Swarm is a European Space Agency (ESA) mission to study the Earth's magnetic field.

The Swarm concept consists of a constellation of three satellite

Satellite

In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....

s in three different polar orbit

Polar orbit

A polar orbit is an orbit in which a satellite passes above or nearly above both poles of the body being orbited on each revolution. It therefore has an inclination of 90 degrees to the equator...

s between 450 and 550 km altitude. The launch will be before mid-2012, in 2010 ESA awarded the contract to Eurockot.

Payload

The payload of the three probes consists of the following instruments:

• Vector Field Magnetometer (VFM): Linear and low-noise measurements of the Earth's magnetic field
  Earth's magnetic field
  Earth's magnetic field is the magnetic field that extends from the Earth's inner core to where it meets the solar wind, a stream of energetic particles emanating from the Sun...
  
   vector components. The fluxgate vector magnetometer is similar to the ones in the satellites Ørsted, CHAMP
  CHAMP
  CHAllenging Minisatellite Payload is a German satellite launched July 15, 2000 from Plesetsk, Russia and was used for atmospheric and ionospheric research, as well as other geoscientific applications, such as GPS radio occultation....
  
   and SAC-C.
• Absolute Scalar Magnetometer (ASM): Calibration of the main instrument VFM.
• Electric Field Instrument (EFI): Measurement of ion density, drift velocity and electric field
  Electric field
  In physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...
  
  .
• Accelerometer (ACC): Measurement of non-gravitational accelerations like air-drag, winds, Earth albedo
  Albedo
  Albedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it...
  
   and solar radiation pressure
  Radiation pressure
  Radiation pressure is the pressure exerted upon any surface exposed to electromagnetic radiation. If absorbed, the pressure is the power flux density divided by the speed of light...
  
  .
• Laser Range Reflector (LRR): Reflecting quartz
  Quartz
  Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
  
   prism
  Prism (optics)
  In optics, a prism is a transparent optical element with flat, polished surfaces that refract light. The exact angles between the surfaces depend on the application. The traditional geometrical shape is that of a triangular prism with a triangular base and rectangular sides, and in colloquial use...
  
  s as part of the satellite laser ranging
  Satellite laser ranging
  In satellite laser ranging a global network of observation stations measure the round trip time of flight of ultrashort pulses of light to satellites equipped with retroreflectors...
  
  network.

External links

• ESA web page on the mission