Hera is ESA's first planetary defence mission, set to probe the lingering mysteries of a unique target among the 1.3 million known asteroids of our Solar System: the first body to have had its orbit shifted by human action.

Spacecraft are among the most complex machines ever built, so need to be broken down into sets of subsystems, and this video shows how ESA and European industry put together Hera.

Hera’s chemical propulsion subsystem is what moves it through space, while its electrical power subsystem supplies and regulates electrical power throughout the spacecraft as needed. Its data handling subsystem sends commands and stores data while its electrical harness is all the wiring needed to interlink its component elements.

The spacecraft structural subsystem forms its ‘body’: a central carbon fibre reinforced polymer body can be thought of as Hera’s backbone, from which aluminium honeycomb panels are attached. Upon these panels are hosted the communication subsystem that allows Hera to transmit and receive signals to and from Earth – supplemented by the inter-satellite links used to communicate with its two CubeSats once deployed – as well as Hera’s guidance, navigation and control equipment.

Keeping the spacecraft supplied with electrical power are its twin 5-m long solar arrays flanking Hera. Atop its cube-shaped body on the mission’s ‘Asteroid Deck’ are hosted the Deep Space Deployers that will eject the Juventas and Milani CubeSats in the vicinity of its target asteroid, near its redundant Asteroid Framing Cameras and other key instruments: its Thermal Infrared Imager for nightside asteroid observations and its PALT laser rangefinder to measure Hera’s distance from the asteroid’s surface.

HyperScout H is a hyperspectral imager to prospect the asteroid, while the Spacecraft Monitoring Camera will survey the Asteroid Deck itself, which will be especially useful to track the CubeSat deployments. Supplementary scientific data will be gathered via a radio science experiment as part of the communication subsystem.

In the last phase of its mission Hera will perform an autonomous navigation experiment guided by visual imaging of asteroid surface features, made possible by a dedicated image processing unit. Then comes the thermal control subsystem to maintain Hera at a benign operating temperature amid the extreme conditions of space: this includes multi-layer insulation, which gives spacecraft their distinct ‘Christmas wrapping’ appearance plus radiators beside its solar arrays, which are used to radiate unwanted heat into cold space.