Self-Driving Spacecraft Will Save Earth from Collisions with Asteroids

“While the mission is designed to be fully operated manually from ground, the new technology will be tested once the core mission objectives are achieved and higher risks can be taken.”

Hera’s latest design iteration will be presented to Europe’s space ministers at the Space19+ Ministerial Council this November. 

“The spacecraft will operate like an autonomous vehicle, fusing data from different sensors to build up a coherent model of its surroundings,” says ESA guidance, navigation, and control (GNC) engineer Jesus Gil Fernandez.

“Hera’s most crucial data source will be its Asteroid Framing Camera, combined with inputs from a star-tracker, laser altimeter, thermal infrared camera plus inertial sensors including accelerometers.” 

Being autonomous will allow the Hera to get really close to the surface of the smaller asteroid ‘Didymoon.’

Intimate portraits of asteroid surface

If all goes to plan the spacecraft could get as close as 200 m without fear of being hit by stray debris. Getting so intimate with the moon will allow Hera to take super high-resolution scientific observations down to 2 cm per pixel.

One of the main goals of the mission is to examine the impact crater left by the US DART spacecraft crashing into Didymoon to divert its orbit.

GNC engineer Massimo Casasco adds: “All other deep-space missions, by comparison, have had a definite driver back on Earth, with navigation commands planned at mission control in ESA’s European Space Operations Centre, before being uplinked to the spacecraft hours later. During Hera’s experimental phase, equivalent decisions will be performed aboard on an autonomous basis in real time.”

Jetting off 2023

Hera is planned to launch in October 2023 and will hopefully reach its target about three years later. Currently, Hera will navigate itself using three different modes for different stages of its journey. 

Initially, the main asteroid will appear as one more bright star among many so several photographs will need to be taken to observe its motion against the background starfield.

Once it can locate its target, Hera will go into a mode that it will use for the main part of its journey as it moves from 30 km to 8 km away from the asteroid. At this stage, the larger ‘Didymain’ asteroid will be framed in Hera’s camera view as an overall reference point.

“This mode depends on having the big asteroid smaller than our overall camera field of view, and detecting the contrast of its edges giving way to the space beyond,” says Massimo. 

“We take advantage of its roughly-spherical shape to fit it within a circle and estimate the line-of-sight distance between the spacecraft and the asteroid ‘centroid’."

Once Hera is about 8 km away from the asteroid, it will switch modes again into an autonomous mode where it has absolutely no visual reference. 

Hera’s development as an autonomous spacecraft will open the doors to a more cost-effective vehicle that can move through space without Earth-based input.