ESA’s Cluster mission draws to a close

Cluster is the world’s first space mission consisting of four identical satellites. Its aim was to resolve the time-space ambiguity and measure the Earth’s plasma environment in three dimensions, right into the solar wind.

Its instruments are highly sensitive :

• the STAFF instrument, jointly developed by DESPA (now the Laboratoire d’études spatiales et d’instrumentation en astrophysique - LESIA at Paris Observatory - PSL) and CETP (now the Laboratoire de physique des plasmas - LPP at Ecole Polytechnique), remains the world’s most sensitive instrument for resolving the end of the electromagnetic turbulence cascade on scales shorter than a kilometer !

As a reminder, the Earth’s magnetosphere encompasses a region with a radius of almost 100,000 kilometers around the Earth.

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Read also the information [in English]
on the ESA website :
"Frequently asked questions : Cluster’s Salsa reentry"

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On September 8, 2024 at 20:02 CEST, the Salsa satellite (the second of Cluster’s four satellites) will re-enter the Earth’s atmosphere, before reaching an uninhabited area in the southern Pacific Ocean.

Cluster 1 (Rumba) will re-enter in autumn 2025, followed by the last two satellites, Samba and Tango, in summer 2026.

Scientific operations will end on September 30, 2024.

An Enduring Mission

Did you know ? This mission was originally the (free) payload of the very first Ariane 5, which exploded on lift-off on June 4, 1996. However, the military recovered one of the analyzers - STAFF-SA - built at the Paris Observatory on its Meudon campus, from the Guiana mangroves, and which, after cleaning, was still functional (it is on display in a showcase in the Jean-Louis Steinberg building in Meudon). A memorable consolation drink was organized at the laboratory, where the instrument took pride of place amidst a large platter of seafood... The second version, launched by two successive Soyuzes in 2000, was the source of an abundant scientific harvest : in total, this mission will have given rise to over 3,600 published scientific articles.

After 24 years in space, since the launches of July and August 2000, Cluster will have operated well beyond its initially scheduled 2-year lifespan.

Many operational challenges have been met, including :

• crossing thousands of eclipses without any batteries ;
• recovering a satellite after losing telemetry for three days ;
• and the recovery of an instrument following a computer hack ;

Cluster’s most important results for Observatoire de Paris-PSL are :

• The charactera0on of shock motion upstream of the Earth’s magnetosphere, as if the magnetosphere were breathing [1] ;
• The discovery of magne0c vortices downstream of the terrestrial shock, then in the solar wind.
  Today, the signatures of these vortices (known as "Alfven vortices") are found closer to the Sun
  with Parker Solar Probe [2] ;
• The first statistical study of "Whistler" waves in the solar wind (this publication [3] is now the reference for all Solar Orbiter and Parker Solar Probe studies of these waves).
  https://en.wikipedia.org/wiki/Cluster_II_(spacecrab)).

These results continue to inspire researchers at Paris Observatory (and worldwide en0er) today, and have opened up new ques0ons to be solved with the ongoing Parker Solar Probe (NASA) and Solar Orbiter (ESA/Nasa) missions.

Fun fact : originally, this mission was the (free) payload of the very first Ariane 5, which exploded at lift-off on June 4, 1996. Nevertheless, the military salvaged one of the STAFF-SA analyzers built in Meudon from the Guiana mangrove swamp, which, after cleaning, was still functional (it is on display in a showcase in the Jean-Louis Steinberg building on the Meudon campus of the Observatoire de Paris-PSL). A memorable pot de consola0on was organized at the laboratory, where the instrument took pride of place amidst a large seafood platter... The second version, launched by two successive Soyuzes in 2000, was the source of an abundant scientific harvest for LESIA researchers at Paris-PSL Observatory.

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