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November 15, 2022 - Eruptions from the sun’s surface are common, occurring on average 2-3 times a day during the most active period of the 11-year sunspot cycle. The majority of these eruptions are not directed towards Earth. Those that are Earth-directed can create disturbances in Earth’s magnetic field, or geomagnetic storms. These storms produce the awe-inspiring northern lights, but can also result in significant disruptions to critical infrastructure. NOAA’s Space Weather Prediction Center (SWPC), home of the nation's official civilian space weather forecasters, issues real-time warnings and alerts to help customers mitigate impacts on the electric power grid, satellites, airlines, telecommunications networks, navigation systems (including GPS), and pipelines. The greatest concern for many customers is extreme geomagnetic storms, or G5 on NOAA’s Space Weather Scales. Fortunately, the G5 storms are not common events, occurring only 2-3 times on average over an 11-year solar cycle. Due to a rapidly growing commercial space industry, SWPC scientists are learning more about customer needs, and paying closer attention to minor geomagnetic storms that traditionally have had little effect on our lives and infrastructure on Earth and in space. In early February, 38 of the 49 Starlink satellites that SpaceX launched into very low-Earth orbit burned up as a result of a period of prolonged, minor geomagnetic storm conditions. A new study in Space Weather, a journal published by the American Geophysical Union, provides an analysis of space weather conditions that led to the Starlink satellite loss. Scientists from NOAA’s Space Weather Prediction Center and Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado at Boulder worked closely with SpaceX Starlink to co-author this study. They used observations from the Starlink satellites and forecasts and numerical simulations from NOAA to demonstrate the disturbance in the upper atmosphere and enhanced satellite drag conditions during the February event. This study confirms SpaceX’s preliminary analysis: high satellite drag conditions reduced satellite stability and made the orbit-raising process impossible. In response, the satellites quickly deorbited and ultimately burned up during reentry into the Earth’s atmosphere. |
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SWPC forecasters predicted the minor to moderate geomagnetic storms and issued watch, warning, and alert products beginning January 30 and continued to do so through February 5. However, the center doesn’t currently have warnings and alerts for satellite drag or neutral density predictions as described in the study, but has since prioritized the importance of this service following the satellite loss event.
With the commercial satellite industry establishing large constellations of small satellites and CubeSats – launching over 1,000 satellites per year – in low-Earth orbit, there is a growing customer need for information on the atmospheric density as it can have great impacts in lower orbit as witnessed with the Starlink satellite loss. The study recommends accurate forecasts of these events ahead of the onset of solar and geomagnetic storms, and identifies that it is “crucial for SWPC to establish suitable alerts and warnings based on neutral density predictions to provide users guidance for preventing satellite losses due to drag and to aid in collision avoidance calculations.” To provide suitable space weather predictions and warnings for this expanding industry, SWPC needs new observations and data to improve space weather forecast models.
The study identifies additional space weather forecast improvement services, and research areas that are critical to support the spacecraft industry at low-Earth orbits, including:
Better predictions of arrival time of Coronal Mass Ejection and magnitude and duration of geomagnetic activity. In addition, establishing the uncertainties and variability of solar wind/near-Earth interactions should be prioritized to provide probability forecasts of the responses at Earth.
Computationally efficient data-assimilation techniques to utilize the large volume of on-orbit neutral density observations will allow SWPC to improve neutral atmosphere nowcasts and produce better forecasts.
Improved processes in the satellite industry to incorporate space weather information and neutral density models that better capture space weather responses into satellite design and operations.
The study also notes that insufficient measurements between the sun and Earth, limitations in SWPC modeling tools, and knowledge gaps in space physics all lead to prediction errors on geomagnetic storm timing and intensity.
The study found that SWPC’s physics-based numerical model, called WAM-IPE, captured the enhanced neutral density environment responsible for the Starlink satellite loss event, out-performing the empirical model used by the Starlink team for their analyses. Collaborating with Starlink and others in this growing industry, SWPC will incorporate design changes to the WAM-IPE to make the model more useful to both industry and government interests in low- and very low-Earth orbits. In addition, SWPC is developing a neutral density product with a comprehensive, satellite-focused webpage for the spacecraft industry to access model outputs and forecasts. These improvements will take place in mid-2023.
“This study demonstrates the benefits that can come from collaborative work between government and industry,” said Tzu-Wei Fang, Ph.D., lead author of the study and space scientist at NOAA Space Weather Prediction Center. “The free exchange of model and satellite data and close interaction between SWPC and the Starlink team have enabled us to identify the quantitative impact of space weather events on these satellites, which help us to quickly prioritize our tasks to improve our space weather models and design the operational products that will better meet the needs of modern space commerce.”
Further, the Starlink team has implemented system upgrades to ensure future low insertion missions can accommodate the satellite drag given the anticipated increase in solar and geomagnetic activity as we approach the maximum of Solar Cycle 25, the study said. SpaceX has successfully achieved more than 60 satellite launches since November 2019, specifically for deploying the Starlink system. The earlier launches took place during a period of quiet space weather conditions compared to what was observed in early February.
This event renews the need for an enhanced space weather observing and forecast system that not only focuses on capturing massive Coronal Mass Ejections, like that associated with the Carrington Event, but also on the minor to moderate space weather events that have been happening much more frequently in recent months. These minor to moderate events, similar in magnitude to the Starlink loss event, will increase as we move deeper into Solar Cycle 25. It’s important to improve space weather forecast capabilities and services before the solar maximum in 2024-2025.
