Benefiting from the technological excellence Europe and Canada have to offer, the Swarm satellites carry a comprehensive range of new-generation instruments to deliver extremely accurate data to advance our understanding of Earth’s magnetic field.

Vector Field Magnetometer
This magnetometer is the mission’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 startracker assembly, which provides attitude data. The vector field magnetometer and the startrackers are both housed on an ultra-stable structure called an optical bench, halfway along the satellite’s boom. The design of the bench and carefully selected material make it possible to keep the instruments aligned to 1 arcsec.

Achieving this level of stability posed a particular design challenge, because the instruments have to withstand huge swings of temperature as the satellite passes in and out of sunlight. This latest generation of instruments was developed and manufactured at the Technical University of Denmark.

Absolute Scalar Magnetometer
This novel instrument measures the strength of the magnetic field to greater accuracy than any other magnetometer. The absolute scalar magnetometer is an ‘optically-pumped metastable helium-4 magnetometer’, developed and manufactured by CEA-Leti in France under contract with the French space agency, CNES. It provides scalar measurements of the magnetic field to calibrate the vector field magnetometer.

Accelerometer
This unit measures the satellite’s non-gravitational acceleration in its respective orbit and, in turn, provides information about air drag and solar wind. Air density models will be derived from these products and will be used with the magnetic data for new insights into how solar wind affects upper-atmosphere dynamics. The instrument was designed and manufactured by the Czech Republic’s Aerospace Research and Test Establishment, VZLU – the first time that ESA has contracted an instrument of this complexity to Czech industry.

Swarm instruments (front view)

Electrical Field Instrument
This instrument, positioned at the front of each satellite, measures plasma density, drift and acceleration in high resolution to characterise the electric field around Earth. Developed by COM DEV in Canada, this instrument is the first 3D ionospheric imager in orbit. It carries an ingenious thermal-ion imager from the University of Calgary (Canada), and the Swedish Institute of Space Physics, IRFU, developed a unique concept for the sensors in the Langmuir probe. This probe provides measurements of electron density, electron temperature and the electric potential of the satellite.

GPS Receiver and Laser Retroreflector
Precise orbit determination relies on the data from the GPS receivers, which were developed by RUAG Space in Austria. Each satellite is equipped with a laser retroreflector from the German GFZ Research Centre for Geosciences to validate the GPS system.