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About Swarm

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Swarm is ESA's first constellation mission for Earth Observation (EO). The mission consists of three identical satellites named Alpha, Bravo, and Charlie (A, B and C); which were launched on 22 November 2013 into a near-polar orbit.

Swarm is dedicated to creating a highly detailed survey of Earth's geomagnetic field and its temporal evolution as well as the electric field in the atmosphere, by using a satellite constellation that carries sophisticated magnetometers and other instruments.

The initial constellation of the mission was achieved on 17 April 2014. Swarm A and C form the lower pair of satellites flying side-by-side (1.4° separation in longitude at the equator) at an altitude of 462 km (initial altitude) and at 87.35° inclination angle, whereas Swarm B is cruising at a higher orbit of 511 km (initial altitude) and at 87.75° inclination angle. Due to the subtle difference in altitude and inclination, the Swarm B orbit drifts slowly away from the Swarm A/C orbits at a rate of about 24°/year (difference in longitude of the ascending node). In October 2021, the orbital planes realigned, Swarm B counter-rotating with respect to Swarm A and C. To maximise the scientific return of this conjunction, the Swarm A and C satellites were brought back into the same orbital plane, starting with a manoeuvre in October 2019 that would slowly reduce the separation in longitude, achieving a perfect alignment at the exact time of the conjunction with Swarm B. During the conjunction, the distance between the Swarm A and C satellites was reduced to only 2 s along the orbit (15 km), which was previously kept between 4–10 s for safety reasons.

In March 2018, the CASSIOPE/e-POP mission was formally integrated into the Swarm constellation as the fourth element (Swarm-E) under ESA's Earthnet Third Party Mission Programme. The e-POP payload operations are currently focused on maximising the Swarm/e-POP scientific outcome, and there is an ongoing joint effort to develop new and better-calibrated products based on e-POP data.

Swarm was designed to operate for four years, following a three-month commissioning phase. In November 2017, the mission was granted a four-year extension to 2021. It was then extended further and will operate till 2025.

Swarm Objectives

Earths Magnetic Core

The Swarm mission primary objectives are:

  • Study of core dynamics, geodynamo processes and core-mantle interaction
  • Mapping of lithospheric magnetisation and its geological interpretation
  • Determination of the 3D electrical conductivity of the mantle
  • Investigatigation of electric currents flowing in the magnetosphere and ionosphere.

The secondary objectives are:

  • Identifying the ocean circulation by its magnetic signature
  • Quantifying the magnetic forcing of the upper atmosphere.

Swarm Instruments

Swarm instruments

The Absolute Scalar Magnetometer (ASM) measures the strength of the magnetic field also used to a great accuracy. It provides scalar measurements of the magnetic field to calibrate the onboard Vector Field Magnetometer. The ASM is an absolute instrument, i.e. it is not subject to changes of its intrinsic parameters over time.
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The Electrical Field Instrument consists of two components: the Langmuir Probe (LP) and the Thermal Ion Imager (TII). The probes provide measurements of the electron density, electron temperature and spacecraft potential. The TII characterises the ion drift and velocity in high resolution to determine the electric field around Earth.
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The Vector Field Magnetometer is Swarm’s core instrument. It makes high-precision measurements of the magnitude and direction of the magnetic field, i.e. the field’s vector. The orientation of the vector is determined by the star tracker assembly, which provides attitude data.

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The Star Tracker is comprised of three Camera Head Units (CHUs) mounted on the innermost end of the optical bench. It retrieves information on the precise satellite orientation and attitude in space.

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The GPS Receiver receives signals from any GPS satellites visible to its antenna. The GPSR provides an accurate location and time reference to the main instruments on board the Swarm satellites. The Laser Retro-Reflector is used for external calibration and validation of the on board GPS receiver. This instrument provides positioning information through ground-based satellite laser ranging. find out more
The Accelerometer measures the satellite’s non-gravitational acceleration in its respective orbit. The instrument helps scientists to study factors that cause non-gravitational accelerations such as air drag, winds, Earth albedo, and direct solar radiation pressure on the spacecraft.

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