The Ionospheric Connections Explorer (ICON) payload includes an Ion Velocity Meter (IVM) to provide measurements of the ion drift motions, density, temperature and major ion composition at the satellite altitude near 575 km. The primary measurement goal for the IVM is to provide the meridional ion drift perpendicular to the magnetic meridian with an accuracy of 7.5 ms for all daytime conditions encountered by the spacecraft within 15° of the magnetic equator. The IVM will derive this parameter utilizing two sensors, a retarding potential analyzer (RPA) and an ion drift meter (IDM) that have a robust and successful flight heritage. The IVM described here incorporates improvements in the design and operation to produce the most sensitive device that has been fielded to date. It will specify the ion drift vector, from which the component perpendicular to the magnetic field will be derived. In addition it will specify the total ion density, the ion temperature and the fractional ion composition. These data will be used in conjunction with measurements from the other ICON instruments to uncover the important connections between the dynamics of the neutral atmosphere and the ionosphere through the generation of dynamo currents perpendicular to the magnetic field and collisional forces parallel to the magnetic field. Here the configuration and operation of the IVM instrument are described as well as the procedures by which the ion drift velocity is determined. A description of the subsystem characteristics, which allow a determination of the expected uncertainties in the derived parameters, is also given.

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Three spectrometers and associated experiments are described. The work reviewed comprises the early experimental phases of a program to develop a satellite infrared spectrometer capable of making radiometric measurements in the 15-micron carbon dioxide band needed for deduction of atmospheric temperature profiles. Initially, a simplified, breadboard spectrometer with four spectral channels was used to determine the temperature profile of the lower atmosphere from the ground. Next, a commercial spectrophotometer was modified and another determination of the atmospheric temperature profile was made using more spectral intervals. Instrument specifications for a balloon flight model spectrometer were aerived from these experiments. Following the model's fabrication, testing, and calibration, two high-altitude balloon flights were conducted to demonstrate that the atmospheric temperature profile could be ascertained from above the atmosphere.

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