The Van Allen radiation belts of Earth tested by Slovak detector.

The space probe JUICE, which launched towards Jupiter in April 2023, returned to its home planet Earth in August 2024 after following an elliptical orbit around the Sun, for its first gravitational assist. Close flybys around planets in our solar system, also known as “gravity slingshots,” will accelerate the probe to reach Jupiter by July 2031. Three more gravitational assists will be required; Venus providing the next assist, followed by two more assists by Earth.

Last year’s close flyby of Earth at an altitude of 6840 km above the Pacific Ocean was also an opportunity to test and calibrate several scientific instruments on the probe. Among them was the particle instrument PEP, which includes the anticoincidence detector ACM, constructed at the Institute of Experimental Physics SAS in Košice, supported by PECS-Slovakia access program to the European Space Agency (ESA).

“The role of the ACM detector is detection of energetic electrons in Jupiter’s magnetosphere, which can deeply penetrate the shielding of scientific instruments. The ACM detector will allow these disruptive electrons to be distinguished from low-energy plasma particles, which is necessary for obtaining high-quality scientific data,” said Ján Baláž, designer of detector from the Institute of Experimental Physics SAS.

Part of the close flyby around Earth was a double transit of he probe through the outer Van Allen radiation belt, where Earth’s magnetic field traps high-energy electrons. Recent data analysis and calibration with the onboard radiation monitor RADEM confirmed that the ACM detector is doing exactly what it was designed to do: reliably detecting energetic electrons and their secondary products, which penetrate deeply into the PEP apparatus.

“During this phase of the flight, the ACM detector operated with a single energy threshold of 90 kilo-electronvolts (keV). We plan to perform even higher-quality calibration by scanning energy thresholds across its entire range from 54 keV to 320 keV. However, Venus won’t assist us with this, as it doesn’t have a magnetic field and therefore, no Van Allen radiation belts. So we will have to wait for the next flyby of Earth in September 2026,” said the scientist.

Source: SAS news