The Swarm mission will provide the best-ever survey of the Earth's geomagnetic field and its temporal evolution, in order to gain new insights into the Earth system by improving our understanding of our planet's interior and physical climate.

Swarm will consist of a constellation of three satellites orbiting in two different near-polar orbits at 450 and 530 km altitude. The primary ground station will be Kiruna, while the mission's Processing and Archiving Element, managed by ESA/ESRIN, will oversee the generation of products from the science data stream and interface with users.

The mission

The Swarm Mission Operations Centre (MOC) is being established at ESOC, Darmstadt, Germany.

ROLE	Earth observation (EO)
LAUNCH DATE	Second-half 2012
LAUNCHER/LOCATION	Rockot, Plesetsk Cosmodrome
LAUNCH MASS	500 kg each satellite (two configurations)
ORBIT	Near-polar, two satellites at 450 km; one at 530 km
PERIOD	15 orbits daily
NOMINAL MISSION	4 years
+ Most accurate survey ever of the Earth's geomagnetic field +

The Flight Control Team

The Flight Control Team will operate from a Dedicated Control Room located at ESOC. Juan Piñeiro, an experienced engineer, is now acting as Spacecraft Operations Manager.

From 2007-11, ESOC engineers and mission planners will develop plans for the overall ground control infrastructure, flight control procedures and interfaces with other teams. Training for the Flight Control Team will begin in earnest about 12 months prior to launch.

Mission operations overview

The three Swarm satellites are expected to be launched together on Rockot launcher.

Once in orbit, all operations will be controlled from ESOC, while data processing and archiving will be handled from ESA/ESRIN. Kiruna is expected to serve as the mission's dedicated ground tracking station, with other stations providing support as needed.

All Swarm satellites will be placed into orbit by a single launch vehicle. After separation from the launcher, the satellites' subsystems will be activated to allow contact between the satellites and ground stations.

In the Launch and Early Orbit Phase (LEOP) at least three ground stations will be involved. LEOP is expected to last 3 days for the full activation of the satellites, followed by an orbit acquisition phase of up to three months. In parallel with the orbit acquisition phase, the commissioning phase will start in order to check out all satellite subsystems and the payload. The commissioning phase is currently expected to last three months.

After the commissioning phase the nominal mission phase of 4 year starts.

In routine operations, the Flight Control Team will manage:

• Overall satellite operations planning
• Satellite monitoring and control
• Flight dynamics and manoeuvre
• On-board software maintenance
• Mission simulation

The ground station - Kiruna

For routine operations, the mission plans to use the Kiruna ground station – part of ESA's ESTRACK global network –for command, control and tracking of the three satellites.

Kiruna is expected to provide daily visibility for the satellites in both the upper and lower Swarm orbits; ; the number of visible passes per day will vary from 9 for the upper satellite at beginning of mission, to 6 for the lower pair at the end of mission, when the orbit altitude will be as low as 300 km. For routine operations it is expected that one pass per day per satellite will be sufficient to cover the monitoring and control needs.

TT&C (Tracking, Telemetry & Commanding) communication will be done at S-band frequencies, providing an uplink of 4 kbps and a downlink of 6 Mbps.

Ground segment & mission control system

Swarm is expected to use the SCOS-2000 Mission Control System software developed at ESOC.

The platform and payload

The platform

The Swarm platform - the portion of the spacecraft dedicated to flight operations - comprises the following subsystems:

• Structure/mechanical
• Power
• Telemetry/telecommand
• Attitude and orbit control (AOC)
• Thermal control
• Data handling

The overall structure consists of the Bus Assembly, Solar Generator Assembly, Boom Assembly and Launch Adaptor.

The requirements for gathering the mission's magnetic data are very stringent, and this imposes the need to optimise and control the magnetic properties of the spacecraft's physical structure. An important design measure is the accommodation of the magnetometer package at a distance from the main body/platform sufficient to minimise any magnetic disturbance.

A boom ensures a magnetically 'clean' environment and provides very stable accommodation for the magnetometer package. Due to envelope constraints of the launcher fairing, the boom must be deployable.

The payload

Each satellite will carry a science payload consisting of the following instruments:

• Absolute Scalar Magnetometer (ASM)
• Vector Field Magnetometer (VFM)
• Electrical Field Instrument (EFI)
• Accelerometer (ACC)
• Laser Retro Reflector (LRR)