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We provide the first direct observations of interstellar H+ and He+ pickupions in the solar wind from 22 AU to 38 AU. We use the Vasyliunas and Siscoemodel functional form to quantify the pickup ion distributions, and while thefit parameters generally lie outside their physically expected ranges, thisform allows fits that quantify variations in the pickup H+ properties withdistance. By ~20 AU, the pickup ions already provide the dominant internalpressure in the solar wind. We determine the radial trends and extrapolate themto the termination shock at ~90 AU, where the pickup H+ to core solar winddensity reaches ~0.14. The pickup H+ temperature and thermal pressure increasefrom 22-38 AU, indicating additional heating of the pickup ions. This producesvery large extrapolated ratios of pickup H+ to solar wind temperature andpressure and an extrapolated ratio of the pickup ion pressure to the solar winddynamic pressure at the termination shock of ~0.16. Such a large ratio hasprofound implications for moderating the termination shock and the overallouter heliospheric interaction. We also identify suprathermal tails in the H+spectra and complex features in the He+ spectra, likely indicating variationsin the pickup ion history and processing. Finally, we discover enhancements inboth H+ and He+ populations just below their cutoff energies, which may beassociated with enhanced local pickup. This study serves to document therelease and as the citable reference of these pickup ion data for broadcommunity use and analysis.

Interstellar Pickup Ion Observations to 38 AU