First time accepted submitter deathcow writes "After forty years, a fresh perspective on old Pioneer data leads to new conclusions as to why the Pioneer probes are decelerating. Many theories to the slowing probes have persisted over the years — was it gravity? some type of unforeseen radiation? dark matter? Thanks to the data backup preservation efforts of a NASA Ames Research engineer, mountains of old telemetry data were still available for studying this curious anomaly."