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 R E /R) 3 cm -3 X-ray Emission proportional to –N(r)ρ(r,θ)[v(r,θ) 2 +3k B T(r,θ)/m] ½

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

5. 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 Model FOV as f(t) Given (λ,µ)

6. Lunar Model Lunar Orbit –e=0.05490 –i=5.15° from the ecliptic –a~384,400 km ~60R E –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. Lunar Model Lunar Orbit –e=0.05490 –i=5.15° from the ecliptic –a~384,400 km ~60R E –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 JPL DE405 ephemeris IDL implementation by Markwardt P.K.Seidelmann, IAU Working Group (2000) LCaMD (JPL D-32296)

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

11. Model for (λ,µ)=(0°,0°) ☼

13. ☼ 10° FOV

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

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

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

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

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

19. Selenographic Latitude Selenographic Longitude

20. “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.

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