Instrument for differential ion flux vector measurements on Spacelab 2

The differential ion flux probe (DIF probe) is a scientific instrument capable of deconvolving a multiplicity of ion streams, differing in flow direction and/or energy, and independently determining the flow direction, current density, temperature, and energy of each stream. The original instrument concept was developed for laboratory investigations in the area of plasma dynamics and was reported [N. H. Stone, Rev. Sci. Instrum. 48, 1458 (1977). Since then, the DIF probe has been redesigned and developed into a flight instrument to provide measurements of disturbed plasma flow conditions within the terrestrial ionosphere. It has flown on the STS-3 Space Shuttle mission, on sounding rockets, and recently on the Spacelab-2 mission as part of the plasma diagnostics package (PDP) experiment. Herein, we discuss the unique design and operational characteristics required for the flight model of the DIF probe.