Langmuir probe measurements, and TEGIX estimates spatial TEC gradients using GNSS Precise Orbit Determination (POD) data of Swarm. In this work, we provide a comprehensive analysis of the capability of these two novel Swarm data products to characterize the perturbation state of the ionosphere at different geographic locations and conditions of geomagnetic activity. Our analysis covers the whole period of available Swarm observations to quantitively describe expected signatures of ionospheric variability, e.g. gradients at sunrise and sunset time, or equatorial crests. The analysis concentrates also on events of perturbed geomagnetic conditions to compare the performance of NeGIX and TEGIX with existing ground-based indices (e.g. GIX) and Swarm products (e.g. IPIR). Moreover, these indices have been developed technically compatible with Swarm’s and DLR’s operational data services. Therefore, our analysis validates and discusses their applicability for space weather science and purposes. Acknowledgement: The work is funded by the MIGRAS (Monitoring of Ionospheric Gradients At Swarm) project under the Swarm DISC Subcontract Doc. no: SW‐CO‐DTU‐GS‐133, Rev: 1, 13 September 2022.

The detection, monitoring, and characterization of ionospheric perturbations are key areas of space weather research due to their significant impact on man-made technological systems. The European Space Agency’s (ESA) Swarm mission has provided high-quality data and services for more than 11 years, enriching our understanding of solar, magnetospheric, thermospheric, ionospheric, and atmospheric processes, as well as their coupling and effects on human activities. As part of the Swarm Data, Innovation, and Science Cluster (DISC) project “Monitoring Ionospheric GRAdients at Swarm (MIGRAS)”, we have developed two novel Swarm data products to study the state and dynamics of the ionosphere at Swarm height and medium scales – in the order of 100 km. We introduce and validate the electron density spatial gradient index, NeGIX, and the total electron content (TEC) gradient index, TEGIX. We leverage the near-polar, parallel orbits of Swarm A and C to combine data with a resolution of 0.5° in latitude along the satellite tracks. NeGIX uses electron density measurements from the Langmuir Probe experiment onboard Swarm A and C, while TEGIX uses Precise Orbit Determination (POD) data from the Swarm TEC product. We validate these indices for both quiet and perturbed geomagnetic conditions, and further comparison is made with the Swarm Ionospheric Plasma IRregularities (IPIR) product and the ground-based Gradient Ionosphere indeX (GIX). The zonal component of the NeGIX and TEGIX gradients, and particularly their meridional component, clearly identify ionospheric perturbations in the selected case studies. These indices have a high potential for detecting ionospheric perturbations during storm events and provide valuable information about their dynamical evolution. It is expected that NeGIX and TEGIX may essentially support ionospheric research, practical applications, and low-latency monitoring services.

The Mother's day storm from 10-13 May 2024 is one of the most extreme space weather events recorded in recent decades and triggered a strong ionospheric response with various impacts on communication and navigation systems. In this study the impact on the aviation sector, and more specifically air traffic management, is investigated with Automatic Dependent Surveillance-Broadcast (ADS-B) data from the OpenSky network. For that purpose, the event is presented with solar radiation and wind observations to describe the space weather conditions. Further, the spatial and temporal variations of the ionospheric response over Europe are analyzed with total electron content (TEC) maps and the performance of positioning via Global Navigation Satellite Systems (GNSS) is examined with 100 reference stations. These analyses show well-known space weather impacts including TEC perturbations, sudden ionospheric disturbances, signal-loss and degraded GNSS performance. Consequently, these effects are also expected for the GNSS positions transmitted via ADS-B, and the analysis confirms that a higher frequency of such anomalies occurs along flight tracks during the event (increase of up to 2.55%). These anomalies may manifest as data gaps or as position errors of various types, which in turn could decrease the visibility and awareness of participants in shared air spaces. The correlation between space weather and anomalies in ADS-B, as also shown in preceding studies, is thus further substantiated and motivates for follow-up research that combines application-specific data like ADS-B with commonly used ionospheric observations.

A major impact on human and robotic space exploration activities is the sudden and prompt occurrence of solar energetic ion events. In 2023 and 2024, {STEREO} is approaching the Earth from a behind position, soon passing Earth inside its orbit and thereafter moving ahead of Earth. {STEREO} thus offers several unique opportunities during this passage. In the period from June 1 to November 1, 2023, 5 {SEP} events have been measured that cause proton fluxes of above 25~MeV to rise above 0.1 /(cm$^2$\; s\; sr\; MeV). Taking into account systematic and statistical uncertainties of the particle measurements we find a good agreement between both spacecraft.The SOHO/EPHIN and STEREO/SEPTproject is supported under Grant 50~OC~2102 by the German Bundesministerium für Wirtschaft through the Deutsches Zentrum für Luft- und Raumfahrt (DLR). This study has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 101004159 (SERPENTINE).

Space weather events can disrupt satellite navigation, potentially compromising also the accuracy of real-time flight tracking via Automatic Dependent Surveillance-Broadcast (ADS-B). This in turn could limit the situational awareness of pilots and reduce the efficiency of the air traffic management. This study shows these impacts of space weather for selected flight tracks during the 9 February 2024 solar flare and compares the ADS-B reported data with solar flux and total electron content measurements. Gaps and position errors in ADS-B reported data, which reduce the visibility of the aircraft to other participants in the airspace, correlate well with the flare peaks and corresponding ionospheric disturbances showing a clear impact. These first results are further used to discuss appropriate space weather products for the pilot briefing as well as in-flight monitoring, since existing approaches can be extended with the ADS-B information to provide more precise space weather predictions.

Total electron content (TEC) maps are essential for understanding the temporal and spatial variability of the ionosphere, which is of particular importance during the current solar cycle with its multitude of extreme space weather events. This study presents an improved method for the global TEC map of the Ionosphere Monitoring and Prediction Center (IMPC) by incorporating an algorithm based on radial basis function interpolation. By refining the generation of the global TEC map, the accuracy and granularity of ionospheric gradients, which occur during these events, are significantly improved. The validation through comprehensive comparisons with the established TEC map and the global TEC map of the Technical University of Catalonia (UPC) confirms that the new algorithm outperforms previous results. Thus, a more robust framework for ionospheric research and application is provided. TEC gradients derived from the improved TEC maps are important for understanding the space weather impact on Global Navigation Satellite System (GNSS) applications. The new results can support these with more reliable and consistent predictions by accurately capturing these gradients.

Safe and efficient management of the constantly growing air traffic is an important task. For that reason, the international civil aviation organization (ICAO) approved Automatic Dependent Surveillance (ADS) system is used to share information (e.g. position, altitude and speed) between aircraft and air traffic control units. This improves the situational awareness and visibility of aircraft but also the environmental impact and air space capacity. Both applications of ADS, Broadcast (B) and Contract (C), rely on satellite-based communication and navigation services, which can be significantly disturbed by space weather impacts (e.g. loss of the signal and position errors). Therefore, related impacts are also observed for ADS records especially during extreme space weather events. We will present such impacts for both, ADS-B and ADS-C, with first results from an analysis covering periods with solar flares and geomagnetic storms. We will also discuss the challenge of differentiating space weather impacts from other influences. Finally, we will give an outlook how monitoring these impacts could contribute to space weather services.

Reaching the maximum of solar cycle 25 the influence of space weather is becoming increasingly critical, with phenomena like solar flares and geomagnetic storms occurring more frequently, affecting satellite technology, aerospace operations, telecommunications, and navigation systems more severely. The DLR Institute for Solar-Terrestrial Physics in Neustrelitz (DLR-SO) studies these impacts on critical infrastructures. Central to these activities is the Ionosphere Monitoring and Prediction Center (IMPC) which provides near real-time monitoring and prediction capabilities for space weather impacts, enhancing system resilience and reliability. It leverages advanced instrumentation and data processing technologies, including GNSS-based remote sensing and ionospheric modeling. IMPC instruments like the Global Ionospheric Flare Detection System (GIFDS) and eCALLISTO offer comprehensive space weather data assets. Integrated into international networks, the IMPC contributes to a global effort to understand and mitigate space weather impacts to protect and improve our technology and its operational performance during space weather events.

Surveillance and route conformance monitoring for air traffic are supported by information shared via Automatic Dependent Surveillance Contracts (ADS-C). This includes parameters for aircraft position and altitude, which are applied to trigger event reports if the observed values exceed defined limits (e.g. due to offsets). A rate of such event reports compared to the number of ADS-C records is calculated in the present study for the New Zealand airspace and analyzed via a composite analysis to describe variability according to local time, latitude and distance. Since this analysis indicates the impact of large-scale processes, weather and space weather phenomena are investigated in more detail. Flight tracks are presented in combination with tropospheric and ionospheric parameters to discuss increased rates of event reports via disturbances. Further categories of geometry, weather and space weather are identified from these results and the corresponding impacts are summarized in an overview. The occurrence of event reports can be attributed to both, tropospheric and ionospheric disturbances, and a correlation to solar flux and geomagnetic activity measurements is indicated. Thus, the study provides a first insight into the variability of ADS-C records with respect to weather and space weather in New Zealand airspace.

To understand the global response of thermospheric-ionospheric (TI) parameters to variations in solar irradiance measurements from the Global-Scale Observations of the Limb and Disk (GOLD) ultraviolet imaging spectrograph, solar radio flux F10.7, predictions from the Coupled Thermosphere Ionosphere Plasmasphere electrodynamics (CTIPe) model, and International Global Navigation Satellite System Service total electron content maps (TEC) have been used. Various parameters such as GOLD O/N-2, O-2, and the nighttime peak electron density (Nmax) have been compared with the CTIPe model simulations. The GOLD observed Nmax shows a number of significant features including a winter anomaly and an equatorial ionization anomaly. The comparison with solar proxies showed that the GOLD Q(EUV) correlates very well with the EUV observations compared to the F10.7 index. The study also examined the relationship between the solar proxies and Nmax on different time scales and found that Nmax responded significantly to Q(EUV) at both medium- and long-term timescales. Furthermore, a low correlation between Nmax in the equatorial region and solar proxies was found. A delayed ionospheric TEC response against solar flux variations within the 27-day solar rotation was investigated. This ionospheric delay of TEC with respect to solar flux was observed to be less than 1 day, which was reproduced in model simulations. The current study has shown that the GOLD observations can be used to investigate the delayed ionospheric response and to gain a better understanding of the influence of solar activity on the TI system.

The outer boundary of the plasmasphere, the plasmapause, is characterized by a sharp electron density gradient that changes under varying space weather conditions. We developed a new model, called the Neustrelitz/ESOC PlasmaPause Model (NEPPM), for providing plasmapause location in terms of L-shell utilizing electron density measurements from the Van Allen Probes from 2012 to 2018 and the IMAGE satellite data from 2001 to 2005. Both datasets were preprocessed, and algorithms were developed for the automatic detection of plasmapause location Lpp where L denotes the McIlwain parameter. The suggested model provides a simple ellipse-based approach determined by the semi-major axis, the eccentricity, and the orientation angle of the semi-major axis. The modelled Lpp varies as a function of the Dst index and magnetic local time MLT. The NEPPM results are compared with the Global Core Plasma Model (GCPM). The plasmapause bulge in the evening hours follows the level of geomagnetic activity. The NEPPM will complete the NPSM (Neustrelitz PlasmaSphere Model), which was derived from dual-frequency GPS measurements onboard the CHAMP satellite mission.

In the recent years we have witnessed unprecedented increase in both active and expired space missions (debris) – a scenario, if continued, that can lead to generation of even more debris through possible ‘satellite-satellite’ collision, ‘satellite-debris’ collision and/or ‘debris-debris’ collision (Kessler effect), especially in the heavily used low Earth orbit (LEO). Consequently, the possibility of a risk-free utilization and sustainability of space is significantly threatened because of the predisposed risk to both manned (e.g., the ISS) and unmanned active spacecrafts in this region of space. Space weather-enhanced atmospheric drag (and consequent increase in the rate of orbit decay) makes the risk even more worrisome. In this work, we investigate atmospheric drag effect on the trajectory of identified LEO objects (debris) during the 25th solar cycle and perform collision risk analysis for the International Space Station (ISS) operating at h≈415 km. We present relevant results and observations from this effort that are beneficial for orbit sustainability in LEO.