TRACKER GUIDE & MISSION EXPLAINER
Hera Spacecraft Tracker: Didymos, Dimorphos and Planetary Defence
Hera is ESA's planetary-defence mission to the binary asteroid system Didymos and its small moon Dimorphos. The tracker above follows Hera's interplanetary trajectory with JPL Horizons ephemerides and displays current distance, light time and velocity.
The spacecraft launched on October 7, 2024 and is scheduled to rendezvous with Didymos in November 2026. Its investigation follows NASA's DART impact, which deliberately changed Dimorphos' orbit in September 2022.
Turning an impact into a measured experiment
DART demonstrated kinetic impact by striking Dimorphos, but remote observations cannot determine every physical detail. Hera will measure the moonlet's mass, shape, surface and interior, examine the impact site and refine knowledge of how efficiently momentum was transferred.
Those measurements help convert one successful demonstration into a better understood technique that could inform a future response to a hazardous asteroid. Didymos itself is not on a collision course with Earth.
How the tracker follows Hera
Horizons position and velocity vectors are sampled at set times and interpolated for the page. The visual cannot depict the tiny binary asteroid system at the same scale as the interplanetary route.
Rendezvous differs from a high-speed flyby: Hera must approach with a suitably small relative velocity for extended proximity operations. Official ESA updates explain the navigation and arrival sequence.
Educational questions
- How can a kinetic impact change an asteroid moon's orbital period?
- Why must mass be measured to understand momentum transfer?
- What makes navigation around a low-gravity binary system difficult?
- How will Hera's CubeSats complement the main spacecraft?
- Why does planetary defence require years of observation and preparation?
Limitations
The tracker does not report hazard probability, autonomous-navigation status or close-proximity operations. It is not an asteroid-warning service. Ephemeris values describe the spacecraft trajectory; ESA and recognised planetary-defence organisations provide official mission and risk information.
Why measuring the result matters
Changing an asteroid's motion is only useful if scientists understand how target size, structure and composition affect the outcome. A porous rubble pile can respond differently from a solid monolith. Hera's measurements of Dimorphos and the impact site will constrain those unknowns. The page therefore connects spacecraft navigation with experimental science: DART supplied the controlled action, telescopes measured the initial orbital change, and Hera will inspect the physical result at close range.
Frequently asked questions
Is Didymos dangerous to Earth?
The Didymos-Dimorphos system used for the DART and Hera experiment is not on a collision course with Earth.
What did DART change?
DART's impact shortened Dimorphos' orbital period around Didymos. Hera will measure the result in much greater detail.
Will Hera impact the asteroid?
Its primary mission is a rendezvous and detailed survey, not a repeat of the DART kinetic impact.
When will Hera arrive?
ESA currently gives November 2026 for rendezvous with Didymos.
Sources and further reading
Educational-use note: SpaceTracker.live is an independent educational website and is not an official mission-control service. Positions, paths, distances and pass predictions are computed from third-party orbital elements or ephemerides. They may be delayed or approximate and must not be used for navigation, collision avoidance or safety-critical decisions.
Last reviewed: August 21, 2026