 The Gehrels and Stone paper describing the measurement made a prediction, later confirmed, that the auroral emissions on Jupiter are cause by precipitating oxygen and sulfur ions.As a postdoc and then permanent scientist at Goddard, Gehrels worked on the GRIS balloon payload for high resolution (germanium detector) spectroscopy of gamma-ray sources.He first was involved in the proposal to NASA for the instrument, specializing in the design and techniques for background reduction.