The 4 equivalent satellites of the Cluster II mission studied the interplay of the photo voltaic wind with Earth’s magnetic area. Credit score: ESA – CC BY-SA 3.0 IGO
On July 26, 2000, the European Area Company (ESA) launched the Salsa satellite tv for pc, which joined its three companion satellites — Samba, Rumba, and Tango — on the Cluster II mission, scheduled to final two years. On Sep. 8, after greater than 24 years of service, Salsa re-entered Earth’s environment in a managed de-orbit, the place it broke up over the South Pacific Ocean.
Cluster II was designed to review Earth’s magnetic area, particularly how the photo voltaic wind interacts with it to supply aurorae and geomagnetic storms. The satellites investigated charged particles and magnetic fields throughout huge swaths of the magnetosphere from as shut as 10,000 miles (16,000km) above Earth’s floor out to 120,000 miles (75,000km) — roughly midway to the Moon.
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Cluster II was a near-identical alternative to the unique Cluster mission, which was destroyed in a failed launch in 1996. The equivalent, spinning, drum-shaped satellites of Cluster II flew in a tetrahedral formation and will maneuver steadily, generally bunching as shut as 2.5 miles (4 kilometers), however normally spreading out throughout some 6,200 miles (10,000 km) in area.
Every craft carried a set of devices for measuring the power and density of charged particles and electromagnetic fields and waves, and performing evaluation on the stormy area climate the craft sailed via.
The aim of those devices was to review the small-scale construction of Earth’s plasma atmosphere, particularly the photo voltaic wind-magnetosphere interplay. Specifically, the mission was designed to map and examine the assorted methods wherein Earth’s magnetotail area altered its magnetic area and plasma circumstances through the passage of a coronal mass ejection, a burst of fabric the Solar sometimes flings into area at excessive speeds.
Throughout extreme geomagnetic storms, particle and area circumstances fluctuate quickly in each time and area, which makes in-situ measurements important in understanding this exercise. Cluster II carried out these measurements with aplomb, offering information throughout greater than two full cycles of accelerating and reducing photo voltaic exercise (a photo voltaic cycle is roughly 11 years). Researchers might be mining the information for years to return.
Flying in formation
Cluster II wasn’t the primary or the final mission that consisted of particular person satellites working in a flying constellation. Noteworthy amongst these are the Geostationary Operational Environmental Satellites (GOES), which have been periodically up to date and changed because the first launch in 1975. GOES is accountable for monitoring area climate and Earth’s environment, and has even aided in search and rescue missions.
The 5 satellites of NASA’s Time Historical past of Occasions and Macroscale Interactions throughout Substorms (THEMIS) mission had been launched in 2007 to review magnetic reconnection in Earth’s magnetic area. The NASA mission might fluctuate the separation distance of the maneuverable equivalent satellites to review many alternative scales of the magnetic reconnection phenomenon. Whereas three of the satellites stay in Earth orbit, two now orbit the Moon, to review area climate there.
And naturally many communication satellites fly in formation, from GPS to Starlink, to supply protection throughout Earth’s floor.
A superb life
Cluster II was not designed to be operational without end. A satellite tv for pc like Salsa on the finish of its lifetime can’t be allowed to stay in area to grow to be particles for an additional spacecraft to stumble upon, nor allowed expend within the environment by mere likelihood, its items presumably falling on populated areas. So floor controllers carried out a sequence of maneuvers to ship Salsa right into a managed re-entry Sep. 8.
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Even throughout their final months of operation and atmospheric re-entry, the 4 Cluster II satellites gave scientists a ring-side seat to watch the mysterious area the place charged particles are accelerated earlier than producing the polar aurora. These areas are too excessive for examine by balloon payloads and too low to be studied by spacecraft in secure low Earth orbits.
The remaining spacecraft of the Cluster II constellation might be de-orbited over the following two years, however with Salsa’s re-entry, the mission’s science operations have ended. Over 3,200 analysis papers have been written and printed to this point in regards to the Cluster II science accomplishments, and they’ll absolutely proceed to supply perception for years to return.
