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Lect8 Radiometry (10-15-09) - Radiometry of Asteroids and...

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Radiometry of Asteroids and Comets (continued) October 15, 2009
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OUTLINE I. Introduction: Thermal Emission and Reflected Light II. Standard Thermal Model (STM) III. Deviations from the STM: Fast-rotating (ILM) Thermophysical Model NEATM Non-sphericity I. A Few Examples: 1 Ceres NEAs Comets Centaur 2060 Chiron I. Future Observations
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II. Standard Thermal Model The Factor η For a smooth, non-rotating body, η is defined as 1.0. Surface roughness tends to decrease η by enhancing sunward emission, and Rotation of a body with non-zero thermal inertia increases η . Two slides ago the STM assumes η = 0.756, what does that mean in terms of temperature compared with η = 1.0. What about rotation and roughness? .
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III. Deviations from the STM A. Fast-rotating, Thermophysical, and NEATM Models 1. Fast-rotating (a.k.a. rocky): figure 4 . Isothermal Latitude Model (ILM)
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III. Deviations from the STM A. Fast-rotating, Thermophysical, and NEATM Models 1. Fast-rotating (aka rocky): figure 4 2. Thermophysical: range of parameters between STM and fast-rotating. Can handle non-spherical objects. Needs shape and pole orientation as input. 3. NEATM, variation of the STM to account for NEAs observed at larger range of phase angles and thermal properties different from large Main-Belt asteroids . Requires observations at least at two thermal wavelengths to determine color temperature. .
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III. Deviations from the STM A. Non-sphericity Departures from sphericity of up to 30% do not have a significant impact on the calculated radius and albedo. However, greater departures have to be incorporated into models (R. H. Brown 1984). .
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III. Deviations from the STM A. Cometary Activity So far several “low activity” comets have been modeled successfully using the STM and the ILM models.
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