robin fergason philip christensen msl landing site selection workshop may 31, 2006
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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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
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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
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Exposed Bedrock
800260
67.6 E
Nili Patera
66.9 E8.7 N
9.5 N
Ares Valles
Rog
ers
et a
l., 2
005
Chr
iste
nsen
et a
l., 2
003a
; 200
5
950190
341.6 E341.3 E5.9 N
6.4 N
3.4 km 3.5 km
THEMIS-derived thermal inertia overlain onto THEMIS visible
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Hebes Chasma Interior Layered Deposits
V10052001
800 m
TI: 190-245
TI: 275-360
TI: 290-420
TI: 125-145
125 615
Fergason et al., submitted
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Thermal Inertia Background
• I = (ρkc)1/2
ρ – bulk density
k – conductivity
c – specific heat
• Thermal inertia measures a material’s resistance to change in temperature
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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
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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
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Comparison with TES
25 600
180 E40 S
40 N
180 E180 E40 S
40 N
180 E
THEMIS
TES
Fergason et al., submitted
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Comparison of Mini-TES and
THEMISThermal Inertia
Fergason et al., 2006
250 430
THEMIS and Mini-TES Thermal Inertia
0
500
1000
1500
0 10 20 30 40 50 60 70 80
Spirit - Gusev Landing Site Number
Th
erm
al In
erti
a
Mini-TES Thermal Inertia THEMIS Thermal Inertia
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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
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Opportunity THEMIS Temperature Mosaic - 2003
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Opportunity THEMIS Temperature Mosaic - 2006
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63.2 E
570175
26.8 N
26.3 N62.6 E
Fergason et al., submitted
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THEMIS Day and Night IR
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Predicting Surface Temperature
1. Thermal inertia is derived from THEMIS image
2. 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
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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
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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