The spacecraft Europe is building to meet asteroid Apophis during its rare close pass by Earth on Friday, April 13, 2029, has been switched on for the first time. The European Space Agency said on Sept. 23 that engineers at prime contractor OHB Italia powered up the spacecraft's On-Board Computer together with its integrated subsystems, according to ESA's announcement of the first switch-on. The agency called it a major milestone in a time-critical schedule for the mission, which ESA is carrying out with Japan's space agency.

The flyby's date has made Apophis a social media favorite, but there is no danger behind the Friday the 13th coincidence. In 2021, NASA's analysis ruled out any impact risk from Apophis for at least 100 years.

What the flyby offers instead is a rare science opportunity. Apophis, roughly 1,100 feet (340 meters) across, will pass within about 20,000 miles (32,000 kilometers) of Earth's surface, closer than some high-altitude satellites, according to NASA's OSIRIS-APEX mission page. Ramses is designed to study how Earth's gravity affects the asteroid during that encounter, knowledge that matters for planetary defense.

First Power-Up in a Milan Cleanroom

The switch-on took place in the Milan cleanroom of OHB Italia, where the spacecraft's Core Module, containing its main electronics, is being assembled. Key units were mounted inside the module's U-shaped body and linked by cabling known as the harness.

"For the first time we were able to apply power to Ramses's On-Board Computer," said Ramses lead engineer Ingo Gerth. He explained that the individual units had been tested before, but only on their own. Now the team can send commands through the computer to each subsystem and check how they perform together.

The connected systems include the Mass Memory Unit for data storage, the Power Conditioning and Distribution Unit that delivers power throughout the spacecraft, and Remote Terminal Units that convert instrument outputs into digital data for the computer.

ESA Ramses project manager Paolo Martino said everything before had been paper calculations, simulations or unit tests, "but now we have an actual spacecraft."

A Deadline Set by Orbital Mechanics

Most space missions take many years to move from contract to launch. Ramses does not have that luxury. ESA said the spacecraft must reach space by spring 2028 to rendezvous with Apophis as it passes Earth, which leaves less than three and a half years from contract signing to liftoff.

To save time, engineers are building the spacecraft in two parts at once. The Core Module in Italy is being assembled around a dummy version of the central structure. Meanwhile, the Propulsion Module, with its actual carbon-fiber reinforced-polymer core, is being fitted with propellant tanks, sensors and actuators at ArianeGroup's Orbital Propulsion Centre in Lampoldshausen, Germany.

The two modules are scheduled to be joined next spring at ESA's ESTEC Test Centre in Noordwijk, the Netherlands, where pre-flight testing begins. ESA system engineer Franco Perez Lissi said one of the toughest steps will be a thermal vacuum test, in which the complete spacecraft operates continuously in space-quality vacuum for two to three weeks. Ramses and two accompanying CubeSats must be ready to launch on a Japanese H3 rocket, provided by the Japan Aerospace Exploration Agency, in spring 2028.

That schedule leaves little margin. A problem found late in testing would leave limited time for fixes, because the flyby date cannot move.

The Science Behind the Close Pass

Apophis was discovered in 2004 and was briefly identified as one of the most hazardous asteroids that could strike Earth, after early calculations left small chances of impact in 2029, 2036 and 2068. Further tracking ruled out each scenario. In March 2021, radar observations and refined orbit analysis eliminated the last remaining 2068 possibility.

"A 2068 impact is not in the realm of possibility anymore," Davide Farnocchia of NASA's Center for Near-Earth Object Studies, managed by the Jet Propulsion Laboratory in Southern California, said when NASA announced the analysis.

NASA says Earth's gravity is expected to alter the asteroid's orbit, change how fast it spins and possibly cause quakes or landslides that reshape its surface. Watching those effects up close could help researchers understand how asteroids like Apophis are built, information that would matter if a hazardous asteroid were ever found on a collision course.

NASA is sending its own spacecraft as well. OSIRIS-REx, which delivered samples from asteroid Bennu in 2023, has been renamed OSIRIS-APEX and redirected to Apophis, with a rendezvous planned for mid-2029, after the flyby. Ramses is designed to reach the asteroid as it approaches Earth, so together the missions could document Apophis around the encounter and in the months that follow.

Keeping the Hype in Perspective

Readers will likely see more Friday the 13th content as 2029 approaches. The facts are straightforward: Apophis will not hit Earth in 2029, and NASA's analysis found no impact risk for at least a century. Claims suggesting otherwise are not supported by agency data, and no action is needed by the public.

What remains uncertain is engineering, not safety. Ramses still has to pass integrated testing, join its two modules, and launch on time. ESA has not reported any problems, but the schedule leaves little room for delays. The next milestone to watch is the joining of the two modules at ESTEC next spring.

What Readers Want to Know

What happened with the Ramses spacecraft?

ESA said on Sept. 23 that engineers powered up Ramses' On-Board Computer together with its integrated subsystems for the first time at OHB Italia's facility in Milan.

Will asteroid Apophis hit Earth on Friday, April 13, 2029?

No. NASA concluded in 2021 that there is no risk of Apophis impacting Earth for at least 100 years.

How close will Apophis come to Earth?

NASA says the roughly 1,100-foot (340-meter) asteroid will pass within about 20,000 miles (32,000 kilometers) of Earth's surface.

When will Ramses launch?

ESA says Ramses and two CubeSats must be ready to launch on a Japanese H3 rocket in spring 2028.

What will Ramses study?

The mission is designed to observe how Earth's gravity affects Apophis during the close pass, including possible changes to its path, spin, and surface.

Is NASA also sending a spacecraft?

Yes. NASA's OSIRIS-APEX, formerly OSIRIS-REx, is headed to Apophis and is planned to rendezvous with it in mid-2029, after the flyby.