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Robin Fergason Philip Christensen MSL Landing Site Selection Workshop May 31, 2006

Determining surface characteristics at candidate MSL landing sites using THEMIS high-resolution orbital thermal inertia data. Robin Fergason Philip Christensen MSL Landing Site Selection Workshop May 31, 2006. Thermal Inertia Background. Used to infer a particle size of the surface layer

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Robin Fergason Philip Christensen MSL Landing Site Selection Workshop May 31, 2006

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  1. Determining surface characteristics at candidate MSL landing sites using THEMIS high-resolution orbital thermal inertia data Robin Fergason Philip Christensen MSL Landing Site Selection Workshop May 31, 2006

  2. Thermal Inertia Background • Used to infer a particle size of the surface layer • Helps to identify features, their location and extent on the surface, and their particle size • Detect exposed bedrock and dust

  3. Ares Valles Exposed Bedrock 6.4 N Nili Patera 9.5 N Christensen et al., 2003a; 2005 Rogers et al., 2005 3.4 km 3.5 km 5.9 N 8.7 N 66.9 E 67.6 E 341.3 E 341.6 E 800 260 950 190 THEMIS-derived thermal inertia overlain onto THEMIS visible

  4. Hebes Chasma Interior Layered Deposits TI: 125-145 TI: 190-245 TI: 275-360 TI: 290-420 125 615 800 m Fergason et al., submitted V10052001

  5. I = (ρkc)1/2 ρ – bulk density k – conductivity c – specific heat Thermal inertia measures a material’s resistance to change in temperature Thermal Inertia Background

  6. THEMIS-derived thermal inertia • Use thermal model developed by H. H. Kieffer • Ls, latitude, local time from spacecraft ephemeris • TES-derived albedo (8ppd) • MOLA-derived elevations (128 epd) • TES-derived dust opacity (2 ppd) every 30° Ls • Radiance at 12.57 μm (Band 9) is converted to brightness temperature, correcting for drift and wobble of the spacecraft • Interpolate upon a 7-D look-up table

  7. THEMIS-derived Thermal Inertia Uncertainties • Uncertainties are primarily due to: (1) instrument calibration (2) uncertainties in model input parameters (3) thermal model uncertainties • Variations in thermal inertia within a single image are accurate and represent differences in the physical properties of the surface

  8. Comparison with TES TES 40 N 40 S 180 E 180 E THEMIS 40 N 40 S 180 E 180 E Fergason et al., submitted 25 600

  9. Comparison of Mini-TES and THEMISThermal Inertia 250 430 Fergason et al., 2006

  10. Landing Site Characterization • Identify regions of very high or very low thermal inertia • TI > 400 likely has rocky surface [Nowicki, 2006] • TI < 100 is likely dusty and not drivable • Evaluate surface properties of the candidate landing sites • Predicted surface temperature for the primary mission • Rover design temperature limits: 145 - 310 K • Maximum diurnal temperature range: 145 K

  11. Opportunity THEMIS Temperature Mosaic - 2003

  12. Opportunity THEMIS Temperature Mosaic - 2006

  13. 26.8 N 26.3 N 62.6 E 63.2 E 175 570 Fergason et al., submitted

  14. THEMIS Day and Night IR

  15. Thermal inertia is derived from THEMIS image The derived thermal inertia value is then used to calculate the surface temperature for a given local time and season Can predict the minimum surface kinetic temperature during the primary mission Predicting Surface Temperature

  16. ASU Will Provide • Interpretations of THEMIS and TES thermal inertia data for all candidate landing sites • Thermal inertia mosaics of candidate landing site regions (100 m) • Relative thermal inertia values

  17. ASU Will Provide • Individual thermal inertia images of specific areas of interest (100 m) • Thermal inertia values of specific morphologies • Predicted temperature maps of candidate landing site regions (100 m) • Predict range of temperatures • Derive maximum diurnal temperature range

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