Cluster mission ends with controlled re-entry of the satellite Salsa-C2

2023-2024
After more than 24 years in orbit, the Cluster mission is coming to an end. On Sunday 8 September 2024, a first satellite of this ESA mission, Salsa-C2, re-entered the Earth's atmosphere over the South Pacific Ocean, ending a very long space adventure.

Launched in 2000, the four identical satellites of the Cluster mission have been studying the interaction between the solar wind and the magnetic bubble surrounding the Earth, the magnetosphere.

The Cluster mission

The four identical Cluster satellites collected unique data on the Earth's magnetosphere and the near-Earth solar wind using 11 scientific instruments over a period of more than 24 years. 

This unique configuration has enabled us to make precise measurements of magnetic field fluctuations, to analyse the electromagnetic waves and to detect the density, temperature and velocity variations of the ionized gas (a plasma consisting of ions and electrons) present in the different sub-regions of the magnetosphere. But every scientific mission comes to an end...  

The beginning of the end

On 8 September 2024, a first satellite of the mission (C2-Salsa) has re-entered the Earth's atmosphere, followed by the three others over the next few years (C1-Rumba in November 2025, C3-Samba and C4-Tango in August 2026). 

After the end of the measurements in September 2024, the three remaining satellites have been put on standby and then ESA operators continue to monitor them to minimize the risk of collision with other satellites and to avoid re-entry over inhabited areas of the Earth.

BIRA-IASB's involvement in the Cluster mission

BIRA-IASB has been involved in the Cluster mission since its conception, in collaboration with ESA and other European and American scientific institutions. BIRA-IASB researchers contributed to the development of the instrument WHISPER (Waves of HIgh frequency and Sounder for Probing of Electron density by Relaxation), which was carried by each of the four Cluster satellites. 

This instrument not only measured the electromagnetic waves propagating in the magnetosphere, but also provided very precise values of electron density. BIRA-IASB has also been heavily involved in analysing data from another wave measurement instrument, STAFF (Spatio-Temporal Analysis of Field Fluctuation). 

As Cluster was the first mission with 4 spacecraft, BIRA-IASB scientists have invented new techniques to interpret the measurements made simultaneously by the four closely spaced satellites. They have published numerous studies that exploit Cluster measurements, thereby contributing to improving the knowledge of our space environment, from the upper atmosphere where polar auroras form to the outer regions of the magnetosphere where it interacts with the solar wind. 

Examples include the edition of a book on the plasmasphere largely based on Cluster data, the creation of a video about the plasmasphere and the edition of a book on the magnetosphere. 

Over the last two years, BIRA-IASB has also been involved in the GRMB (Geospace Region and Magnetospheric Boundary) project, a global analysis of data from the entire Cluster mission.
 

More:

 

Infographic describing how Salsa-C2 has re-entered Earth’s atmosphere
Salsa-C2 re-entered Earth’s atmosphere. (Credit: ESA).
Infographic describing how Salsa-C2 has re-entered Earth’s atmosphere
Infographic describing how a first of four Cluster satellites, Salsa-C2, has re-entered the Earth’s atmosphere over the South Pacific Ocean, on 8 September 2024 (Credit: ESA).
Earth's surface at the bottom and a bright spot (Salsa-C2 satellite)
Black and white image taken from an aircraft showing the Earth's surface at the bottom and a bright spot above the Earth's surface. This dot corresponds to the Salsa-C2 satellite, which has re-entered the Earth's atmosphere on 8 September 2024 in the South Pacific Ocean, west of Chile. (Credits: ESA/ROSIE/University of Southern Queensland. Photo taken by Ranjith Ravichandran and Gerard Armstrong)