Session
Technical Session V: The Year in Retrospect-- Missions that have been Achieved in the Past Year
Abstract
Between June 1999 and January 2003 three Starshine spacecraft were launched into low-earth orbits. Their lifetimes cover an extended period near the maximum of solar cycle 23. Two additional Starshine spacecraft are ready for launch near the minimum of solar cycle 23. The Starshine missions are especially suitable for estimating average upper atmospheric densities, since the orbits are approximately circular and the spacecraft are mirrored spheres for which ballistic coefficients are essentially independent of orientation with respect to the direction of motion. We have derived total neutral atmospheric mass densities along the Starshine spacecraft trajectories using quantities from their Two-Line Element sets (TLEs). We compare these densities with corresponding determinations by a semi-empirical model of upper atmospheric neutral densities developed at the Naval Research Laboratory. This model, NRLMSIS, has been formulated for both research and operational use from a database that now includes total mass densities from satellite accelerometers and orbit determinations, more recent temperatures from incoherent scatter radar, and molecular oxygen number densities from solar UV occultation. The Starshine orbits were not included in the NRLMSIS model formulation and thus provide independent validation of the modeled variations on time scales of days to months during a period of relatively high solar activity.
Presentation Slides
Upper Atmospheric Densities Derived From Starshine Spacecraft Orbits
Between June 1999 and January 2003 three Starshine spacecraft were launched into low-earth orbits. Their lifetimes cover an extended period near the maximum of solar cycle 23. Two additional Starshine spacecraft are ready for launch near the minimum of solar cycle 23. The Starshine missions are especially suitable for estimating average upper atmospheric densities, since the orbits are approximately circular and the spacecraft are mirrored spheres for which ballistic coefficients are essentially independent of orientation with respect to the direction of motion. We have derived total neutral atmospheric mass densities along the Starshine spacecraft trajectories using quantities from their Two-Line Element sets (TLEs). We compare these densities with corresponding determinations by a semi-empirical model of upper atmospheric neutral densities developed at the Naval Research Laboratory. This model, NRLMSIS, has been formulated for both research and operational use from a database that now includes total mass densities from satellite accelerometers and orbit determinations, more recent temperatures from incoherent scatter radar, and molecular oxygen number densities from solar UV occultation. The Starshine orbits were not included in the NRLMSIS model formulation and thus provide independent validation of the modeled variations on time scales of days to months during a period of relatively high solar activity.
