The European Space Agency has switched on its Ramses planetary defence spacecraft for the first time, marking a major milestone ahead of its planned 2028 launch. The ESA-JAXA mission is being developed to rendezvous with asteroid Apophis before the object makes an exceptionally close pass by Earth in April 2029.
The first integrated power-up took place at OHB Italia’s facilities in Milan, where the spacecraft’s Core Module is being assembled. Engineers powered the onboard computer and connected subsystems together, allowing them to begin testing how the spacecraft’s systems communicate and operate as an integrated vehicle rather than as separate components.
ESA said the spacecraft’s Mass Memory Unit, Power Conditioning and Distribution Unit and several Remote Terminal Units were among the systems involved in the first integrated switch-on. Individual components had already undergone testing, but the latest milestone represents the beginning of full spacecraft-level functional testing.
The timing is particularly important because Ramses is being developed on an unusually compressed schedule. ESA says the spacecraft needs to reach space by spring 2028 to arrive at Apophis in February 2029, roughly two months before the asteroid’s closest approach to Earth.
Ramses Will Watch Apophis During Its Close Earth Flyby
Asteroid 99942 Apophis is roughly 375 meters across and will pass about 32,000 kilometers above Earth’s surface on April 13, 2029. Astronomers have ruled out an impact with Earth, but the encounter remains exceptionally rare for an object of Apophis’ size.
Ramses will arrive before the flyby and accompany Apophis as Earth’s gravity affects the asteroid. Scientists expect the encounter could alter its rotation and potentially trigger surface disturbances such as landslides or other changes, providing an unusual opportunity to observe how a near-Earth asteroid responds to strong tidal forces.
The spacecraft will conduct observations before, during and after the close approach. By comparing measurements across the encounter, researchers hope to better understand Apophis’ shape, surface, rotation, orbit and internal properties, including characteristics such as density, porosity and structural cohesion.
Those measurements have implications beyond Apophis itself. Understanding how an asteroid responds to external forces can help researchers assess future planetary-defence missions, particularly when determining how a potentially hazardous asteroid could be deflected if one were discovered on an impact trajectory.
Ramses is also part of a broader international effort to study Apophis. JAXA is providing key spacecraft elements, including lightweight solar arrays and an infrared imager, while its H3 rocket is planned to launch the mission. The collaboration builds on previous ESA-JAXA cooperation, including the Hera asteroid mission.
The mission will not be the only spacecraft observing Apophis. NASA’s OSIRIS-APEX, the extended mission of the former OSIRIS-REx spacecraft, is also heading toward the asteroid and is expected to arrive after the 2029 Earth flyby. That timing could provide complementary observations of the asteroid after its close encounter with Earth.
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ESA is assembling Ramses in parallel modules to save time. While the Core Module is being developed in Italy, the Propulsion Module is being prepared at ArianeGroup’s Orbital Propulsion Centre in Germany. The two sections are scheduled to be joined next spring before the spacecraft enters its pre-flight testing phase.
The mission will then face a series of demanding tests designed to reproduce launch and space conditions. ESA plans to conduct thermal-vacuum testing and a full mission simulation before Ramses can be cleared for its 2028 launch aboard Japan’s H3 rocket.
The first switch-on therefore marks more than simply applying power to a spacecraft. It moves Ramses from a collection of separately tested components into integrated system testing, providing engineers with an early opportunity to identify and resolve problems before the mission reaches its critical launch window.
For planetary defence, the importance of Ramses lies in its ability to demonstrate how quickly a reconnaissance spacecraft can be developed and sent toward a near-Earth object. ESA says rapid reconnaissance would be an important part of responding to a genuine asteroid threat because scientists would first need detailed information about an object’s trajectory and physical structure before selecting a mitigation strategy.
With the first integrated switch-on now complete, Ramses has entered another stage of its accelerated development. The spacecraft still has assembly, integration and environmental testing ahead, but its systems are beginning to operate together as ESA and JAXA prepare for a rare encounter with Apophis in 2029.
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