Decade-long survey shows effects of South Atlantic Anomaly on ESA’s Swarm satellites
A decade-long survey conducted by teams from ESA and Airbus reveals how space radiation over the South Atlantic Anomaly (SAA) affected the onboard memory systems of ESA’s Swarm constellation, a trio of satellites mapping Earth’s magnetic field since 2013.
Image credit: ESA/SSA
- Over 3 300 days of data from ESA’s Swarm satellites revealed how space radiation, intensified by SAA, disrupted onboard memory systems.
- The SAA, a weakened area in Earth’s magnetic field, emerged as the main source of radiation damage, exposing satellites to higher proton levels.
- Despite continuous exposure, advanced error correction systems and radiation shielding kept Swarm satellites operational and provided a foundation for improving future missions like Sentinel-6 and BepiColombo.
The Swarm mission, launched in 2013 to map Earth’s magnetic field, has revealed the challenges created by radiation over the South Atlantic Anomaly (SAA) in space systems.
Satellites in Earth’s orbit are continuously exposed to high-energy particles from cosmic and solar radiation which can disrupt onboard systems. To analyze these effects, a team from the European Space Agency (ESA) and Airbus conducted a study on ESA’s Swarm satellites.
What is Swarm’s mission?
The mission was launched in November 2013 and consists of 3 identical satellites orbiting Earth in formation.
The satellites map Earth’s magnetic field in 3 dimensions and have operated for 3 327 days under stable conditions. The mission’s focus on radiation effects sheds light on SEUs caused by transient electric charges as well as the potential for “stuck bits” and destructive “latch-ups.”
ESA implemented effective strategies to mitigate radiation risks during the mission.
Main systems were equipped with shielding to reduce exposure while error detection and correction mechanisms ensured reliable operations through continuous monitoring and adjustments.
Pre-mission simulations using ESA’s SPENVIS (Space Environment Information System) guided hardware design to withstand the challenging radiation environment.
The South Atlantic Anomaly and its role
The South Atlantic Anomaly (SAA) spans parts of South America and the Atlantic Ocean, representing a region where Earth’s magnetic field is weaker. The weakened field allows high-energy particles, mainly protons, to penetrate closer to Earth, exposing satellites to heightened radiation levels.
The anomaly increases the likelihood of disruptions to onboard systems for spacecraft operating in this area. The SAA is important because it influences both modern spacecraft and Earth’s magnetic environment.
The SAA has been closely monitored by Swarm satellites which have provided important data about its size, intensity, and long-term trends. The ESA’s earlier studies have shown that the anomaly correlates with the ongoing weakening of Earth’s magnetic field, adding urgency to research in this area. Swarm’s measurements have clarified how radiation levels in the SAA fluctuate and impact satellite operations.
“The starting point for our work on Swarm came through our looking into other sources of data, in a project called Conrad, for Continuous Feedback of Radiation Effects in Flight,” Marco Pinto of ESA’s Radiation and Component Reliability Section noted.
A decade of operations
The research focused on 3 memory components within the On-Board Computers (OBC) of Swarm satellites, mostly the Processor Module SRAM (PM-RAM), which played an important role in logging radiation-induced “Single Event Upsets” (SEUs). These components were designed to resist disruptions caused by space radiation by ensuring the satellites’ operational reliability.
The components experienced SEUs, where high-energy particles disrupted the Processor Module SRAM (PM-RAM) by flipping memory bits, leading to data corruption or performance anomalies in satellite operations.
“Single event effects do not typically interfere with normal mission operations, but it turns out they are all logged in the mission raw data. So why not investigate them, to compare them to our pre-mission modelling and see how effective our radiation hardness measures have been in practice?” Marco Pinto of ESA’s Radiation and Component Reliability Section stated.
The study found that while SEUs were expected their occurrence was less frequent than worst-case predictions. Most errors were observed in the SAA, a region where Earth’s magnetic field is weaker.
Heavy ions from galactic cosmic rays were also identified as another source of disruptions.
The Processor Module SRAM’s susceptibility to SEUs provided researchers with crucial points as it logged radiation events by enabling a detailed analysis of error patterns.
A zone of concern
The SAA, parts of South America and the Atlantic Ocean, emerged as the main source of radiation effects on the Swarm satellites. The region’s diminished magnetic field allows protons and other particles to penetrate and affect spacecraft systems.
Mapping SEUs across the satellites’ orbits clarified radiation’s influence on hardware performance.
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“The starting point for our work on Swarm came through our looking into other sources of data, in a project called Conrad, for Continuous Feedback of Radiation Effects in Flight. The most challenging part – to really turn the data into well-understood information – has been to liaise with the mission operators and check in with the industrial teams that put Swarm together, really working backward to get a close-up understanding of how the relevant systems work. But the results so far are well worth it!” Marco Pinto explained.
Radiation challenges on Swarm satellites
The research provided important observations about the effects of radiation on the Swarm satellites. Most errors originated from protons within the SAA while galactic cosmic rays were responsible for the remaining ones.
Variability in satellite performance was noted with the highest orbiting satellite experiencing fewer SEUs. The disparity may be because of hardware differences or localized variations in radiation levels.
Effective mitigation measures including radiation shielding and error correction systems, played a key role in maintaining satellite functionality.
The decade-long Swarm survey provides critical data to guide the design of radiation-resilient spacecraft.
“What is exciting is we can now apply the lessons learned to the management of Sentinel-6 and BepiColombo, for a start, and we can look into the operational archives of other missions, as a whole new source of data,” Marco Pinto remarked.
Lessons from the Swarm mission apply to other ESA missions using similar hardware such as Copernicus Sentinel-6 and BepiColombo. These missions can adopt refined operational strategies informed by Swarm’s decade-long data.
References:
1 Swarm vs. space radiation – the first 10 years – ESA – December 10, 2024
Rishika holds a Master’s in International Studies from Stella Maris College, Chennai, India, where she earned a gold medal, and an MCA from the University of Mysore, Karnataka, India. Previously, she served as a Research Assistant at the National Institute of Advanced Studies, Indian Institute of Science, Bengaluru, India. During her tenure, she contributed as a Junior Writer for Europe Monitor on the Global Politics website and as an Assistant Editor for The World This Week. Her work has also been published in The Hindu newspaper, showing her expertise in global affairs. Rishika is also a recipient of the Women Empowerment Award at the district level in Haryana, India, in 2022.
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