SH41E-2403
Observing the Interstellar Neutral He Gas Flow with a Variable IBEX Pointing Strategy
Thursday, 17 December 2015
Poster Hall (Moscone South)
Trevor Leonard1, Eberhard Moebius2, Maciej Bzowski3, Stephen A Fuselier4,5, David Heirtzler6, Marzena A. Kubiak3, Harald Kucharek6, Martin A Lee2, David J McComas4,5, Nathan Schwadron2 and Peter Wurz7, (1)University of New Hampshire Main Campus, Durham, NH, United States, (2)University of New Hampshire, Institute for the Study of Earth, Oceans and Space, and Department of Physics, Durham, NH, United States, (3)Space Research Center Polish Academy of Sciences, Warsaw, Poland, (4)Southwest Research Institute, San Antonio, TX, United States, (5)University of Texas at San Antonio, Department of Physics & Astronomy, San Antonio, TX, United States, (6)University of New Hampshire, Durham, NH, United States, (7)University of Bern, Bern, Switzerland
Abstract:
The Interstellar Neutral (ISN) gas flow can be observed at Earth’s orbit due to the motion of the solar system relative to the surrounding interstellar gas. Since He is minimally influenced by ionization and charge exchange, the ISN He flow provides a sample of the pristine interstellar environment. The Interstellar Boundary Explorer (IBEX) has observed the ISN gas flow over the past 7 years from a highly elliptical orbit around the Earth. IBEX is a Sun-pointing spinning spacecraft with energetic neutral atom (ENA) detectors observing perpendicular to the spacecraft spin axis. Due to the Earth’s orbital motion around the Sun, it is necessary for IBEX to perform spin axis pointing maneuvers every few days to maintain a sunward pointed spin axis. The IBEX operations team has successfully pointed the spin axis in a variety of latitude orientations during the mission, including in the ecliptic during the 2012 and 2013 seasons, about 5 degrees below the ecliptic during the 2014 season, and recently about 5 degrees above the ecliptic during the 2015 season, as well as optimizing observations with the spin axis pointed along the Earth-Sun line. These observations include a growing number of measurements near the perihelion of the interstellar atom trajectories, which allow for an improved determination of the ISN He bulk flow longitude at Earth orbit. Combining these bulk flow measurements with an analytical model (Lee et al. 2012 ApJS, 198, 10) based upon orbital mechanics improves the knowledge of the narrow ISN parameter tube, obtained with IBEX, which couples the interstellar inflow longitude, latitude, speed, and temperature.
