James J. Bock (Chair, Caltech/JPL), Marshall W. Bautz (MIT ...
Using Reflectance Spectrometry to Identify Compositions Credit: NASA/JPL-CalTech Credit:...
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Transcript of Using Reflectance Spectrometry to Identify Compositions Credit: NASA/JPL-CalTech Credit:...
![Page 1: Using Reflectance Spectrometry to Identify Compositions Credit: NASA/JPL-CalTech Credit: NASA/JPL-CalTech/LANL.](https://reader036.fdocuments.us/reader036/viewer/2022062409/56649f175503460f94c2e84d/html5/thumbnails/1.jpg)
Using Reflectance Spectrometry to Identify Compositions
Credit: NASA/JPL-CalTech
Credit: NASA/JPL-CalTech/LANL
![Page 2: Using Reflectance Spectrometry to Identify Compositions Credit: NASA/JPL-CalTech Credit: NASA/JPL-CalTech/LANL.](https://reader036.fdocuments.us/reader036/viewer/2022062409/56649f175503460f94c2e84d/html5/thumbnails/2.jpg)
How Do We See Mars?
Our eyes, cameras, and mission instruments use the sunlight reflected off its surface.
![Page 3: Using Reflectance Spectrometry to Identify Compositions Credit: NASA/JPL-CalTech Credit: NASA/JPL-CalTech/LANL.](https://reader036.fdocuments.us/reader036/viewer/2022062409/56649f175503460f94c2e84d/html5/thumbnails/3.jpg)
Spectra Are “Fingerprints”
Fingerprints can be used to identify individual people
Credit: http://math-blog.com Credit: http://www.vetmed.vt.eduCredit: http://www.moillusions.com
![Page 4: Using Reflectance Spectrometry to Identify Compositions Credit: NASA/JPL-CalTech Credit: NASA/JPL-CalTech/LANL.](https://reader036.fdocuments.us/reader036/viewer/2022062409/56649f175503460f94c2e84d/html5/thumbnails/4.jpg)
Spectra Are “Fingerprints”
Spectra are unique to elements and minerals
Used to identify minerals; rocks
Credit: Univ. of Toronto
Credit: ChemCam/LANL/IRAP/CNES
![Page 5: Using Reflectance Spectrometry to Identify Compositions Credit: NASA/JPL-CalTech Credit: NASA/JPL-CalTech/LANL.](https://reader036.fdocuments.us/reader036/viewer/2022062409/56649f175503460f94c2e84d/html5/thumbnails/5.jpg)
Types of Spectra
Credit: http://csep10.phys.utk.edu/astr162/lect/light/spectra2.gif
![Page 6: Using Reflectance Spectrometry to Identify Compositions Credit: NASA/JPL-CalTech Credit: NASA/JPL-CalTech/LANL.](https://reader036.fdocuments.us/reader036/viewer/2022062409/56649f175503460f94c2e84d/html5/thumbnails/6.jpg)
Using the ALTA to take a Spectrum
These rocks are “Mars” rocks that you—like a rover on a mission—are analyzing. Your task it to determine their possible compositions, by comparing the Mars rocks’ spectra to known Earth rocks’ spectra.
Credit: Ward’s Scientific
![Page 7: Using Reflectance Spectrometry to Identify Compositions Credit: NASA/JPL-CalTech Credit: NASA/JPL-CalTech/LANL.](https://reader036.fdocuments.us/reader036/viewer/2022062409/56649f175503460f94c2e84d/html5/thumbnails/7.jpg)
Using the ALTA to take a Spectrum
These rocks are “Mars” rocks that you—like a rover on a mission—are analyzing. Your task it to determine its possible composition, by comparing the Mars rocks’ spectra to known Earth rocks’ spectra.
Buttons on front, LEDs & detector on the back
Push each button on the front and see what happens on the back
![Page 8: Using Reflectance Spectrometry to Identify Compositions Credit: NASA/JPL-CalTech Credit: NASA/JPL-CalTech/LANL.](https://reader036.fdocuments.us/reader036/viewer/2022062409/56649f175503460f94c2e84d/html5/thumbnails/8.jpg)
Using the ALTA to take a Spectrum
What is the ALTA doing?
Light from diode strikes the surface of the sample
Light reflected off the sample enters the detector
Read-out on the front indicates how much of the light has been reflected (voltage)
Because each ALTA has its own sensitivities, the read-out should be compared to the reflectance of white paper
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Taking the Dark Voltage
What happens if you place the ALTA down flat and don’t turn on any of the lights?
You still have a number - ALTA’s photodetector and electronics don’t go to zero. This is your “Dark Voltage”
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Using the ALTA to take a Spectrum
Need a large flat surface if possible.
Try not to let outside light into the detector.
Work in groups of 4; one can hold the sample and ALTA, one can press the buttons, one to record the data, etc.
Begin with taking the data for two stacked pieces of white paper.
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Terrestrial Spectrum #1
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Terrestrial Spectrum #2
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Terrestrial Spectrum #3
![Page 14: Using Reflectance Spectrometry to Identify Compositions Credit: NASA/JPL-CalTech Credit: NASA/JPL-CalTech/LANL.](https://reader036.fdocuments.us/reader036/viewer/2022062409/56649f175503460f94c2e84d/html5/thumbnails/14.jpg)
Terrestrial Spectrum #4
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Terrestrial Spectrum #5
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Terrestrial Spectrum #6