Planetary Defence: ESA's Hera Mission

Riyam Ojaimi
Jul 11
3 min read

In an era where the boundaries of human ambition stretch beyond the atmosphere, a silent threat looms in the vastness of space: asteroids, remnants of the solar system’s violent infancy, capable of unleashing devastation on an unimaginable scale. On October 7, 2024, the European Space Agency (ESA) launched the Hera mission, a pioneering endeavor not merely of exploration, but of survival. This spacecraft, bound for the distant asteroid system of Didymos and Dimorphos, carries the weight of humanity’s hope to master the art of planetary defense.

The Imperative of Planetary Defense

The specter of an asteroid impact is no longer confined to speculative fiction. Historical evidence, from the dinosaur-extinguishing Chicxulub event to the 1908 Tunguska explosion, underscores the destructive potential of near-Earth objects (NEOs). While the likelihood of a catastrophic collision remains statistically low, the consequences demand proactive measures. Hera emerges as a critical response to this challenge, building on the foundation laid by NASA’s Double Asteroid Redirection Test (DART) mission. In 2022, DART successfully struck Dimorphos, the smaller companion of the Didymos asteroid, altering its orbit by approximately 32 minutes - a proof of concept for kinetic impact as a deflection strategy.

Hera’s role is to conduct a forensic analysis of this celestial experiment. Scheduled to reach the Didymos-Dimorphos system in late 2026, the mission will scrutinize the aftermath of DART’s impact, examining the crater morphology, ejected debris, and the altered dynamics of Dimorphos’ orbit. This is not a mere academic exercise; it is a blueprint for safeguarding Earth against future threats. The data gathered will inform models of asteroid behaviour under impact, accounting for variances in composition - whether solid rock or loosely bound rubble piles - and refining techniques to mitigate risks posed by NEOs.

Scientific Precision in the Void

Equipped with cutting-edge instrumentation, Hera will deliver unprecedented insights into Dimorphos, a body just 160 meters across. High-resolution imaging will map surface changes down to centimeter-scale detail, while radar systems probe subsurface structures. Accompanying the main spacecraft are two CubeSats, Milani and Juventus, tasked with complementary observations of mineral composition and gravitational anomalies. These tools will yield a comprehensive dataset, revealing how the asteroid’s mass and internal structure responded to DART’s collision, and whether secondary hazards, such as debris fields, were created.

The stakes of this scientific endeavor extend beyond immediate findings. Each piece of information enhances predictive capabilities for asteroid deflection, ensuring that future interventions are not blind gambles but calculated strategies. With thousands of NEOs yet to be fully cataloged, the urgency of such knowledge cannot be overstated. Hera stands as a testament to the foresight required to transform vulnerability into resilience.

A Unified Global Endeavor

Hera exemplifies the power of international collaboration in confronting existential challenges. Led by ESA, the mission integrates contributions from over 18 European nations, alongside partnerships with NASA, which spearheaded DART and supports data analysis, and Japan’s JAXA, bringing expertise from asteroid exploration missions like Hayabusa2. This collective effort transcends borders, uniting diverse expertise under a singular mission to protect the planet.

The journey itself showcases engineering prowess. Launched on a Falcon 9 rocket, Hera embarks on a trajectory spanning over 6.5 million kilometers, including a gravitational assist from Mars in 2025. This flyby will not only optimize the spacecraft’s path but also enable observations of Mars’ moon Deimos, adding scientific value to the voyage. The precision required to rendezvous with a target as small as Dimorphos speaks to the advancements in navigation and autonomous systems driving modern space exploration.

The Gravity of Hera’s Purpose

Beneath the technical achievements lies a profound reality: Hera embodies humanity’s determination to endure. The mission confronts the inherent fragility of existence on a planet exposed to cosmic hazards, pushing the boundaries of what can be achieved through ingenuity and resolve. It serves as a reminder that while space may be indifferent, humanity possesses the capacity to anticipate and counteract its dangers.

As Hera approaches its destination, the mission will span six months of intensive study starting in December 2026, transmitting data that could shape planetary defense for generations. Beyond immediate outcomes, it paves the way for future initiatives, from advanced deflection technologies to potential asteroid resource utilization. The implications are vast, touching on security, exploration, and even economic frontiers.