A new layer of silicon sensors is being tested at CERN before being sent to the International Space Station
Written by:
Paola Catapano
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Suspended in the path of a proton beam from CERN’s Super Proton Synchrotron (SPS) was an unusual target: a large silicon tracker destined for space. Known as “Layer-0”, this new layer of silicon sensors will be mounted on top of the Alpha Magnetic Spectrometer (AMS) while it orbits Earth on the International Space Station (ISS). The additional tracker, assembled at CERN, will increase the detector’s particle acceptance rate by 300%, helping the AMS make the most of its remaining years in space before the planned end of the ISS programme in 2030.
From 28 June to 27 July at the EHN1 facility in CERN’s North Area, Layer-0 was hung from a robotic arm that moved it through more than 700 positions as it was hit by the SPS beam. Fully automated and synchronised with the detector data acquisition, the movements ensured that all of the tracker’s sensors were exposed to the stream of protons. This allowed the team to precisely scan the detector plane, mapping the response and position of each sensor and confirming the functionality of the detector. Further data is still being analysed.
“This was our last chance before CERN shuts down all the beams for LS3,” says Corrado Gargiulo, CERN-AMS Chief Engineer. “It is the first time that such a robotic arm has been used here in the North Area, marking a step towards using robotic and automated systems for handling detectors in CERN’s underground areas.” This effort will help with the development of technologies envisaged for potential future detectors, including the Future Circular Collider.
Exposing detectors to particle beams for calibration is standard practice in particle physics, but for the AMS, the exercise is particularly important. Layer-0 is three metres in diameter and will sit on top of the nine existing tracker layers, which are about one metre across. To correctly align the new and existing layers, the exact position of each of its 768 sensors must be known within a few micrometres, less than the width of a human hair.
Only a few milestones remain before Layer-0 can leave Earth. Having already passed extensive vibration and thermal-vacuum tests, Layer-0 will now undergo a final acceptance test at INFN–University of Perugia in Italy until 30 August, followed in October by the last of a series of measurements performed at CERN.
In January 2027, the new tracker is expected to fly from Geneva airport directly to the Kennedy Space Center on a commercial cargo plane. Its final journey to the ISS is planned for April, aboard a dedicated SpaceX Cargo Dragon. It will travel together with a new PDS (power distribution system) radiator, forming the largest single scientific payload ever carried by a Dragon spacecraft. This replacement radiator is vital for the AMS, as it will help restore the entire detector to its intended operating temperature following the performance degradation of the previous radiator over several years of operation in space.
Installing the new equipment in orbit will present challenges of its own. A series of preparatory spacewalks will be required beforehand to install the interface that will “receive” the new layer. Extensive astronaut training is ongoing at the Neutral Buoyancy Laboratory in Houston, one of the world’s largest indoor pools, with Gargiuloassisting in the simulation of the installation. By May 2027, mechanical and power connections are expected to be completed during further spacewalks, bringing the new system fully online.
With its new silicon tracker and radiator, the AMS is preparing for a second decade of cosmic-ray exploration from space, ready to continue its mission throughout the final years of the ISS.
Facts Only
* Layer-0, a new layer of silicon sensors, is being tested before launch to the International Space Station (ISS).
* Layer-0 will be mounted on top of the Alpha Magnetic Spectrometer (AMS) while it orbits Earth.
* The additional tracker increases the AMS particle acceptance rate by 300%.
* Layer-0 was tested at the EHN1 facility in CERN from June 28 to July 27.
* The testing involved moving Layer-0 through more than 700 positions under a proton beam.
* This movement ensured all sensors were exposed to the proton stream and allowed for scanning of the detector plane.
* Alignment requires knowing the exact position of each of the 768 sensors within a few micrometres.
* Final acceptance testing is scheduled until August 30 at INFN–University of Perugia.
* The final measurements will occur at CERN in October.
* In January 2027, Layer-0 is expected to travel from Geneva to the Kennedy Space Center.
* The journey to the ISS is planned for April aboard a SpaceX Cargo Dragon.
* Layer-0 travels with a new PDS radiator.
* Installation in orbit requires preparatory spacewalks and astronaut training.
* Mechanical and power connections are expected to be completed by May 2027.
Executive Summary
A new layer of silicon sensors, designated Layer-0, is being tested at CERN before being installed on the Alpha Magnetic Spectrometer (AMS) orbiting the International Space Station (ISS). This additional tracker is intended to increase the detector’s particle acceptance rate by 300%, allowing the AMS to maximize its operational time remaining before the ISS program concludes in 2030. The testing involved moving Layer-0 through over 700 positions under a proton beam at the EHN1 facility from June 28 to July 27. This process confirmed the functionality and position of the sensors by precisely scanning the detector plane.
Further steps involve final acceptance testing at INFN–University of Perugia until August 30, followed by measurements at CERN in October. The tracker is scheduled to fly to the ISS in January 2027 via a commercial cargo plane, ultimately attaching alongside a new Power Distribution System (PDS) radiator. This radiator replacement is essential to restore the AMS to its intended operating temperature following performance degradation over several years in space. Installation in orbit will require preparatory spacewalks and astronaut training.
Full Take
The narrative centers on extending the operational lifespan and enhancing the scientific utility of an existing space-based instrument, driven by necessity before planned program end dates. The focus shifts from in-situ experimentation to orbital deployment of complex hardware, necessitating rigorous pre-flight calibration protocols. A key tension exists between ground-based testing—which relies on robotic systems and particle beam exposure to map micron-level sensor positions—and the physical realities and logistical complexity of orbital installation.
The pattern observed is a necessary escalation of complexity in space science: new components are developed, heavily tested under extreme conditions (particle beams, vacuum), and then integrated via complex mechanical processes (spacewalks) for mission extension. The necessity of robotic handling and automated synchronization in the testing phase points toward a growing trend in leveraging automation to manage sensitive detector systems in inaccessible environments, extending beyond the initial physical constraints of spaceflight.
The implications involve balancing rigorous ground-based verification against the inherent risks introduced by bringing sophisticated hardware into orbit. Questions arise about whether the emphasis on incremental functional tests overshadows deeper consideration of long-term orbital system resilience and the potential cascading effects of mechanical and power integration in microgravity environments. What role does the development of automated handling systems, demonstrated here for CERN detectors, play in future deep-space infrastructure deployment?