Ramses wakes up as Europe powers its asteroid mission

The spacecraft Europe and Japan are sending to meet an asteroid has been switched on for the first time. ESA and JAXA confirmed that the Ramses spacecraft was powered up by its prime contractor OHB Italia in a Milan cleanroom, the first time its main electronics have run together as a single machine rather than as separate units on a test bench.

What was switched on

The Core Module holding all of Ramses's main electronics is being assembled at OHB Italia's cleanroom facility in Milan. Key units have been mounted inside the module's U-shaped body and wired together with the spacecraft harness, the dense cabling that connects every subsystem to the computer that commands them.

Ingo Gerth, the mission's lead engineer, said the team applied power to the On-Board Computer together with its integrated subsystems inside the spacecraft body for the first time. “Obviously these units have previously undergone individual testing, but this was by themselves in a void,” he said. “Now, for the first time we have been able to perform real integrated functional testing.”

Those subsystems include the Mass Memory Unit that stores the mission's data, the Power Conditioning and Distribution Unit that feeds electricity around the spacecraft, and the Remote Terminal Units that convert instrument outputs into digital data for the computer. Commands can now be sent to each of them to check that they perform as intended.

The deadline that cannot move

Ramses has to be in space by spring 2028 to reach Apophis as the asteroid passes Earth on Friday 13 April 2029. That gives the mission less than three and a half years from contract signature to lift-off, which is why the spacecraft is being built in two places at once: the Core Module in Italy around a dummy of the central cylindrical core, and the Propulsion Module, with the real carbon-fibre reinforced polymer core, at ArianeGroup's Orbital Propulsion Centre in Lampoldshausen, Germany, where propellant tanks, sensors, actuators and harness are being fitted.

Arnaud Bourdoux, Ramses functional architect, called the switch-on an exciting moment because these are the same system-critical units the team will turn on at the launch pad. Giuseppe Filomeno, project manager at OHB Italia, said the moment marked the first tangible confirmation that the integrated systems work together as intended.

Testing the whole spacecraft

The two modules are due to be mated next spring at ESA's ESTEC Test Centre in Noordwijk in the Netherlands, which starts the pre-flight test phase. Franco Perez Lissi, a systems engineer on the mission, said the thermal vacuum test will put the complete spacecraft in space-quality vacuum for two to three weeks while it operates continuously, and that the mission simulation test will run it through a sped-up version of everything from lift-off to end of mission. Ramses and its two CubeSats must be ready to launch on a Japanese H-3 rocket in spring 2028.

Paolo Martino, ESA's Ramses project manager, said the switch-on marks a completely new phase for the project, because everything before it was paper calculations, simulations or unit tests. “Now we have an actual spacecraft,” he said, “ready for our full-scale integrated system testing to begin.”

Our opinion

Planetary defence missions are usually sold on the drama of the asteroid, and Apophis supplies plenty: a rock the size of a cruise liner passing closer to Earth than the geostationary satellites. The engineering reality is duller and harder. Nothing about this mission can slip, because the target keeps to a schedule set by orbital mechanics rather than by a programme board, and a spacecraft that misses its window does not get a second date.

That is what makes the Milan milestone worth reading carefully. Building the core and the propulsion module in parallel, in two countries, is a deliberate compression of the schedule, and the switch-on is the point where the paper design becomes hardware that can actually be tested. It also matters that this is a joint ESA and JAXA mission with a Japanese launcher: planetary defence is one of the few areas where European and Japanese space budgets are pointed at the same problem, and Ramses is now the test of whether that alignment survives contact with a deadline.