The FLEX mission consists of a single three-axis stabilised satellite flying in tandem with Copernicus Sentinel-3 to make optimal use of existing relevant space observation capabilities, providing a suite of complementary measurements acquired within 6 - 15 seconds of each other in order to minimise the effects of moving clouds. It is expected that FLEX will orbit 100 km ahead of one of the Sentinel-3 satellites.

The FLEX satellite configuration designs are based on careful consideration of:

• Accommodation of the FLORIS payload so the instrument has an unobstructed view of the Earth
• Pointing and co-registration requirements, which favour the isostatic mounting of the instrument on a specific payload support panel
• Line of sight stability
• Vega launcher fairing envelope, limiting the size and shape of the instrument and overall satellite

The FLEX satellite will be 1.5 x 1.2 x 1.2 m in size, and when in orbit will deploy two solar array panels, resulting in a total width of 5.2 m. The satellite will have a mass of approximately 460 kg (including 140 kg instrument and 30 kg propellant).

FLEX will operate in a Sun-synchronous orbit at an altitude of 814 km, with an inclination of 98.64° and a 27-day repeat cycle.

A series of ground facilities will support the mission:

• Mission control: ESA's European Space Operations Centre (ESOC) in Darmstadt, Germany. Additionally, the tandem operations with Copernicus Sentinel-3 will be coordinated with EUMETSAT
• Communication links: X-band science data via Svalbard and Norway, and S-band telemetry via Kiruna in Sweden
• Data: ESA's Centre for Earth Observation (ESRIN) in Frascati, Italy

Learn about ESA's upcoming FLEX mission in this infographic: