COLOGNE, Germany - Scientists at the German Aerospace Center (DLR) have developed a new forecasting and orbit-planning approach to improve satellite operations during severe geomagnetic storms, following space weather disruptions that affected the twin TerraSAR-X and TanDEM-X radar satellites in 2024.
Researchers from DLR's Space Operations and Astronaut Training facility presented the results at the International Symposium on Space Flight Dynamics (ISSFD) 2026 in Toulouse, France.
The work follows severe geomagnetic storms in March and May 2024 that caused operational disruptions for the TerraSAR-X and TanDEM-X missions. Although the satellites and their formation flight remained safe, changes in atmospheric conditions caused the spacecraft to move outside their required synchronization envelope, preventing the satellites from capturing synchronized radar imagery.
Geomagnetic storms occur when charged particles from the Sun interact with Earth's magnetic field, producing phenomena such as auroras while also affecting satellite operations and other space-based infrastructure.
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The incidents prompted flight dynamics specialists at DLR's German Space Operations Center to investigate the effects of space weather on orbital prediction and mission planning. The investigation concluded that more accurate forecasting of geomagnetic storms was needed to improve orbital predictions used in satellite operations planning.
TerraSAR-X and TanDEM-X operate in a Sun-synchronous orbit approximately 505 kilometers above Earth. At that altitude, DLR noted that atmospheric density is typically extremely low, at roughly 1 g/m³. During severe geomagnetic storms, however, the upper atmosphere can expand significantly, increasing atmospheric density by as much as a factor of 10 and creating greater atmospheric drag on satellites.
The effects were significant for the TanDEM-X mission because the two satellites operate in a closely coordinated helix formation. During portions of their orbit, the spacecraft approach within approximately 200 meters of one another and must maintain precise relative positioning to generate synchronized radar imagery.
Disturbances from density
According to DLR, the geomagnetic storms pushed existing atmospheric-density and orbital prediction models beyond the conditions for which they had previously been validated during a period of unusually intense solar activity. Increased atmospheric drag altered the satellites' relative positions enough to disrupt the synchronization required for joint radar observations.
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To improve operational resilience, DLR researchers analyzed geomagnetic storm events from recent years and compared observed satellite behavior with multiple atmospheric-density and space-weather forecasting models. The team also incorporated mission data from TanDEM-X to evaluate model performance.
The analysis resulted in a forecasting approach that combines three separate space-weather and atmospheric-density prediction models for mission planning and orbit determination.
DLR subsequently developed updated methods for orbit prediction, orbit control, and formation-flight monitoring based on the new forecasting framework. The upgraded flight dynamics processing chain was implemented for TanDEM-X operations in April 2025.
Predicting problems
According to DLR, the system successfully predicted the effects of severe geomagnetic storms that occurred in November 2025 and again in January and February 2026, allowing the radar satellites to continue operating without interruption and capture imagery as planned.
The agency said the findings could benefit operators of other low-Earth-orbit satellites subject to atmospheric-density variations caused by solar activity, where changes in atmospheric drag can significantly affect orbital predictions and mission planning.
