The European Space Agency (ESA) has bid farewell to the Cluster II spacecraft with a final set of commands to show that engineers are indeed human.

The four spacecraft have long been set for reentry, starting with Satellite 2, aka Salsa. The reentry occurred on Sunday, September 8, as planned. However, the mission controllers had time to upload one final command sequence before Salsa was destroyed in the Earth's atmosphere.

Former ESA Senior Advisor for Science & Exploration Mark McCaughrean shared the final moments in a post on Mastodon: "As a final action, a series of dummy commands were uplinked to Salsa, each containing the name of one of the active mission operations team.

"The spacecraft responded to each command, acknowledging receipt. Minutes later, it was gone, burned up in a blaze of glory in Earth’s atmosphere, 24 years after launch."

McCaughrean included images of the request and the current Cluster team, some of whom were likely still in full-time education when the mission launched.

Cluster, or Cluster II as it was known following the loss of the original spacecraft, was launched as two pairs of satellites on two Soyuz rockets from Baikonur. The first of the four was destroyed in the failure of the inaugural launch of the Ariane 5.

The four spacecraft were designed to fly in formation and study the Earth's magnetosphere. Thanks to some impressive creativity by the engineering team behind the spacecraft, the mission was extended from two years to well over two decades before the end finally came.

Three more Cluster spacecraft will reenter over the next two years, with ESA learning lessons from each of their experiences. Without intervention, the spacecraft could have reentered anywhere in an uncontrolled fashion.

ESA Director of Operations Rolf Densing explained why ESA decided to end the mission in this way: "Salsa's reentry was always going to be very low risk, but we wanted to push the boundaries and reduce the threat even further, demonstrating our commitment to ESA’s Zero Debris approach.

"By studying how and when Salsa and the other three Cluster satellites burn up in the atmosphere, we are learning a great deal about reentry science, hopefully allowing us to apply the same approach to other satellites when they come to the end of their lives."

Anthropomorphizing spacecraft is commonplace - XKCD arguably did it best - but the final act of the prodigiously successful Cluster mission has been to humanize the team behind the spacecraft and the effort required to keep the four spacecraft running in the face of increasing adversity.

No, you've got something in your eye. ®

https://www.theregister.com//2024/09/09/esa_cluster_salsa_farewell/