Ivan J. Galysh

Wind Ion-drift Neutral Composition Suite cathode activation procedure and current–voltage characteristics

The Wind Ion-drift Neutral Composition Suite (WINCS) uses three BaO thermionic cathodes in three ion sources for its neutral air measurements. The cathode activation procedure, obtained in laboratory measurements on a series of stock WINCS cathodes, ensures optimum cathode emission and life. The procedure begins by heating the cathode to 300–500°C to evolve CO2 and other gaseous products of the binder and the BaCO3; then the cathode temperature is raised to above 900°C for breakdown to BaO and sintering some of the Ba into the tungsten substrate; finally, activation begins by applying a small extraction voltage to the anode in front of the cathode. After activation, the cathode is ready to operate with any selected anode voltage. Electron emission of the WINCS cathodes easily exceeds 1 mA, and the fraction transmitted through the WINCS anodes exceeds 10% as required for WINCS. A maximum electron kinetic energy of about 90 eV was established as safe, also providing optimal ionization efficiency.

Design of the microsatellites used in the atmospheric neutral density experiment

The Atmospheric Neutral Density Experiment (ANDE) is a series of four microsatellites that will study the atmosphere of the Earth from low earth orbit. Each microsatellite is based on a common design; however, each differs in the instrument payloads and the associated science and mission requirements. The primary mission objective is to provide total neutral density along the orbit for improved orbit determination of resident space objects. Each ANDE microsatellite has several secondary goals. It is the unique design of the microsatellites that allows this task to be accomplished. Each microsatellite is a compact, near perfect sphere; this reduces shape and drag errors so that the local density of the atmosphere can be determined by instantaneous tracking variations detected by very high accuracy laser and radar ranging whereby the spacecrafts themselves are the primary sensing instrument. The accuracy of the atmospheric density measurements inferred from the orbital tracking of ANDE microsatellites will be much greater than that achieved by similar experiments in the past or from any currently proposed. Many unique design challenges had to be overcome to achieve the necessary science, mission, and operational requirements as well as severe cost constraints. New methods for parts and assembly fabrication were sought out and implemented. These new methods allowed similar parts to function in each of the microsatellites despite the differences between them. In addition, the command and telemetry links used inexpensive COTS Ham radio transceivers while meeting all the International requirements for operations in the Amateur Satellite Service.