Multiple factors, including poor space weather conditions, led to the loss of 38 of the 49 Starlink satellites launched by Elon Musk’s SpaceX in February 2022, a new study has found.
In an era where the dependence on satellite-based services and operations is ever increasing, the loss of operational satellites could derail telecommunication, navigation and other vital operations on Earth, besides causing huge economic losses.
Starlink is a network of satellites operating to facilitate uninterrupted internet services in remote and inaccessible areas on Earth. These are small satellites launched at regular intervals into the Low Earth Orbit (LEO).
During the past two years, a team at the Centre of Excellence in Space Sciences India (CESSI) and the Department of Physics, Indian Institute of Science Education and Research (IISER) Kolkata, in collaboration with international scientists performed a detailed study to probe the possible contributors to the de-orbiting of Starlink satellites.
These solar physicists pinned down the prevailing space weather conditions, before and during the Starlink launch, to be moderate thereby increasing the mystery around the satellite losses.
Space weather is the environment around the Earth, other planets, and celestial objects in our galaxy which is largely controlled by the Sun’s activities. Space weather is affected by solar storms, coronal mass ejections and other ejectiles emerging from the Sun.
Around the Starlink satellite launch scheduled on February 3, 2022, the physicists said, space conditions were moderately disturbed, but these disturbances persisted over days. Based on Coronal Mass Ejections (CME) data obtained from the Solar and Heliospheric Observatory (SOHO) of the European Space Agency (ESA) and the NASA Wind spacecraft, it was found that three geomagnetic storms had emerged from the Sun in quick succession and disturbed the near-Earth space environment.
Speaking to The Indian Express, Dibyendu Nandi, head, CESSI, said, “These were moderate-intensity geomagnetic storms but together they stirred up persistent currents around the near-Earth atmosphere. These currents heated the upper atmosphere of the Earth which expanded and resulted in higher densities at LEO. Therefore, the newly launched satellites were subjected to higher-than-normal atmospheric drag or friction and they eventually deorbited to unrecoverable altitudes and were destroyed”.
According to Souvik Roy, a PhD student at CESSI, observations revealed that not only had the first solar storm reached just ahead of the Starlink launch, but two subsequent storms combined to cause persistent heating which lasted for up to four days, further dooming the just launched satellites.
The loss of 38 satellites caught the world’s attention in 2022 as the solar storms at the time were not thought to be potentially harmful and establishing a direct cause and effect was difficult.
For their detailed investigation, physicists at CESSI deployed computational modelling to link the passage of solar storms to increased currents and heating in the Earth’s space environment and the high orbital decay rates displayed by the Starlink satellites.
“With the help of data obtained from Swarm C, an ESA mission, we could conclude that Starlink satellites de-orbited to lower altitudes three times faster than expected,” said Yoshita Baruah, a PhD student of Physics at IISER Kolkata and the lead author of the recent paper published in the journal Space Weather.
Such unexpected orbital decay, Nandi remarked, is likely due to the larger surface area to mass ratio of the Starlink satellites, and added, “Our study gives us clues to improve the design of satellites such that they are more sustainable at low Earth orbits.”