We report the occasional detection of negative pickup ions by the Shuttle Potential and Return Electron Experiment (SPREE) in the shuttle payload bay during the first Tethered Satellite System (TSS 1) mission. These ions appear as arch-like structures of enhanced fluxes in energy versus time spectrograms for the SPREE electron zone looking in the plane perpendicular to the Earth's magnetic field. Maximum energies of ~56 eV were measured when the sensor looked closest to the shuttle ram direction. Empirically, the energy of associated spectral peaks decreases as cos2 &xgr;, where &xgr; is the angle between the sensor look direction and the projection of the shuttle's velocity onto the plane perpendicular to the magnetic field. These signatures may be found under day or night conditions and always in conjunction with positively charged pickup ions generated as a result of firings by the L5D and/or R5D vernier thrusters. We show that positive ion contamination and accelerated electrons cannot be the responsible agents. Observed spectral characteristics are most easily explained as either NO2- or MMH- ions created near the shuttle and accelerated by the motional electric field to energies detectable by SPREE.¿ 1997 American Geophysical Union