DOWNWARD-DEPLOYED TETHERED SATELLITE SYSTEMS, MEASUREMENT TECHNIQUES, AND INSTRUMENTATION - A REVIEW

Data describing spacecraft atmospheric interactions in the lower terrestrial thermosphere (altitude range between 90 and 200 km) are extremely limited due to the relative inaccessibility of this region to research vehicles. Atmospheric measurements in the lower thermosphere are sparse when compared with measurements on satellites at higher altitudes. Downward-deployed tethered satellites are being developed to allow access in a global sense to this important region of the atmosphere. This paper reviews a number of tethered satellite systems, emphasizing downward-deployed systems to measure properties in the lower thermosphere; the physics and chemistry of the lower thermosphere; the interactions of the lower thermosphere with high-velocity tethered satellites; and the performance capabilities of existing and new instrumentation to measure atmospheric, aerodynamic, and aerothermodynamic properties that include radiative emission (glow), magnetism, and the distribution of the neutral gas, excited species, ions, and electrons. It is concluded that these tethered satellite systems, when implemented, offer a unique opportunity to investigate regions of the atmosphere previously inaccessible to conventional satellites.