The Aeolus wind mission, a remarkable project from the European Space Agency (ESA), has officially come to an end, marking a new standard in satellite reentry safety measures. The visualization of a satellite disintegrating upon reentering the Earth’s atmosphere represents this groundbreaking achievement.
The Aeolus wind mission, surpassing scientific expectations and outliving its planned orbit lifespan, is celebrated as one of the most triumphant Earth observation ventures by the ESA. Its conclusion is noteworthy due to the innovative efforts of ESA’s mission control team, who steered this exceptional satellite towards a safe reentry into Earth’s atmosphere.
The Aeolus satellite made its reentry into Earth’s atmosphere over Antarctica on July 28 at approximately 21:00 CEST, as confirmed by US Space Command.
The Aeolus mission has provided critical and precise insights into global wind patterns, in addition to detailed information about aerosols and clouds. It has significantly contributed to advancing our knowledge of atmospheric dynamics, and has been instrumental in enhancing weather forecasts and climate research. Credit: ESA/ATG medialab
Following a set of intricate maneuvers, the Aeolus satellite’s orbit was reduced from an initial altitude of 320 km to a mere 120 km for reentry and subsequent disintegration in the atmosphere.
These maneuvers, the first of its kind in assisted reentry, strategically positioned Aeolus so that any remnants that didn’t disintegrate would fall along the satellite’s projected Atlantic trajectories.
Modern satellite missions are designed following rules mandating minimization of damage risk upon reentry. Typically, this is achieved through ensuring most of the satellite disintegrates upon reentry or through controlled reentry at their lifecycle’s end. However, during Aeolus’s conceptualization in the late 1990s, these regulations were not yet established.
Assisted reentry illustration for Aeolus. Credit: ESA/J. Mai
Had there been no intervention, Aeolus, having depleted its fuel, would have naturally reentered Earth’s atmosphere within a few weeks, with the reentry location being uncontrolled.
Although fragments of satellites and rocket components fall back to Earth approximately weekly, and seldom cause any harm, the risk of Aeolus causing damage was minimal. The probability of being hit by debris is three times less than that of being hit by a meteorite.
Regardless, the ESA outperformed expectations with Aeolus, pioneering a new method of assisted reentry to further enhance safety.
Planning and conceptualizing for a satellite to perform tasks it was not initially designed for was a considerable undertaking.
Aeolus’ reentry key stages. Credit: ESA
In the final week, the team comprising spacecraft engineers, flight dynamics experts, and space debris specialists at ESA’s ESOC mission control center in Germany put their plans into action. They utilized Aeolus’s residual fuel for a series of burns to lower the satellite into the optimal reentry position.
The team was successful in this endeavor, with Aeolus’s reentry adhering to current regulations.
Rolf Densing, ESA’s Director of Operations, stated, “The team’s achievement is significant. The maneuvers were intricate, Aeolus was not designed to execute them, and there was always the risk that this initial assisted reentry might fail. While Aeolus reentry was always low risk, we wanted to push the boundaries and further reduce the risk, demonstrating our commitment to ESA’s Zero Debris approach. We have gleaned a wealth of knowledge from this success, which could potentially be used for other satellites ending their lives, launched before current disposal measures were established.”
The successful assisted reentry is a facet of ESA’s broader commitment to the long-term safety and sustainability of space activities. By 2030, all ESA missions will comply with the ‘debris neutral’ mandate, as part of the Zero Debris Charter, ensuring readiness for not only current regulations but also future stringent rules.
With initiatives ranging from deorbiting kits launched with missions for safe reentry, to significant missions like Clearspace-1, designed to retrieve stranded spacecraft in orbit and technologies to limit ground risks, ESA is at the forefront of sustainable space.
Aeolus: the mission deemed impossible
Aeolus has been a mission full of challenges – its trailblazing laser technology required years to develop. However, after several setbacks, Aeolus was finally launched in 2018. Its mission to profile Earth’s winds turned it into one of ESA’s most successful Earth observation research missions.
Aeolus carried Aladin, Europe’s most advanced Doppler wind lidar sent into space.
The device emitted ultraviolet light pulses towards Earth’s atmosphere which then reflected off air molecules and atmospheric particles such as dust. The minimal amount of light that scattered back to the satellite was captured by a large telescope.
The Doppler shifts in the return signals enabled the calculation of the horizontal wind speed within the lowermost 30 km of the atmosphere. This feature made Aeolus the inaugural satellite mission to deliver global wind profiles.
The mission, an ESA Earth Explorer research mission, was primarily aimed at proving the feasibility of this technology – but its achievements went far beyond that.
Simonetta Cheli, ESA’s Director of Earth Observation Programmes, said, “Aeolus has been extraordinarily successful. Indeed, the technology was challenging to develop but the returns have been massive. Not only did it contribute to climate research, but its data were also operational in weather forecasts, which proved crucial during the Covid lockdown when aircraft, carrying weather instruments, were grounded. According to a 2022 report by London Economics, Aeolus also yielded real economic benefits – up to €3.5 billion throughout the mission’s lifespan. We take immense pride in Aeolus and all those who made its development, orbital lifespan, data use, and safe termination possible. Now, we shift our attention to its successor, Aeolus-2, an operational meteorological mission we are developing with Eumetsat, Europe’s Organisation for the Exploitation of Meteorological Satellites.”
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Frequently Asked Questions (FAQs) about Satellite reentry safety measures
What was the purpose of ESA’s Aeolus wind mission?
The purpose of ESA’s Aeolus wind mission was to provide timely and accurate profiles of global winds, as well as gather information on aerosols and clouds. The mission aimed to advance our understanding of atmospheric dynamics and contribute to weather forecasts and climate research.
How did the Aeolus mission end?
The Aeolus mission ended with a historic assisted reentry into Earth’s atmosphere. The satellite’s orbit was lowered through a series of complex maneuvers, and it safely burned up during reentry, setting new safety benchmarks for satellite disposal.
What made the Aeolus mission unique?
The Aeolus mission was unique due to its pioneering use of laser technology called Aladin, which enabled the satellite to measure horizontal wind speed within the lowermost 30 km of the atmosphere on a global scale. It was the first satellite mission to provide such detailed wind profiles.
What was the significance of the assisted reentry?
The assisted reentry was significant because it was the first of its kind and involved positioning the satellite so that any remnants that didn’t disintegrate would fall within planned Atlantic ground tracks, reducing the risk of causing harm on Earth.
How does ESA ensure long-term safety and sustainability of space activities?
ESA is committed to long-term safety and sustainability in space through initiatives like the Zero Debris Charter. By 2030, all ESA missions will be ‘debris neutral,’ focusing on technology readiness for future stringent regulations to minimize space debris.
