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We present measurements of electron temperature (Te) made by a retarding potential analyzer and a Langmuir probe (both flush-mounted on the spin-stabilized satellite Explorer 31) to investigate the variation of Te around the satellite. Most of the time there is a Te variation, which repeats for given ionospheric conditions. The variation is strongly controlled by the angle between the velocity vector and the probe normal, Te usually being enhanced in the near wake of the satellite. Magnetic field control of Te, if it is present, is hidden by the stronger velocity vector control. Our results indicate that the magnitude of the Te enhancement in the wake does not depend on the average ion mass (M), although the electron density depletion in the wake is strongly correlated with M.

In a recent series of flights over the marginal ice zone in the Greenland Sea the Naval Research Laboratory demonstrated that millimeter wavelength radiometry can be used for the remote determination of sea ice edge properties under all weather conditions. The imaging measurements, obtained at 90 GHz (3.3 mm) and 140 GHz (2.1 mm) from high altitude through heavy cloud conditions, can be used to delineate the sea ice edge, to locate polynyas and leads, to measure ice concentration, to determine ice type, age, and thickness, and to quantify the sea surface wind and atmospheric properties. Sea ice images were also obtained at 220 GHz (1.4 mm) but only under clear atmospheric conditions. The location, movement, and concentration of the sea ice edge greatly affects the dynamics of ice-ocean circulation and air-sea interaction. This information is fundamental for accurate long-term weather prediction and for ship operations. These are the first measurements of sea ice ever obtained at 140 and 220 GHz.