Harmony A, B (Earth Explorer 10)

Harmony [DLR]

ESA’s Earth Observation Programme Board has selected Harmony (formerly known as Stereoid, Stereo Thermo-optically Enhanced Radar for Earth, Ocean, Ice, and land Dynamics) to become the tenth Earth Explorer mission. Harmony will comprise two identical satellites orbiting Earth in convoy with a Copernicus Sentinel-1 satellite. Each Harmony satellite will carry a receive-only C-band synthetic aperture radar and a multiview thermal-infrared instrument.

Harmony’s mission concept is to fly two C-band receive-only radar satellites in a configurable formation with Sentinel-1 C or D, which will be used as illuminator. Formation flying allows an in-orbit reconfiguration of the observation geometry. This in-orbit configurability is the key enabling the multi-purpose nature of the mission. In addition the payload will include a compact TIR camera.

Working with Sentinel-1, the two Harmony’s would provide data to measure small shifts in the shape of the land surface and of glaciers. They would also carry a multibeam thermal-infrared instrument to measure cloud movements and the sea-surface and would provide simultaneous measurements of wind, waves, and currents. Technically, Harmony enables unique measurements over timescales ranging from tens of milliseconds (to measure ocean currents) to years (to measure solid Earth surface motion).

Harmony will alternate between two flying configurations:

• A close-formation configuration focused on single-pass cross-track interferometric measurements.
• A so-called stereo configuration, during which one of two spacecraft, Harmony-A (Concordia), will fly in the order of 300 km ahead of Sentinel-1, while the other, Harmony-B (Discordia), will fly roughly at about the same distance behind Sentinel-1. This maximizes the line-of-sight (LoS) diversity, hereby providing the best sensitivity to motion-vectors.

Launch is planned for 2029 on a Vega-C.