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FOV/Attitude

FOV/Attitude. What Are We Imaging?. Lunar Atmosphere – interaction with S.W. What criteria should be applied? Magnetosheath – interaction with S.W. Primary driver for aspect selection criteria Heliosphere–interaction of neutral ISM with S.W. Sample region small X-ray Background

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FOV/Attitude

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  1. FOV/Attitude

  2. What Are We Imaging? • Lunar Atmosphere – interaction with S.W. • What criteria should be applied? • Magnetosheath – interaction with S.W. • Primary driver for aspect selection criteria • Heliosphere–interaction of neutral ISM with S.W. • Sample region small • X-ray Background • A bonus, does not drive aspect selection criteria

  3. Magnetosheath Model • Bowshock/Magnetosheath model of Spreiter, Summers, & Alksne (1966) • Scaled by nominal Solar Wind • ρ=2.0 cm-3 • v=400 km/s • Exospheric Neutral Model • N(r)=25.0(10.0 RE/R)3 cm-3 • X-ray Emission proportional to • N(r)ρ(r,θ)[v(r,θ)2+3kBT(r,θ)/m]½

  4. Magnetosheath Model • Distances/sizes to scale • X-ray emission strength unnormalized • MP~11.95RE • BS~15.09RE

  5. Model FOV as f(t) Given (λ,µ) Baseline Instrument • Zenith telescope at selenographic (λ,µ) =tilted telescope at some other (λ,µ) • Incapable of pointing • Field of view diameter of 10° • Detector on at all times

  6. Lunar Model • Lunar Orbit • e=0.05490 • i=5.15° from the ecliptic • a~384,400 km ~60RE • dΩ/dt=19.35°/year (18.6 year precession period) • Moon • Obliquity=6.87° from orbit, 1.54° from ecliptic • ω=13.17635815 deg/day

  7. Lunar Model Consequences: • Cis-lunar space is not scanned evenly • LOS from moon can pass above/below the Earth-sun line • LOS from moon has nearly constant ecliptic latitude

  8. JPL DE405 ephemeris IDL implementation by Markwardt P.K.Seidelmann, IAU Working Group (2000) LCaMD (JPL D-32296) Lunar Model • Lunar Orbit • e=0.05490 • i=5.15° from the ecliptic • a~384,400 km ~60RE • dΩ/dt=19.35°/year (18.6 year precession period) • Moon • Obliquity=6.87° from orbit, 1.54° from ecliptic • ω=13.17635815 deg/day

  9. Lunar Model • Assumed telescope at lunar barycenter • Width of MP-BS at subsolar point:3.14RE~3° • Radius of bright subsolar “spot”: 8RE~7.5°

  10. Model for (λ,µ)=(0°,0°) ☼

  11. Model for (λ,µ)=(0°,0°)

  12. Model for (λ,µ)=(0°,0°) 10° FOV ☼

  13. Model for (λ,µ)=(0°,0°) Over entire 18.6 year cycle

  14. Model for (λ,µ)=(0°,0°) 1.57° Ecliptic Coordinates, FOV centers only

  15. Model for (λ,µ)=(0°,0°) Ecliptic Coordinates, full FOV

  16. Model for (λ,µ)=(0°,0°) Galactic Coordinates, FOV centers only Subsolar point appears uniformly along band

  17. Model for (λ,µ)=(0°,0°) Galactic Coordinates, entire FOV

  18. Selenographic Longitude Selenographic Latitude

  19. “Conclusions” |µ|≥10° removes the paths of both the sun and earth from the FOV “Spot” remains in the FOV MP-BS line on the edge of field Tolerances are fairly tight! Need sun/earth constraints.

  20. Model for (λ,µ)=(10°,10°) Galactic Coordinates, entire FOV

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