Imaging spectrometry at visible and infrared wavelengths using
MARS ODYSSEY October 24, 2001. Thermal Emission Imaging System (THEMIS) Visible Imaging System...
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Transcript of MARS ODYSSEY October 24, 2001. Thermal Emission Imaging System (THEMIS) Visible Imaging System...
Thermal Emission Imaging System (THEMIS)
• Visible Imaging System
– Visible-light images with 18 meters per pixel resolution
• Infrared Imaging System
– Infrared data set with 100 meters per pixel resolution
THEMIS Visible Image
Context Image:
MOLA Shaded Relief
-19N, 173E
THEMIS THEMIS visible imagesvisible images are taken during are taken during the afternoon the afternoon and the sun is and the sun is shining from the shining from the leftleft
Most THEMIS visible imagesMost THEMIS visible imagesare ~18 km acrossare ~18 km across
CONTEXT CONTEXT imagesimages appear to appear to have the sun have the sun shining from shining from the rightthe right
2N, 237E2N, 237E
THEMIS Visible Image: Caldera
Context Image
Landslide closeups
THEMIS visible images
Melas Melas ChasmaChasma-9N, 282E-9N, 282E
Ius Chasma-7N, 275E
THEMIS Visible Image: Splosh
Crater with central peak and slumps
Context Image
55N, 190E
Central Peak
Slumps
22N, 126E22N, 126E
THEMIS Visible Image
Context Image
22N, 126E22N, 126E
THEMIS Visible Image: Channel
Context Image
Behavior of Light– Reflect– Transmit– Absorb– Emit
• In the visible, we are seeing reflected light
• In the infrared, we are detecting emitted energy
Infrared Energy/Light
• Primarily thought of as heat (thermal radiation) • Is part of the EM spectrum• Infrared energy is just beyond the red portion of
the visible light spectrum – we can not see infrared energy with our eyes
• Any object that has a temperature above absolute zero (~-273C or ~-460F) radiates in the infrared
• Just about everything emits energy in the infrared – Everything glows!
Heating Effects
• Sunlight versus shadow• Black versus white (Albedo)
– What would you rather stand on:• Black asphalt parking lot• White concrete sidewalk
– Albedo: A measure of how much light is being reflected
• Dark colored material: reflects little light, absorbs a lot of light = low albedo
• Light colored material: reflects a lot of light, absorbs little light = high albedo
Shadow Mapping Activity: Shadow and Sun Effects
Materials Needed:
-Notebook
-IR Thermometers
-Pencil
-Colored pencils
Shadow Mapping Activity: Shadow and Sun Effects
1. Find an object which is casting a large shadow and will be in the sunlight for most of the day.
2. Record the current time, and sketch (as seen from above) the shadow cast by the object. Be sure to indicate which way is north on sketch.
3. Using the IR thermometer, measure the temperature of the object and the surrounding ground at the points indicated in the sample drawing.
4. Create a temperature scale and color your temperature map.
Temperature in Black and White Activity: Albedo Effects
Materials Needed:
-Notebook
-IR Thermometers
-Black and white albedo samples
-Stopwatch
-Colored pencils
Heating Effects
Heating Effect Visible Day IR Night IRSunlight High Bright Hot N/E
Low Dark Cold N/E
Albedo High Bright Cold N/E
Low Dark Hot N/E
TI High
Low
Thermal Inertia
• Thermal Inertia (TI) = measures the amount of energy it takes to heat up a materials and how long it takes that material to cool down after the energy source is removed
• High TI = requires more energy to heat up and cool down
• Low TI = requires less energy to heat up and cool down
Thermal Inertia
• Think of a sandy beach during the day:
As you walk around, what is really hot?
• Think of that same sandy beach at night:
What is the temperature like of the sand? How about the rocks?
What takes more energy to be heated up and cool down (loose it’s heat)? = High TI
What takes less energy to heat up and cool down (heats up and cools down more quickly)? = Low TI
Heating Effects
Heating Effect Visible Day IR Night IRSunlight High Bright Hot N/E
Low Dark Cold N/E
Albedo High Bright Cold N/E
Low Dark Hot N/E
TI High
Low