Hera Successfully Launched to Unveil the Aftermath of DART

On October 7, 2024, at 14:52 UTC, ESA’s Hera satellite was successfully launched on board a SpaceX Falcon 9 from SLC-40 at Cape Canaveral, Florida, USA. As the rocket lifted off, the spacecraft began ESA’s ambitious mission to study the consequences of DART‘s kinetic impact on Dimorphos, the moonlet orbiting the near-Earth asteroid Didymos. The targeted body is also the smallest asteroid ever visited by humankind.

Liftoff of @ESA’s Hera! pic.twitter.com/mMoNPzX0b6
— SpaceX (@SpaceX) October 7, 2024

Nearly two and a half minutes into the flight the first stage separated and the second one ignited, propelling Hera further into space. The second stage detached at T+01:16:00, releasing the spacecraft to start its mission. Given the performance requirements to launch Hera into an interplanetary transfer orbit, the first stage was not recovered for this mission. Thus, the B1061 booster concluded an important streak of 23 successful launches, including Crew-1, the first operational flight of Crew Dragon.

Understanding the dynamics of cosmic collisions

Earth has endured over three million impacts with celestial bodies over its geological history. Although the likelihood of a catastrophic asteroid impact is small, the consequences could be devastating.

AIDA (Asteroid Impact & Deflection Assessment) is an international initiative designed to tackle the challenges related to potentially hazardous Near-Earth Objects (NEOs). It involves the launches of two spacecraft: NASA’s Double Asteroid Redirection Test (DART) and ESA’s Hera mission. DART, successfully launched on a SpaceX Falcon 9 rocket, intentionally collided with Dimorphos (the moon of the near-Earth asteroid Didymos) on September 26, 2022, after a 10-month journey.

HERA and CubeSat render near asteroids. Credits: HERA mission — *Rendering of HERA and its CubeSats near the asteroids. Credits: ESA*

During AIDA’s second phase, Hera will reach the asteroid system to gather crucial data, allowing scientists to study the outcomes of the previous redirection test. Hera will provide further insight into the findings of the DART mission by closely analyzing the changes in Dimorphos’ orbit and surface after the impact. The data gathered will be critical for validating asteroid deflection techniques and understanding the long-term effects of kinetic impacts on celestial bodies.

The spacecraft will also showcase new technologies for deep space exploration. These include autonomous vision-based navigation and inter-satellite communication links connecting Hera to two CubeSats, Milani and Juventas.

Technical breakdown

After the jettison of the second stage, Hera began its two-year journey to the binary asteroid system. The spacecraft consists of a central box-shaped body of approximately 1.6 meters per side, weighing around 1,081 kg. This platform features 5-meter-long solar panels that provide power, as well as essential equipment for collecting data and communicating with Earth.

The Hera spacecraft inside the Maxwell chamber for electromagnetic compatibility testing, checking its systems can operate without harmful interference. — *Hera Spacecraft inside the Maxwell test chamber for electromagnetic compatibility testing. Credits: ESA*

Hera carries a total of 12 instruments, including two CubeSats, Milani and Juventas, which will be deployed to further study DART’s impact and the external and internal characteristics of the two asteroids.

The spacecraft relies primarily on its Asteroid Framing Camera to gather navigation data. Among the other instruments are the Thermal Infrared Imager (TIRI), which will chart the temperature of the surface, the Laser Rangefinder, designed to determine the distance to the surface, and the Spacecraft Monitoring Camera, tasked with observing the deployment of the CubeSats and inspect them.

HyperScout H will analyze the mineral composition of the asteroid, while the Deep Space Deployers (DSDs) will ensure the two CubeSats remain operational during the two-year cruise phase to Didymos. Additionally, the spacecraft carries inter-satellite links, Low and High Gain Antennas, and Startrackers.

Close-up image of the high-gain antenna on ESA's Hera spacecraft — *The high-gain antenna of ESA’s Hera spacecraft. Credits: ESA*

Hera has a high level of onboard autonomy, meaning that it will be able to process inputs from various sensors to understand its surroundings without continuous guidance from ground control.

The journey to the binary system

The spacecraft’s first major step will be a deep-space maneuver in November 2024, which will set the course for a Mars gravity assist in mid-March 2025. Another maneuver in February 2026 will direct Hera’s path toward the Didymos system.

In October 2026 the spacecraft will perform an ‘impulsive rendezvous’ to bring itself in proximity with the Didymos asteroid system, where it will enter orbit for its scientific mission. At the time of the rendezvous with the moonlet, Hera will be 195 million kilometers (1.3 Astronomical Units) away from Earth.

*Rendering of Hera orbiting between Didymos and Dimorphos. Credits: ESA*

Hera’s mission is of paramount importance in addressing potential future risks of collisions with other asteroids. ESA’s Near-Earth Object Coordination Center (NEOCC) collaborates with NASA’s Center for Near-Earth Object Studies (CNEOS) to predict the orbits of potentially hazardous celestial objects. By studying the aftermath of the DART impact, Hera will provide critical data that can improve our ability to deflect dangerous asteroids and refine our predictions, preparing us for future threats.

^{*Cover image credits: ESA}