FMPI scientists on a unique satellite hunt over the Pacific
Slovak scientists from Comenius University Bratislava have once again made history in space safety research. They took part in ROSIE, an international airborne expedition supported by the European Space Agency (ESA), to document the controlled re-entry and break-up of two satellites at close range over the South Pacific.
ESA’s Cluster-II mission spent many years studying the space environment. When the mission came to an end, specialists planned the satellites’ controlled re-entry into the atmosphere, where they would burn up safely. Following successful observations of the first satellite, Salsa, in 2024, scientists turned their attention to the final pair, Samba and Tango, in late August and early September 2026.
A flying laboratory aboard a jet
The ROSIE mission (Re-entry Observation Setup and International Execution) aimed to collect the most precise astrometric, photometric and spectroscopic data possible on how objects break apart as they enter the Earth’s atmosphere. Capturing these hard-to-obtain measurements required meticulous planning and extensive logistical and technical preparation:
· Preparations in Sydney: The scientific team assembled in Sydney, Australia, on 24 August 2026, where they transformed a private jet operated by Falcon Air into a flying laboratory equipped with 60 specialised instruments.
· Transfer to Tonga: The team then travelled from Australia to the islands of Tonga, the closest inhabited land to the predicted re-entry area.
· Successful observations from 150 km away: Although adverse weather prevented observations from the ground or from ships, precise calculations and flight planning enabled the airborne team to record the break-up of Samba on 31 August and the final satellite, Tango, on 1 September, from a distance of approximately 150 km.
Slovakia’s key role in the ESA project
Slovak experts played a prominent role in the international mission. Astros Solutions s.r.o. managed and coordinated ROSIE on ESA’s behalf. The company is led by Dr Jiří Šilha and Dr Matej Zigo, both graduates of the Faculty of Mathematics, Physics and Informatics at Comenius University Bratislava (FMPI CU).
Tomáš Vörös, MSc, and Dr Tomáš Paulech joined the observation flights over the Pacific on behalf of FMPI CU. Both work in the Division of Astronomy and Astrophysics within the Department of Astronomy, Physics of the Earth and Meteorology.
Why were close-range observations so important?
Visible-light and infrared recordings of the satellites breaking apart provide unique insights into how materials fragment in the atmosphere. As the number of satellites in orbit grows rapidly, ensuring space safety and reducing space debris are becoming ever more pressing priorities.
The European Space Agency also highlighted the success of ROSIE. The mission’s success demonstrates that CU researchers and graduates are among the world’s leading space scientists.
Photo 1: The ROSIE team fits instruments aboard the aircraft ahead of the campaign to observe the re-entry of the Cluster satellites Samba and Tango. Preparations took place in Bankstown, Australia, in late August 2026. Led by Astros Solutions, the team aimed to gather as much re-entry data as possible as Cluster 3 and 4 entered the Earth’s atmosphere. The satellites re-entered approximately 24 hours apart over a remote area of the South Pacific, on 31 August and 1 September 2026 respectively. Credit: Astros Solutions/ROSIE.
Photo 2: On 31 August and 1 September 2026, the last two of the four satellites that made up ESA’s Cluster mission entered the Earth’s atmosphere over a remote area of the South Pacific. The two satellites, Samba and Tango, followed similar trajectories about 24 hours apart. The ground station at Kourou in French Guiana (KRU) was the last to track the satellites, following them until shortly before they re-entered the atmosphere and burned up. The station’s coverage area is shown in green. Credit: ESA.
Photo 3: Preparing instruments aboard the aircraft. In the foreground are T. Vörös, M. Zigo and J. Šilha. Credit: T. Paulech.