The first of a set of groundbreaking Cluster satellites is set for a controlled reentry next week.
The European Space Agency is paving the way in controlled reentry technology. ESA recently announced that plans to terminate the first of four Cluster satellites is about to come to fruition in early September, with the reentry of Salsa.
The Reentry
Salsa is one of four dance-themed Cluster satellites. The other three are Rumba, Samba and Tango. ESA controllers used the remaining thruster fuel on the spacecraft back in January to lower the perigee of the mission down to around 100 kilometers, which will assure destructive reentry for the 550 kilogram satellite over the South Pacific on or around September 8th. The area the satellite will meet its demise is known as ‘Point Nemo’ or the Pacific Ocean Uninhabited Area. The region has seen several large reentries over the years, including the Mir space station and ESA’s Automated Transfer Vehicle. The region will likely see the demise of the International Space Station sometime around 2030.
“By studying how Salsa burns up, which parts might survive, for how long and in what state, we will learn much about how to build ‘zero debris’ satellites,” says Tim Flohrer, (ESA-Space Debri Office) in a recent press release.
A Pioneering Mission
ESA designed the Cluster mission to explore space weather interactions with the Earth’s magnetic environment as the four spacecraft fly in a tetrahedral configuration through the planet’s magnetosphere. The four spacecraft fly out to a distant apogee of about 117,000 kilometers (over three times farther out versus geosynchronous orbit), and orbit the Earth once every 54 hours.
Launched in the summer of 2000, the Cluster satellites had a 5-year nominal mission, which lasted well over two decades. The missions have since proven to be pioneers in space weather research. The mission also escaped glitches and software failures over the years, including a bug requiring a “dirty hack” in 2010. Cluster II was also a replacement for the original set of Cluster satellites, which were lost on the inaugural launch of the Ariane-5 rocket on June 4th, 1996 from the Kourou Space Center. The mission ended in an explosion 37 seconds after liftoff.
Controlling Reentries
This sort of ‘targeted reentry’ for a long duration mission is one of the first of its kind for ESA. The zero-debris conclusion to the mission exceeds international standards. Furthermore, it also addresses issues surrounding the mitigation of debris in low Earth orbit. On Earth, ESA’s worldwide Estrack network will follow Salsa during its final orbits, and an airborne campaign is underway to spot the final reentry. ESA made a similar effort to image the Aeolus satellite in 2023, shortly before reentry.
Engineers will apply a similar technique to the SMILE (Solar wind Magnetosphere Ionosphere Link Explorer) and Proba-3 missions. These are also set to enter a similar far-ranging orbit around the Earth. SMILE is the follow-on mission to Cluster, and is launching in late 2025. ESA will launch the Proba-3 solar observatory next month. The mission will feature a free-flying, solar eclipsing disk.
You can spot the cluster satellites including Salsa on their final days. Salsa is COSPAR ID 2000-041A/26411in the NORAD satellite catalog, and listed in Heavens-Above. The satellites reach naked eye visibility on a good perigee pass.
After the demise of Salsa, Rumba will also reenter in November of next year, followed by Tango and Samba in August 2026.
While this is the ‘Last Dance’ for Salsa, the efforts to study space weather and come to terms with space debris continue.
Follow @ESAOperations and @ESA_Cluster on Twitter for the latest updates on Salsa leading up to reentry.