Swarm (spacecraft)

The overall objective of the Swarm mission is to build on the experience from the Ørsted and CHAMP missions and to provide the best ever survey of the geomagnetic field (multi-point measurements) and its temporal evolution, to gain new insights into the Earth system by improving our understanding of the Earth's interior and climate.[1]

The Swarm constellation consists of three satellites (Alpha, Bravo and Charlie) placed in two different polar orbits, two flying side by side at an altitude of 450 kilometres (280 mi) and a third at an altitude of 530 kilometres (330 mi).[1][2] The launch was delayed and rescheduled to 12:02:29 UTC on 22 November 2013, from Plesetsk Cosmodrome, Russia.[3] ESA contracted Astrium to develop and build the three orbiters,[1] while Eurockot provided the launch services.[4]

Through a Canadian-European partnership, the Canadian Space Agency's CASSIOPE satellite's e-POP instrument suite was formally integrated as the fourth satellite in the Swarm constellation in 2018, joining Alpha, Bravo, and Charlie as Echo.[5]

Primary objectives:

• Earth core dynamics, geodynamo processes, and core-mantle interaction
• Lithospheric magnetization and its geological interpretation
• 3D electrical conductivity of the mantle
• Currents flowing in the magnetosphere and ionosphere

Secondary objectives:

• Identification of the ocean circulation by its magnetic signature
• Quantification of the magnetic forcing of the upper atmosphere

The payload of the three spacecraft consists of the following instruments:[2]

• Vector Field Magnetometer (VFM): Linear and low-noise measurements of the Earth's magnetic field vector components. The fluxgate vector magnetometer is similar to the ones in the satellites Ørsted, CHAMP and SAC-C.
• Absolute Scalar Magnetometer (ASM): its main goal is the calibration of the main instrument VFM. It consist in a scalar optically pumped magnetometer based on metastable helium-4 designed by CEA-Leti.[6]
• Electric Field Instrument (EFI): Measurement of ion density, drift velocity and electric field.
• Accelerometer (ACC): Measurement of non-gravitational accelerations like air-drag, winds, Earth albedo and solar radiation pressure.
• Laser Range Reflector (LRR): Reflecting quartz prisms as part of the satellite laser ranging network.

In September 2016, scientists published a study that revealed a direct link between GPS blackouts of low-Earth-orbiting satellites and "thunderstorms" in the ionosphere. During the first two years of Swarm's operation their GPS connection was broken 166 times.[10] The high-resolution observations from the satellite helped to link these outages to ionospheric thunderstorms at altitudes of 300–600 km in the Earth's atmosphere.[11]

In December 2016, scientists announced that, by using data from the Swarm satellites, they had discovered a new feature in the Earth's outer core, a jet-stream of rapidly moving liquid iron moving at around 50 km per year.[12][13]

In April 2017, Swarm's data was used to confirm that Steve was a previously unrecognized atmospheric phenomenon.[14]

In May 2020, Swarm revealed that Earth's magnetic field is gradually weakening in an area stretching from Africa to South America, which might cause technical disturbances in satellites orbiting Earth.[15]

• ESA's Living Planet Programme
  • GOCE
  • SMOS
  • CryoSat and CryoSat-2
  • ADM-Aeolus
  • EarthCARE
  • BIOMASS
  • FLEX
• Magsat
• Ørsted (satellite)
• Cluster (mission)
• CHAMP (satellite)

• ESA web page on the mission
• eoPortal page of Swarm