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M.A.D.A.N.A.C M easurement A nd D iscovery of A steroids and N EOs in A ntarcti C a

M.A.D.A.N.A.C M easurement A nd D iscovery of A steroids and N EOs in A ntarcti C a. Physical characterization is losing the race against discovery. (Data from Tedesco, private communication ). Near-Earth Objects: What We Would Like To Know Better. Inventory and Size Distribution

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M.A.D.A.N.A.C M easurement A nd D iscovery of A steroids and N EOs in A ntarcti C a

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  1. M.A.D.A.N.A.C Measurement And Discovery of Asteroids and NEOs in AntarctiCa

  2. Physical characterization is losing the race against discovery (Data from Tedesco, private communication)

  3. Near-Earth Objects: What We Would Like To Know Better • Inventory and Size Distribution • Asteroidal/Cometary Contribution • Origin, History and Evolution • Composition • Internal Structure: Density, Impact Strength, MacroscopicPorosity • Regolith Properties • Spin rates • Binarity

  4. In situ Exploration • In situ Exploration • Remote Observations • Remote Observations • Remote Observations How to improve our knowledge on: • Statement from the conclusions of the Erice Space Chemistry School, July 2001 on “The Physical Properties of Potential Earth Impactors: Know Your Enemy” • The most crucial datum needed for assessing the NEO hazard is the size of the objects. This information is lacking for the majority of known NEOs and is the highest measurement priority after discovery and orbit determination. • Masses and densities? • Internal structures? • How many? • Size and albedo distribution? • Taxonomic distribution?

  5. PHOTOMETRY

  6. Thermal Radiometry NEOs are bright in the thermal IR ! Asteroids emit both scattered sunlight at visible wavelengths, and thermal radiation in the IR. Simultaneous measurement of V and thermal IR fluxes lead to determination of albedo and size. (Courtesy of S. Price)

  7. THE (923) HERLUGA FIELD IN THE VISIBLE AND IR (MSX Observations) (Courtesy of S. Price)

  8. For D = 1 km and pV= 0.16 Microns 12 8.5 4.7 0.55 (Computations by E.F. Tedesco)

  9. 1 UA Diameter in Km as a function of albedo (visible))

  10. (data from E.F. Tedesco)

  11. Radiometry allows to obtain sizes and albedos • Objects are bright at mid-IR wavelengths • Stellar background substantially reduced, even at low galactic latitudes • Modest dependence of IR luminosity on phase angle Jon Lawrence and Michael Burton Advantages of mid-IR observationsof NEOs • Radiometry allows to obtain sizes and albedos • Objects are bright at mid-IR wavelengths • Stellar background substantially reduced, even at low galactic latitudes • Modest dependence of IR luminosity on phase angle … but from the ground, in recent years, no more than 10 NEOs per year on the average have been observed in the thermal IR. Most of the available IR data have been obtained so far by space missions (IRAS, MSX)

  12. POLARIMETRY

  13. Polarimetry This technique is based on some empirical relationships between the degree of linear polarization (measured through the Stokes parameters Q and U) and the surface albedo. What is usually measured is the parameter: Pr = ( I- I) / ( I + I//) Where I and I are the intensities of the components linearly polarized along the directions perpendicular and parallel to the scattering plane, respectively.

  14. Polarization curve of 1 Ceres

  15. The slope – albedo relationship (from Dollfus et al., 1989)

  16. Polarimetry in IR : never done at this moment Inputs to models A new way to classify taxonomy ?

  17. SPECTROSCOPY

  18. Asteroid Taxonomic Classes (from Tholen and Barucci, 1989)

  19. a): Ni-Fe b): Olivine c): Ortopyroxene d): Feldspar e): Spinel

  20. IR spectroscopy (or color-photometry) allows to discriminate taxonomic types

  21. DETECTION

  22. Aten objects: a < 1, Q > 0.983 AU Solar elongations vs. Earth distance Orbital evolution of 21 Atens (821 yrs). Solar elongations vs. Earth distance every 40 days. Large dots: Mv < 16 Medium dots: 16 < Mv < 18 Small dots: 18 < Mv < 20 (integrations made by Boattini and Carusi)

  23. IEOs: a class of NEOs totally interior to the Earth’s orbit In addition to Atens, a new class of objects, with orbits completely inside Earth’s orbit, have been found to exist necessarily, through numerical integrations of NEO orbitsperformed in 2000. These objects have been called IEOs (objects Interior to Earth’s Orbit). Where on earth can we make observations in direction of the sun …? These objects are extremely hard to discover, due to the difficulty of observing them from ground, since they never are visible at large solar elongations.The first IEO discovery has been made by LINEAR not earlierthan 2003.

  24. There are things to do at Dome C for asteroids: Discoveries : NEOs, IEOS but also MBAs and TNOs Measurements: albedo, size, taxonomy: photometry, spectroscopy, polarimetry Great benefits of IR M.A.D.A.N.A.C could (should ?) exist….

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