GPS particle detectors track space radiation over two decades

Researchers in China have created a record of space radiation flux by cross-calibrating particle detectors on 25 navigation satellites. This new dataset covers two complete solar cycles from 2000 to 2020. The information tracks the movement of high-energy electrons from the Sun that enter Earth’s atmosphere.

GPS satellites orbit 20,000 km above the planet and carry radiation sensors to monitor space weather. While these instruments are essential for understanding risks to satellite hardware, they were difficult to compare because they were not cross-calibrated. Data values often differed by several orders of magnitude between units, and different sensor models complicated the analysis.

To solve this, the team used the NS59 satellite as a reference point because it provided consistent measurements starting in 2004. By accounting for the Earth's magnetic field and magnetic local time, they successfully unified data from 24 of the 25 satellites. One satellite provided unreliable data and was excluded from the final set.

This method of cross-calibration is applicable to other sensors as well. The researchers confirmed that the same techniques work when combined with data from the BeiDou system and NASA’s Van Allen Probes. This improved data quality helps designers protect future satellites from solar electron interference and provides clearer insight into the solar processes driving these radiation cycles.