Swarm is ESA's first constellation mission for Earth Observation (EO). The mission consists of three identical satellites named Alpha, Bravo, and Charlie; launched on 22 November 2013 into a near-polar orbit.
Swarm is dedicated to creating a highly detailed survey of the 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 final 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 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.
In March 2018, the CASSIOPE/ e-POP mission was formally integrated into the Swarm constellation as the fourth element (Swarm-Echo) 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.