The Swarm mission is a European Space Agency (ESA) project that was proposed in early 2002 by scientists from institutions across Europe and the USA. The goal of Swarm is to study and precisely measure Earth’s magnetic field and its temporal variations, in order to gain new insights into our planet’s interior and climate.
The Swarm concept consists of a constellation of three identical satellites flying in coordinated polar orbits between 450-530 km altitude. Two satellites, Swarm A and Swarm C, orbit side-by-side at lower altitude collecting data simultaneously, while the third satellite, Swarm B, flies at higher altitude. The slight difference in inclination between the upper and lower satellite pairs causes their orbital planes to drift relative to one another, allowing the constellation to sample the entire Earth over time.
Each Swarm satellite carries precision magnetometers and other specialized instruments to measure the strength, direction, and variations of the magnetic field with high accuracy. Additional sensors record electric field, plasma density, temperature, and spacecraft positions. The coordinated swarm concept, with simultaneous multipoint measurements, provides unprecedented resolution to distinguish between the various sources that contribute to Earth’s complex magnetic field.
The key sources measured by Swarm include the core field originating from the planet’s interior; the lithospheric field from magnetized crustal rocks; fields induced by the solar wind interaction with Earth’s ionosphere and magnetosphere; and fields induced in the oceans and atmosphere. Together, these components give insight into the geomagnetic dynamo process linked to motion of liquid iron alloys in Earth’s outer core over 3000 km below the surface.
In addition to improving models of Earth’s interior and core dynamics, Swarm data enhances understanding of space weather conditions in the magnetosphere and ionosphere that can affect satellites, communication systems, power grids, and GPS signals. The constellation also provides independent data on ocean circulation patterns and conductivity structures deep beneath the seabed.
ESA manages the Swarm mission with funding support from national agencies in European countries and the USA. The satellites were built by European aerospace company Airbus Defence and Space Germany, with specialized instruments contributed by research institutes in France, Denmark, Canada, and Austria. They were launched together on a Russian Rockot vehicle from Plesetsk Cosmodrome in November 2013.
During the initial 3-month commissioning phase, the trio of Swarm satellites were maneuvered into their finely tuned science orbits. Two lower satellites orbit at 460 km altitude in near identical orbits, flying only 1.4 degrees apart in longitude. The higher satellite reaches an initial altitude of 530 km in a slightly different inclination. Ground teams monitor the satellites daily and perform maneuvers every few months to maintain precise positioning throughout the multi-year mission.
The Swarm orbit and instrument design was optimized based on experience and data from preceding magnetic field missions like Ørsted, CHAMP, and SAC-C. However, Swarm’s unique constellation concept provides the first ever magnetic survey with simultaneous measurements from different locations in space. This multi-point perspective facilitates separation of the various magnetic signals from core, crust, oceans, ionosphere that overlap at single points of observation.
As part of the Swarm data processing system, ESA makes available a highly interactive online data manipulation and visualization tool for Swarm products called VirES. Level 1b raw instrument data and Level 2 processed models and images are freely available from this interface or by FTP download to registered users.
In the UK, Swarm data processing and distribution activities are conducted by a consortium of research facilities with magnetic field expertise, including the British Geological Survey (BGS) and several universities. The various Swarm data products they generate help researchers isolate and study specific source signals that contribute to Earth’s complex dynamic magnetic field.
The Swarm satellites and instruments continue to perform well after the 10 year milestone in 2023. Based on positive assessments by ESA’s Earth Advisory Committee for the quality and relevance of Swarm’s data, the mission has been approved for extensions up to 2025, nearly doubling the originally planned lifetime. Scientists anticipate a wealth of new discoveries about Earth’s interior makeup and processes as the unique Swarm constellation mission continues collecting valuable magnetic field measurements from space.
Reference: EO Portal