Cluster mission set to end with reentry over South Pacific

On 8 September 2024, the primary of 4 satellites that make up ESA’s Cluster mission will reenter Earth’s ambiance over the South Pacific Ocean Uninhabited Space.

This marks the tip of the historic mission, over 24 years after it was despatched into space to measure Earth’s magnetic surroundings. Although the remaining three satellites will even cease making scientific observations, discoveries utilizing present mission knowledge are anticipated for years to come back.

This “focused reentry” is the primary of its type. ESA’s efforts to make sure a clear finish to the Cluster mission transcend worldwide requirements, making the company a world-leader in sustainable space exploration.

A lifetime monitoring space climate

Launched in 2000, Cluster has spent 24 years finding out maybe the one factor that makes Earth a novel liveable world the place life can thrive: its highly effective magnetic defend, the magnetosphere.

Like an infinite umbrella, the magnetosphere protects us from a lot of the driving rain of particles that the sun relentlessly sends in our route.

However gusts of this solar wind can nonetheless push via, sending bursts of energetic particles cascading in the direction of Earth’s floor. The most typical result’s the northern and southern lights (auroras), however extra hardly ever, these particles can lower our energy provides, disrupt radio communications, or harm satellites.

We name the affect of the solar wind on Earth’s magnetic surroundings “space climate.” And till Cluster got here alongside, space climate remained one thing of a thriller.

“For over 20 years, Cluster has proven us time and time once more how necessary the magnetosphere is in shielding us from the solar wind,” says Cluster Mission Supervisor Philippe Escoubet. “It has watched the results of solar storms to assist us higher perceive and forecast space climate.”

A zero-debris finale

Cluster was by no means designed to final this lengthy, nor was it designed for such a protected finale. It was initially launched on a two-year mission to check sun–Earth interactions. As a result of it was finishing up such spectacular and world-changing science, ESA’s spacecraft operators saved it going.

However all good issues should come to an finish, and Cluster’s time has lastly come. With this focused reentry, ESA is popping Cluster from a pioneer in space climate monitoring to a pioneer in mitigating space particles—two key parts within the company’s space security targets.

With out intervention, the 4 Cluster satellites would have reentered naturally in a much less predictable method, doubtlessly over a extra densely populated area. By focusing on the satellites’ reentries, ESA is taking the chance to make sure that Cluster’s demise does not contribute to the rocketing quantity of space junk in orbit round Earth.

Salsa’s final dance

Of the 4 Cluster satellites—nicknamed Rumba (Cluster 1), Salsa (Cluster 2), Samba (Cluster 3) and Tango (Cluster 4)—Salsa would be the first to make the leap again into Earth’s ambiance. It’s focusing on a particular area of the South Pacific Ocean that’s so far as doable from populated areas.

“Again in January we tweaked Salsa’s orbit to ensure that on 8 September it experiences its last steep drop from an altitude of roughly 110 km to 80 km,” explains Cluster Operations Supervisor Bruno Sousa. “This offers us the best doable management over the place the spacecraft will likely be captured by the ambiance and start to expend.”

Bruno’s crew is now watching the satellite from a distance. A focused reentry permits for a lot predictability within the reentry time and placement that there isn’t any want for additional maneuvers.

Regardless of being assured that no surviving fragments will fall wherever close to land, we nonetheless have little or no knowledge about how spacecraft behave as they cross via the decrease layers of the ambiance. We wish to know extra to foretell even higher the time and placement of satellite reentries and make sure the security of people on Earth.

ESA is contemplating observing Salsa’s reentry from an plane; this will likely be confirmed later in August. The 4 Cluster satellites are equivalent and so by watching them reenter the ambiance with barely completely different trajectories and in numerous climate situations, we might have the distinctive alternative to conduct a precious reentry experiment to check the break-up of satellites.

A brighter future

Cluster’s reentry follows these of ESA’s Aeolus and ERS-2 Earth remark missions. ESA is setting a precedent for a accountable method to decreasing the ever-increasing downside of space debris and uncontrolled reentries.

With this focused reentry, ESA is once more pioneering a brand new technique to scale back its environmental impression by disposing of its missions extra safely and sustainably than envisaged on the time of their design.

“By finding out how Salsa burns up, which elements may survive, for a way lengthy and in what state, we are going to study a lot about the right way to construct ‘zero-debris’ satellites,” explains Tim Flohrer, Head of ESA’s House Particles Workplace.

“The teachings realized from this exercise will assist flip focused reentries right into a protected and well-understood possibility for the disposal of different space missions in related orbits, equivalent to Smile and Proba-3.”

What’s subsequent?

Following Salsa’s reentry, the three remaining Cluster satellites will enter “caretaker” mode; whereas they won’t be making scientific measurements, operators will likely be monitoring them to attenuate the danger of collision with different satellites or Earth itself.

Bruno’s crew will regulate the orbit of Rumba (Cluster 1) in August 2024 in preparation for the same focused reentry in November 2025. They may then maneuver Samba (Cluster 3) and Tango (Cluster 4) in November 2024, prepared for Cluster’s last goodbye in August 2026.

On the finish of 2025, ESA plans to launch its subsequent mission to sort out Earth’s magnetic surroundings: the Photo voltaic wind Magnetosphere Ionosphere Hyperlink Explorer, or “Smile” for brief. A joint venture with the Chinese language Academy of Sciences, Smile will construct upon Cluster to disclose much more in regards to the advanced and intriguing magnetic surroundings surrounding planet Earth.