Hot ion plasmas from the cloud of neutral gases surrounding the space shuttle

Large intensities of hot positive ions are observed out to distances of several hundred meters from the space shuttle Challenger (Spacelab 2) with a plasma analyzer on board a small free‐flying satellite, the Plasma Diagnostics Package. This ion plasma is inferred to be generated by the charge exchange of ionospheric O+ ions with a large cloud of water molecules from the space shuttle. The measured ion density ranges from ∼30 to 104 H2O+ ions cm−3. The hot ion plasma forms an ion trail in the wake of the space shuttle. A model for the water vapor cloud provides the basis for density estimates as high as 109 H2O molecules cm−3 at a distance of 50 m from the space shuttle. Thus the space shuttle possesses a substantial coorbiting atmosphere.