Hera, launched on October 7, 2024, is en route to study the first asteroid to have its trajectory altered by human intervention. By gathering close-range data on Dimorphos, the asteroid impacted by NASA's DART mission in 2022, Hera aims to refine asteroid deflection as a viable planetary defense strategy.
The flyby, conducted on March 12, was a crucial part of Hera's deep-space journey, carefully planned by ESA's Flight Dynamics team. The spacecraft passed within 5000 km of Mars, utilizing the planet's gravitational field to redirect its course toward Dimorphos and its larger companion, Didymos. This maneuver significantly reduced Hera's travel time and conserved fuel.
Traveling at a speed of 9 km/s relative to Mars, Hera managed to observe Deimos from just 1000 km away. The spacecraft's imaging captured the far side of the moon, which remains largely unseen from Mars. With a diameter of 12.4 km and a surface blanketed in dust, Deimos is believed to be either the remnant of a massive impact on Mars or a captured asteroid.
"Our Mission Analysis and Flight Dynamics team at ESOC in Germany executed the gravity assist flawlessly," said ESA's Hera Spacecraft Operations Manager Caglayan Guerbuez. "They even refined the trajectory to ensure a close approach to Deimos, which required additional precision planning."
During the flyby, three of Hera's scientific instruments were activated:
- The Asteroid Framing Camera, a 1020x1020 pixel black-and-white imager, captured visible-light images for both navigation and scientific study.
- The Hyperscout H hyperspectral imager analyzed Deimos in 25 spectral bands extending beyond human vision, aiding in mineral composition characterization.
- The Thermal Infrared Imager, provided by JAXA, mapped surface temperatures at mid-infrared wavelengths, revealing data on surface roughness, particle size, and porosity.
"These instruments had been previously tested after Hera's launch, but this was their first real use on a distant, small celestial body," explained ESA Hera mission scientist Michael Kueppers. "Their performance exceeded expectations."
Hera Principal Investigator Patrick Michel, Director of Research at CNRS / Observatoire de la Cote d'Azur, added: "Other instruments, such as the PALT laser altimeter with its 20 km range, were not employed during this encounter due to the high speed and long distance involved. Additionally, instruments aboard Hera's CubeSats remain inactive until arrival at Dimorphos."
Hera also collaborated with ESA's Mars Express, a long-standing orbiter around the red planet, for joint observations of Deimos. Data from this flyby will support planning for the Martian Moons eXploration (MMX) mission, led by JAXA in partnership with NASA, CNES, DLR, and ESA. MMX aims to conduct comprehensive studies of Mars' moons and retrieve a sample from Phobos for return to Earth.
While Deimos is significantly larger than Hera's final destinations-Dimorphos (151 m across) and Didymos (780 m across)-the spacecraft is now on a precise trajectory toward them. A planned course correction in February 2026, followed by a series of rendezvous maneuvers starting in October 2026, will ensure Hera reaches the Didymos system in December of that year.
"This marks the first of many thrilling exploration phases for Hera," said ESA Hera mission manager Ian Carnelli. "In just 21 months, we will arrive at our target asteroids and begin an in-depth analysis of the only celestial body in the Solar System whose orbit has been altered by human effort."
Related Links
Hera at ESA
Asteroid and Comet Mission News, Science and Technology
| Subscribe Free To Our Daily Newsletters |
| Subscribe Free To Our Daily Newsletters |
