\tSpace Safety<\/p>\n
\t\t\t\t\t\t28\/08\/2026
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The final two of ESA’s pioneering Cluster<\/a> spacecraft, Samba and Tango, will end their journeys as they burn up in our atmosphere on 31 August and 1 September respectively. Their targeted reentries<\/a> mark the end of a mission that has transformed our understanding of Earth’s magnetic environment. The final moments also offer a rare scientific opportunity for reentry observations from a plane.<\/p>\n \u201cWhen a spacecraft reenters the atmosphere, it experiences extreme forces. Temperatures soar, materials melt and vaporise, and the spacecraft gradually breaks apart. But how exactly?\u201d says Stijn Lemmens, senior space debris mitigation analyst at ESA. \u00a0<\/p>\n \u201cWe need to understand better how they disintegrate to inform the design of spacecraft that can burn up completely, reducing the risk on the ground, while we also aim to prevent pollution of the atmosphere.\u201d<\/p>\n \t\t\t\t\t\t\tThe ROSIE Samba and Tango team are setting up their instruments on the plane, preparing for the observation campaign in Bankstown, Australia<\/a><\/p>\n Engineers can simulate aspects of these conditions on the ground, but reproducing the exact environment of a real atmospheric reentry is not possible. That\u2019s why ESA, as part of its space safety activities<\/a>, is sending a plane to observe the last two Cluster reentries from below for a repetition of the first airborne observation experiment for Cluster\u2019s Salsa<\/a> in 2024.<\/p>\n \tCollecting valuable reentry data <\/p>\n The team will be collecting as much reentry data as possible while the satellites are reentering Earth\u2019s atmosphere about 24 hours apart in a remote location over the South Pacific Ocean.<\/p>\n In January, Cluster\u2019s operations team already set the Cluster satellites on their trajectories for \u2018targeted reentries<\/a>\u2019 to ensure a precise location that is both remote, yet just reachable for observations with a small plane coming from Tonga.<\/p>\n \t\t\t\t\t\t\tThe trajectory of Samba and Tango has them safely reenter over a remote corner of the South Pacific Ocean where our plane can meet them<\/a><\/p>\n The Cluster spacecraft are unusual because they are not reentering due primarily to atmospheric drag like most satellite circling Earth. Instead, as they fly out far on a highly elliptical orbit, their return is driven by long-term gravitational interactions with the Earth, Sun and Moon, making it possible to plan and target their reentries.<\/p>\n \t\t\t\t\t\t\tThe highly elliptical orbit allowed for the precise timing of the satellites\u2019 reentry, for a safe disposal in a location that also enabled observation by plane<\/a><\/p>\n Now, the ROSIE airborne observation campaigns, led by Astros Solutions<\/a>, will take to the skies from Tonga on 31 August and fly over the ocean for hours to get to the reentry location to witness Samba\u2019s demise. Then, they\u2019ll return to Tonga to rest and regroup before doing it once more for Tango the very next day.<\/p>\n \u201cIt\u2019s quite the logistical challenge. The plane has to be at exactly the right time and place, facing the right way, safely on the edge of the no-fly zone. Everything has to come together in exactly the right moment. To capture the reentry, the team will be using a set of instruments, 30 in total, improved from the ones we used during Salsa’s reentry,\u201d says Ji\u0159\u00ed \u0160ilha from Astros Solutions.<\/p>\n \t\t\t\t\t\t\tStefan L\u00f6hle and David Leiser (University of Stuttgart) setting up their instruments in front of the plane windows<\/a><\/p>\n \u201cWe have done it once before \u2013 a large part of the value of the campaign is the repetition for a strong data set \u2013 but now it is a double challenge. To do this twice in 24 hours will ask the absolute maximum from all our team members as well as our equipment. The ROSIE-Samba\/Tango missions are a joint effort of academic partners from University of Stuttgart (IRS\/HEFDiG), Comenius University in Bratislava (CUB) and industrial partners from Hypersonic Technology G\u00f6ttingen (HTG), Zafiro Systems (Zafiro) and Astros Solutions in close cooperation with the European Space Agency.”\u00a0<\/p>\n Multiple of the instruments will be capturing spectral data, looking for the tell-tale signatures of materials dissolving that allow to remotely register what materials are melting and when. These sensors are supported by visual and infrared cameras.<\/p>\n \tSalsa\u2019s lessons learned<\/p>\n \u201cWitnessing the first Cluster-2 satellite Salsa reenter has already produced intriguing results. For instance, we realised there was a mismatch of up to 20% with the expected atmospheric density, highlighting how uncertainties in the upper atmosphere can affect reentry forecasts,\u201d says Stijn Lemmens.<\/p>\n \u201cAnd for the break-up itself, this seemed to start slightly earlier than models predicted. Was this an anomaly, or an indication that our understanding needs refinement? Observing Samba and Tango under similar conditions will help answer that question.\u201d<\/p>\n \t\t\t\t\t\t\tSalsa reentered Earth\u2019s atmosphere and was captured as a small, bright dot. Credit: ESA\/ROSIE\/University of Southern Queensland. Acknowledgement: Image taken by Ranjith Ravichandran and Gerard Armstrong.<\/a><\/p>\n \u201cAnother surprise came from the spacecraft themselves. During their penultimate perigee passage before reentry, the satellites remained fully intact and healthy even as they descended to an altitude of about 110 km while travelling at more than 10 km\/s\u2014making them the lowest-flying active spacecraft ever,\u201d says Bruno Sousa, Cluster Spacecraft Operations Manager at ESA.<\/p>\n \u201cUnfortunately, the higher temperatures experienced by the solar arrays caused a severe power shortage and eventually triggered a reboot. As a result, the recorded data could not be preserved and retrieved, preventing us from reconstructing what the spacecraft experienced at that altitude. Nevertheless, we were able to resume normal control afterwards.\u201d<\/p>\n \u201cBecause Samba and Tango are now in a slightly better power state than the first two spacecraft that reentered, they offer a strong opportunity to collect even more complementary data\u2014provided they avoid rebooting this time.\u201d<\/p>\n \tSupporting a sustainable future in space<\/p>\n \t\t\t\t\t\t\tESA’s Draco mission: inside a fiery reentry<\/a><\/p>\n The work to collect the unique reentry dataset for the scientific and engineering community directly supports ESA’s Zero Debris approach<\/a>, which aims to ensure the sustainable use of space for future generations. As more satellites are launched and more missions reach the end of their lives, understanding exactly how spacecraft behave during reentry becomes increasingly important.<\/p>\n That\u2019s why after Samba and Tango\u2019s reentries, there will be Draco\u2019s, ESA\u2019s reentry mission currently being built. Draco<\/a> will record its own fiery demise from the inside as it is observed by scientists on a plane, eager to continue the journey they started with the Cluster quartet.<\/p>\n \u00a0<\/p>\n