Spectroscopy: The Study of Squiggly...
Transcript of Spectroscopy: The Study of Squiggly...
![Page 1: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/1.jpg)
Spectroscopy: The Study of Squiggly Lines
Reflectance spectroscopy: light absorbed at specific wavelengths corresponding to energy level transi8ons
![Page 2: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/2.jpg)
Ice – liquid transi0on for water
Low water content
High water content
Phase affects spectra
Bands don’t broaden much as ice turns to water Band centers shift subtly Amount of absorption increases with optical length z in Beer’s law (e-kz) – there are no grain interfaces in water. This is a particle size effect
![Page 3: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/3.jpg)
Particle size affects spectra
Coarse par)cles – spectra dominated by absorp)on inside grains
Fine par)cles – spectra dominated by surface reflec)on
Low surface/volume ra)o Average op)cal path is long
High surface/volume ra)o
Path is shorter
![Page 4: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/4.jpg)
Particle size affects spectra
H2O Pyroxene
XY(Si,Al)2O6
![Page 5: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/5.jpg)
…and not always in a simple way
![Page 6: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/6.jpg)
Spatial resolution also affects spectra (by mixing)
Areal (checkerboard) mixing: additive Intimate mixing: non-linear
KAl(SO4)2�12H2O KFe+33(OH)6(SO4)2
![Page 7: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/7.jpg)
In0mate mixing can be highly non-‐linear
Adding highly absorptive charcoal greatly reduces the optical path length (“z” in Beer’s Law: e-kz) A small amount has a large effect Larger amounts have diminishing effect
![Page 8: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/8.jpg)
Space weathering
Nanophase iron reddens, darkens, weakens absorption bands
![Page 9: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/9.jpg)
Spectral resolu0on: mul0spectral remote sensing vs. imaging spectroscopy
Imaging spectroscopy is more likely to resolve absorp8on bands
KAl(SO4)2!12H2O
![Page 10: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/10.jpg)
The challenge of mul0spectral data
Many dis)nct minerals look similar!
![Page 11: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/11.jpg)
Dispersion Elements: Transmission Filters
![Page 12: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/12.jpg)
Dispersion Elements: Dichroic Mirrors
![Page 13: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/13.jpg)
Dispersion Elements: Prisms and Diffraction Gratings
![Page 14: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/14.jpg)
Imaging Spectrometers
![Page 15: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/15.jpg)
Let’s start with how humans sense color:
Cone-‐shaped cells within the eye absorb light in 3 wavelength ranges – RGB
They send signals to the brain propor)onal to how much light is absorbed
The brain turns these signals into the sensa)on of color
Color has three aIributes – hue, satura)on, and intensity or lightness
color (percep8on) is related to radiance (physical flux)
Sec)on of the eye
![Page 16: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/16.jpg)
DAY Bright light
NIGHT Dim light Rods are more sensi0ve than cones
In bright light, the three sets of cones send strong signals to the brain that drown out the signal from the rods. The signals are interpreted as the sensa)on of color In dim light, the signal from the single set of rods is dominant. It is interpreted as the sensa)on of black/white (gray)
![Page 17: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/17.jpg)
Addi0ve Color
![Page 18: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/18.jpg)
Addi0ve Color
Blue Green Red Blue Green Red
+
Blue Green Red
=
Blue Green Red
![Page 19: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/19.jpg)
We can describe color in different data “spaces”, e.g.: *Perceptual data space
– how we sense color intui)vely (Hue, satura)on, intensity) *Radiance data space
– how the color s)mulus is described by the measured image data
![Page 20: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/20.jpg)
HUE
SATURATION
INTENSITY (LIGHTNESS)
1) A simple perceptual color space (HSI)
![Page 21: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/21.jpg)
2) RGB radiance space
0
R
B
G
r
g
b
r=R/(R+G+B) g=G/(R+G+B) b=B/(R+G+B)
![Page 22: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/22.jpg)
McEwen et al. (JGR, 2007)
1) Use filters sequen)ally via spacecrab mo)on or filter wheel
![Page 23: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/23.jpg)
2) Use filters simultaneously
“Bayer paIern”
![Page 24: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/24.jpg)
Bayer paIern user: Curiosity’s Mars Hand Lens Imager (MAHLI)
![Page 25: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/25.jpg)
Curiosity’s Mastcam: Bayer paIern and filter wheel
![Page 26: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/26.jpg)
![Page 27: Spectroscopy: The Study of Squiggly Lineswray.eas.gatech.edu/remotesensing2015/LectureNotes/RS... · 2015. 9. 30. · Spectroscopy: The Study of Squiggly Lines Reflectance(spectroscopy:(lightabsorbed(atspecificwavelengths(corresponding(to(energy(level(transi8ons](https://reader036.fdocuments.us/reader036/viewer/2022071421/611a91e9ab1ee2775d334ed8/html5/thumbnails/27.jpg)
ASTER on board Terra: closely spaced SWIR filters to discriminate OH-‐bearing
minerals