ESA Begins Testing Its First Satellite Constellation

by | Nov 1, 2011

A constellation of three satellites form the Swarm Earth Explorer mission, which will identify and measure Earth's magnetic signals”all of which create the magnetic field that protects our planet.

Marking an important milestone, the first European Space Agency (ESA) Swarm satellite has undergone magnetic testing. Comprising three identical satellites, Swarm isESA's first constellation of Earth observation satellites. They are due to liftoff together from Plesetsk in northern Russia next year to study Earth's magnetic shield.

The magnetic field acts like a shield protecting the planet from charged particles that stream toward Earth in solar winds. Without it, life on Earth could not exist.


It is known that the field is mainly generated deep inside Earth by an ocean of swirling iron that makes up the liquid outer core. Other sources of magnetism come from rocks in the crust and electric currents flowing in the ionosphere, magnetosphere and oceans.

However, Earth's magnetic field holds many mysteries; how it is generated and how it changes over time is complex and not fully understood. It is in a constant state of flux and, currently, shows signs of weakening.

ESA's Earth Explorer Swarm mission sets out to improve our understanding of this enigmatic force. This information will provide insight into processes occurring deep inside the planet and yield a better understanding of the near-Earth electromagnetic environment and the impact solar wind has on Earth.


To do this, the satellites carry a new generation of magnetometers to identify and measure the magnetic signals that stem from the various sources with unprecedented accuracy. These advanced sensors are mounted on the satellite's 4-meter-long boom to minimize interference from the electric units on the craft.

Carried out by engineers from EADS-Astrium, the testing program began over a year ago. This long series of tests simulates the harsh environment of space, exposing each satellite to different temperatures, vibration and shocks. So far, all the instruments and satellites have performed well.

As part of this intense period, the first of the three satellites recently completed the all-important magnetic tests. The satellites and instruments are, in themselves, magnetic and therefore influence the measurements they make. The origins of all the magnetic signals stemming from different parts of the satellites have to be determined and accounted for carefully so the measurements taken in orbit are not misinterpreted.

These particular tests are carried out in a magnetically clean environment“hence a wooden floor, which may seem a little unusual for a satellite cleanroom. In fact, the magnetic testing facility is in a forest, far from any other buildings to minimize any magnetic disturbance.

Determining the magnetic properties of the satellite and different instruments is a painstaking exercise. The satellite is put in a number of positions and readings are taken to work out where the signals come from and how strong they are.

One of the most important tests is to characterize the properties of the magnetotorquers, which are used continuously to keep the satellites at the correct attitude as they orbit Earth. As their name suggests, they are magnetic, so an accurate assessment of the field they generate is essential to the mission's accuracy.

The testing program will conclude next February, after which the three satellites will be packed up and shipped to the Plesetsk Cosmodrome where they will be made ready for launch in July 2012.

Image Courtesy ofESA/P. Carril

Source: Red Orbit


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