In July 1969, just a few days after the first Moon landing, CERN's then Director-General, Bernard Gregory, sent the following message to NASA: "CERN, which investigates the smallest particles of the Universe, sends its sincerest congratulations to NASA, which investigates the largest particles, on the triumphant conclusion of the Apollo 11 mission". More than 50 years later, these two worlds collide as a CERN-based technology, Timepix, is being launched in Artemis I, the NASA mission heralding the next phase of human space exploration.
Stuart George, a physicist in NASA's Space Radiation Analysis Group (SRAG) and a CERN alumnus, is the person to talk to in order to understand how this detector technology landed in NASA's laboratories. During his time with CERN's Radiation Protection group as a Marie Skłodowska-Curie PhD student, Stuart cut his teeth on Medipix detectors, chips used for particle imaging derived from the ones used to track particle trajectories inside CERN's Large Hadron Collider. After his formative years with this versatile detector, he saw an opportunity at the University of Houston and then at NASA to apply the technology behind the Timepix detector (Medipix's cousin) to space.
Developed by the CERN-hosted Medipix2 collaboration, Timepix detectors are extremely small but powerful particle trackers capable of monitoring radiation in the environment. Particles interacting with its pixelated sensor can be classified according to their characteristic shape and tell scientists about the radiation spectrum in various environments, such as spacecrafts.
With humans venturing again outside of Earth's protective magnetosphere, the issue of radiation has become increasingly salient. "Back in Apollo's days, trips consisted of one or two weeks. Future missions are considering at least month-long stays," explains Stuart. "On such long missions, the radiation environment must be monitored in real time in order to mitigate radiation hazards such as space weather." Radiation detection technologies such as Timepix make it possible to measure the radiation dose received by crew members, to understand the in-vehicle environment and to design models to give personnel in space, spacecraft or lunar vehicles early-warning signals if they need to seek shelter and shield themselves.
Timepix detectors were initially flown as a tech demo on the International Space Station (ISS) in 2012 thanks to the efforts of teams at the University of Houston, the Institute of Experimental and Applied Physics in Prague and NASA's own SRAG. Since then, NASA's SRAG and Advanced Exploration Systems have developed the technology to support a variety of missions, instituting Timepix-based systems as standard dosimeters at NASA.
This October, we celebrated the 10-year anniversary of Timepix's deployment in the ISS. The chip is now a key part of NASA's new HERA radiation detector, which is included in the Artemis programme. Launched this week, Artemis I carried three Timepix chips on a HERA detector, and another one as part of the first deep space biology experiment. A system based on the Timepix chip is also included on Astrobotic's lander, one of the programme's first three robotic missions to the Moon, which will be launched in the first quarter of 2023. The system will provide real-time data about the radioactive environment of the lunar surface for the first time in history. "Timepix is lighter, more capable and more energy-efficient than other hardware. It is also resilient to both the strong vibrations and shocks of space launches and the high flux rates of deep space," adds Stuart.
Besides astronaut dosimetry, Timepix may be used to predict solar storms and other space events that could impact the Earth and its environment, disrupt telecommunications and cause power grid surges. "Harnessing Timepix to predict solar storms would pose more difficult challenges. While they are extremely reliable in their current form, Timepix chips would have to last five to ten years in space, live in a high-vacuum environment and resist extreme, sun-facing temperatures," says Stuart. Today, he and his teammates are working to make the chip more reliable and autonomous than ever.
