Space exploration demands high performance on-board computers with low power requirements that can survive the rigours of aggressive radiation. The EU-funded APEX project has developed the advanced technologies needed to design an ultra-reliable processor for future space missions as far away as Saturn and Jupiter.
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The performance capabilities of space-grade processors are currently inadequate for the increasing demands of navigation, faultless manoeuvres and high-rate science data processing required for space exploration missions. Processors developed by ARM Ltd, coordinator of the APEX project, offer high performance on a constrained energy budget here on Earth, where they power most smartphones and tablets.
However, ARM processors lack resistance to high radiation and the ability to cope with the increasingly demanding functionalities required in space. The APEX (Advanced processor core for space exploration) project addressed these challenges. With the support of an EU Marie Skłodowska-Curie fellowship, Xabier Iturbe and his team of researchers "developed sufficient levels of resilience in ARM processors to withstand high levels of radiation and provide extremely long life, the fellow explains.
Exploration for signs of life
Iturbe started the project in NASAs Jet Propulsion Laboratory, where he worked on the CIRIS spectrometer. The second phase was carried out at the host institute ARM in Cambridge, the UK.
The search for life beyond Earth is a significant part of NASAs space programme and involves using on-board science instruments to analyse the composition of material collected in remote locations of our Solar System.
As part of the bid to develop space-qualified on-board computers with advanced capabilities, the APEX project designed a complete System-on-Chip (SoC) around an ARM processor, integrating the hardware support and software routines for science data processing, instrument calibration and housekeeping as well as on-board communications. The APEX-SoC was used with the Compositional InfraRed Imaging Spectrometer (CIRIS), a new generation of lightweight, rugged NASA instruments, designed to search for life on the icy moons of Jupiter and Saturn.
Coping with harsh radiation is possible thanks to two mechanisms in the APEX-SoC. First, a dedicated data processing stage eliminates most of the distortion provoked by radiation hits in the CIRIS photo detectors. Second, a set of fault-tolerant features implemented in the SoC detect and handle radiation-provoked upsets in the overall system. For instance, the SoC integrates two data processing stages that can be used to process data from two different CIRIS photo detectors in parallel, or to detect radiation-provoked upsets when they process data from the same photo detector. This technique allows for dynamic balancing between performance and reliability in different mission situations, Iturbe points out.
The APEX-SoC quadruples the performance of the previous generation CIRIS controller, and can process data from as many as 100 photo detectors, compared to only 25 previously. Furthermore, the APEX-SoC consumes 40 % less energy and can cope with up to 3 500 radiation hits per second.
Future space ventures
To satisfy reliability requirements in future NASA space exploration missions, APEX researchers built a radiation-tolerant ARM triple core lock-step processor that enables error detection and correction within microseconds current state-of-the-art technology takes 1 millisecond. Moreover, they implemented a novel high-resilience execution mode to enable ARM cores to execute high-criticality software routines with the highest levels of reliability. Importantly, the developed solution leverages the use of commercial technology to reduce manufacturing costs and increase performance.
Bringing space technology to Earth
Closer to daily life, the APEX processor can help keep pace with the needs of the ever-growing connected global infrastructure, which largely depends on space assets such as telecom satellites. Another possibility is as an enabler technology for the Internet of Space, where a myriad of cooperating satellite constellations will provide faster Internet access on Earth. As a first attempt to validate our technology in a real space environment, we are partnering with ESA to fly APEX processor-powered CubeSats designed by universities, says Iturbe.
Vast improvements in ARM processors tailored for the harsh space environments promise to create an extensive ecosystem of researchers and engineers providing state-of-the-art computing technologies. These could also be used in airborne and terrestrial applications that require high levels of reliability, including autonomous vehicles and Industry 4.0 robotics.
APEX has pioneered the development of a radiation-tolerant ARM processor and contributed to broadening the ARM ecosystem, creating synergies between communities as diverse as space scientists and commercial mobile developers, says Iturbe.
The technologies developed by Iturbe and his team will be crucial to future space explorations, and their commercial potential here on Earth in the meantime is considerable.