Spoke 4 brings together Italian research institutions and industries to advance a new generation of detection and timing technologies for space missions. The activities focus on solid-state radiation sensors, photodetectors, gravitational reference systems, emerging instruments for space-weather monitoring, and innovative time–frequency references for deep-space exploration. All developments address the stringent mass, power, and environmental constraints typical of space applications.

A first area of work is dedicated to silicon-based particle detectors, where the Spoke is building a national supply chain capable of designing and producing high-granularity, low-power tracking sensors based on commercial semiconductor technologies. These devices combine advanced architectures – such as monolithic active pixel sensors and low-gain avalanche diodes – with custom readout and data-acquisition electronics. Alongside fabrication, the Spoke defines qualification strategies and carries out calibration and verification campaigns to assess performance and technology readiness.

A second line of activity focuses on SiPM-based detectors for ionizing radiation, used in applications ranging from terrestrial gamma-ray flashes to space-weather phenomena. The work includes optimizing sensor configurations, developing low-noise and rad-hard electronics, integrating prototypes, and performing comprehensive tests to evaluate their suitability for future missions.

Spoke 4 also develops a gravitational reference system for highly precise inter-satellite geodesy. The effort spans requirement analysis, system design, hardware procurement, and the testing of a prototype comprising the test mass and its electrode housing, with the goal of enabling more accurate monitoring of Earth’s water-mass distribution.

Another research direction addresses emerging technologies for observing Sun–Earth interaction phenomena, including innovative sensors for energetic neutral atoms, hard X-ray polarimetry, and plasma monitoring. The Spoke develops compact prototypes and assesses their performance with the aim of increasing technology readiness for space-weather monitoring missions.

Finally, the Spoke works on next-generation time and frequency references, developing microfabricated clock components based on optical frequency standards. These systems are designed to reduce size, weight, and power while improving synchronization capabilities for multi-detector observations and deep-space navigation.