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Wednesday, 2 February 2011. Lecture 9: Spectroscopy. Reading. Ch 5.14 Ch 6.1-3 Ch 4.5 . What was covered in the previous lecture. 1) reflection/refraction of light from surfaces (surface interactions) Last Friday’s lecture: 2) volume interactions - resonance

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slide1

Wednesday, 2 February 2011

Lecture 9: Spectroscopy

Reading

Ch 5.14

Ch 6.1-3

Ch 4.5

slide2

What was covered in the previous lecture

  • 1) reflection/refraction of light from surfaces
  • (surface interactions)
  • Last Friday’s lecture:
  • 2) volume interactions
  • - resonance
  • - electronic interactions
  • - vibrational interactions
  • Today’s lecture
  • 3) spectroscopy
  • - continuum vs. resonance bands
  • - spectral “mining”
  • - continuum analysis
  • and
  • 4) spectra of common Earth-surface materials

LECTURES

Jan 05 1. Intro

Jan 07 2. Images

Jan 12 3. Photointerpretation

Jan 14 4. Color theory

Jan 19 5. Radiative transfer

Jan 21 6. Atmospheric scattering

  • Jan 26 7. Lambert’s Law previous
  • Jan 28 8. Volume interactions today

Feb 02 9. Spectroscopy

Feb 04 10. Satellites & Review

Feb 09 11. Midterm

Feb 11 12. Image processing

Feb 16 13. Spectral mixture analysis

Feb 18 14. Classification

Feb 23 15. Radar & Lidar

Feb 25 16. Thermal infrared

Mar 02 17. Mars spectroscopy (Matt Smith)

Mar 04 18. Forest remote sensing (Van Kane)

Mar 09 19. Thermal modeling (Iryna Danilina)

Mar 11 20. Review

Mar 16 21. Final Exam

2

slide3

Discussion:

1) reflection/refraction of light from surfaces

(surface interactions)

2) volume interactions

- resonance

- electronic interactions

- vibrational interactions

3) spectroscopy

- continuum vs. resonance bands

- spectral “mining”

- continuum analysis

4) spectra of common Earth-surface materials

slide4

Spectra vary

with composition

Minerals

Ices

CaCO3

MgCO3

Be3Al2(SiO3)6

CaSO42(H2O)

KAl(SO4)212H2O

KFe+33(OH)6(SO4)2

slide5

Fig 2.21, Siegal & Gillespie

For silica in TIR

Molecular vibration modes in silicates affect the thermal infrared

Thermal infrared

silicates

slide6

Reflectance spectrum of SiO2 in the TIR

QUARTZ: SiO2

The doubled peak is due to crystallographic asymmetry (hexagonal) in quartz

The silica tetrahedron is distorted in quartz: the Si-O bond

down the c-axis has a different length than it does across it

slide7

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 affect

Low water content

Ice – liquid

transition

for water

High water

content

slide8

Particle size affects spectra

Fine particles – spectra

dominated by surface reflection

Coarse particles – spectra

dominated by absorption inside grains

High surface/volume ratio

Path is shorter

Low surface/volume ratio

Average optical path is long

slide10

Particle size affects spectra

Pyroxene

H2O

XY(Si,Al)2O6

slide11

Spectral resolution:

multispectral

remote sensing vs. imaging spectroscopy

KAl(SO4)212H2O

Imaging spectroscopy is more likely to resolve absorption bands

slide12

Spatial resolution also affects spectra (by mixing)

KFe+33(OH)6(SO4)2

KAl(SO4)212H2O

Areal (checkerboard) mixing: additive

Intimate mixing: “subtractive”

slide13

Intimate 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

slide14

Spectroscopy

considerations

- continuum vs. resonance bands

Absorption bands are measured relative to the “continuum” – the value of the spectrum if the absorption band was not present

slide15

Discussion:

1) reflection/refraction of light from surfaces

(surface interactions)

2) volume interactions

- resonance

- electronic interactions

- vibrational interactions

3) spectroscopy

- continuum vs. resonance bands

- spectral “mining”

- continuum analysis

4) spectra of common Earth-surface materials

slide16

SOIL

Path length

Clay

H2O

Fe-O

Water absorption

Spectra of common Earth-surface materials

slide17

Green

Vegetation

Water absorption

Chlorophyll absorption

Cellular scattering

Spectra of common Earth-surface materials

slide18

Dry

Vegetation

Cellulose

Water absorption

Cellular scattering

Spectra of common Earth-surface materials

Chlorophyll absorption

slide19

Leaf structure and its relation to spectra

Absorption band in red: chlorophyll pigment

Reflective NIR: scattering in the prismatic leaf cells

SWIR absorption: absorption by leaf water

slide20

Next Class:

  • Satellites & orbits
  • Review for Midterm