Brake! Time for ESA’s Hera asteroid mission to go slow

Launched two years ago today, the European Space Agency’s Hera mission for planetary defence has been hurtling away from Earth ever since. The institutional report frames the development in practical terms and ties it to the broader mission or observing effort.

It matters because Earth science becomes stronger when local observations can be placed inside a broader physical pattern that spans time and geography. The planet operates as a coupled system in which atmospheric, oceanic, cryospheric and solid-Earth processes interact across timescales from days to millions of years. A measurement that captures one variable at one location and one moment has limited interpretive value until it is embedded in the longer series and wider spatial coverage that allow natural variability to be separated from forced change. Hera was launched from Cape Canaveral Space Force Station in Florida, USA on 7 October 2026, just ahead of the incoming Hurricane Milton. Since then Isaac Newton has been doing most of Hera’s driving, punctuated by a pair of deep space manoeuvres plus a crucial spring 2025 flyby of Mars that shifted the spacecraft’s.

Currently flying relative to Earth at a speed of more than 12 kilometres per second, Hera has been moving like a race car changing lanes, first crossing Mars orbit and now closing. Early next Tuesday 15 October Hera will rotate around so that its ring of Orbit Control Thrusters face towards the Didymos system.

Three of these hydrazine-based thrusters will be ignited at once, burning continuously for a total of 93 minutes, to reduce Hera’s velocity relative to the asteroids by a few. As soon as possible after the end of the burn we will acquire a signal from the spacecraft via one of ESA’s two 35-m diameter antenna deep space antennas in New Norcia, Australia.

BRM-2, will be uplinked to Hera to be implemented on the early morning of Thursday 22 October. This second approximately 31 minute thruster burn should complete most of the Delta-V required to match the velocity of the Didymos system, at the same time compensating for any.

The broader interest lies in linking the observation to climatic, geophysical or environmental dynamics that extend well beyond the immediate event or location. Earth science is unusual in that its most important questions operate on timescales that no single research career can observe directly, making the archival record, whether in ice, sediment, rock or satellite data, as important as any new measurement. Results that can be embedded in that record, and that either confirm or challenge the patterns it reveals, carry disproportionate scientific weight.

This pair of manoeuvres will be followed by thee smaller ‘transition’ manoeuvres towards the end of the month that will reduce Hera’s relative velocity with respect to the Didymos. Asteroid Dimorphos, rotating around its parent body Didymos, is the first Solar System object to have been transformed by human action.

Because the account originates with ESA Space News, it functions best as a primary institutional report that is close to the data and operations, not as independent scientific validation. Institutional communications are produced by organizations with legitimate interests in presenting their work in a favorable light, which does not make them unreliable but does make them partial. Details that complicate the narrative, including instrument limitations, unexpected failures and results below projections, tend to be minimized relative to progress messages. Technical documentation and peer-reviewed publications, where they exist, provide the complementary layer that institutional releases cannot substitute.

The next step is to place the result inside longer time series and to compare it with independent instruments and independent sites. Earth system observations gain most of their interpretive power from network density and temporal depth, not from any single measurement however precise. Model simulations that assimilate the new data will help clarify whether the observation fits comfortably within known natural variability or represents a shift that existing models do not reproduce.

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