The Satellite Orbit DecAy (SODA) provides accurate forecasts of the effects of solar storms on low Earth-orbiting satellites, protecting them from crashes.
Scientists at Graz University of Technology and the University of Graz have developed a solar storm forecasting system. It is now officially part of the European Space Agency’s (ESA) Space Safety Programme.
Solar storms can often cause satellites to crash or knock them off their orbit. In early February 2022, a solar storm passing Earth caused the loss of 38 Starlink satellites.
The forecast service is freely available through the ESA Space Weather Service and offers a warning with a lead time of around 15 hours.
Solar orbiter – Nasa/ESA
Image credit: ESA/ATG medialab
Scientists have already studied the potentially dangerous effects of solar storms on satellite orbit.
SODA is based on the findings of SWEETS, a project funded by the Austrian Research Promotion Agency (FFG) that analysed atmospheric density data and real-time measurements of solar wind plasma and the interplanetary magnetic field to calculate the effects of solar events.
This research showed that solar storms can trigger satellite orbit decays of up to 40m for satellites at an altitude of 490km.
This is because, when a solar storms strikes the Earth’s magnetic field, it heats up the upper layers of the atmosphere. As a result, the atmospheric drag increases and causes satellites to lose speed and altitude.
Over the next two years, solar activity is expected to reach its maximum. In light of this warning, ESA has already increased the altitude of some of its satellites by a few kilometres to navigate this period safely. SODA is part of this effort.
The diagram shows the density increase in the atmosphere and the subsequent loss of altitude of a satellite at 490 km / ESA & NASA
Image credit: ESA & NASA/Solar Orbiter/EUI team – Data: TU Graz & Uni Graz
In order to develop SODA, the team, led by Sandro Krauss at Graz University of Technology, reviewed atmospheric densities over a 20-year period. For this purpose, they processed data from several low Earth orbit satellite missions, including CHAMP, GRACE, GRACE Follow-on and Swarm.
At the University of Graz, a group led by Manuela Temmer analysed around 300 solar storms catalogued between 2002 and 2017. These were based on measurements of the interplanetary magnetic field by probes at the L1 Lagrange point, located about 1.5 million kilometres from Earth.
SODA was developed from the joint analysis of these datasets.
“I am very pleased that, through SODA, TU Graz, together with Uni Graz and Seibersdorf Laboratories, is now the third Austrian institution to contribute to ESA’s Space Safety Programme,” said Krauss.
Temmer added: “Supplying ESA with this service is a welcome recognition of our work. I am also pleased that our partnership will continue as we work to improve SODA together within the framework of the FFG-funded project CASPER.
“It will help us to gain a better understanding of more complex solar storms, such as situations where two storms overlap on their way to Earth. We would also like to calculate the atmospheric density at altitudes of 450 and 400km – 490km is the lowest altitude we can calculate the density for so far. Since the field of solar storm forecasting is not yet very well researched, we are looking forward to some interesting insights.”
In 2020, Nasa and ESA launched the Solar Orbiter, the first satellite to provide close-up views of the Sun’s polar regions. It will also be able to see solar storms building up over an extended period from the same viewpoint, delivering data from parts of the Sun not visible from Earth.
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