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Earth, Planets and Space
Fig. 5 | Earth, Planets and Space

Fig. 5

From: Miniature lightweight X-ray optics (MiXO) for surface elemental composition mapping of asteroids and comets

Fig. 5

Comparison of minimum detection time (global, non-imaging) of XRF in 0.5–2 keV (depending on the optical/IR filtering scheme, mirror reflectivity and other optics onfiguration) as a function of distance to the target for NEAR-Shoemaker (green), Hayabusa (red) and MiXO (blue) with planned orbital profiles (OSIRIS-REx, yellow). The orbit radius and standoff distance are rescaled to the target size. Collimator instruments become useless beyond a certain distance due to high cosmic X-ray background, whereas focusing optics can extend the useful observing condition to a much wider range of orbit profiles, allowing a flexible mission design. The minimum detection time is the total exposure that is required to acquire the signal-to-noise ratio above a certain limit (e.g. \(5\sigma\))

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