Searching for modifications to the exponential radioactive decay law with the Cassini spacecraft

TL;DR

This study uses Cassini spacecraft data to test if radioactive decay rates deviate from the exponential law based on Earth-Sun distance, finding no significant deviations within the tested range.

Contribution

It provides the first experimental constraints on potential distance-dependent modifications to radioactive decay laws using space-based measurements.

Findings

No significant deviations from exponential decay observed.

Set upper limits on decay rate modifications related to Earth-Sun distance.

Constraints improve previous terrestrial measurement bounds.

Abstract

Data from the power output of the radioisotope thermoelectric generators aboard the Cassini spacecraft are used to test the conjecture that small deviations observed in terrestrial measurements of the exponential radioactive decay law are correlated with the Earth-Sun distance. No significant deviations from exponential decay are observed over a range of 0.7 - 1.6 A.U. A 90% Cl upper limit of 0.84 x 10^-4 is set on a term in the decay rate of Pu-238 proportional to 1/R^2 and 0.99 x 10^-4 for a term proportional to 1/R.