Lecture 7

geo.orst.edu

Lecture 7

Multispectral and Hyperspectral

Sensors

21 April 2003


Outline

• Multi-spectral remote sensing

– Landsat MSS, TM, and ETM+

– AVHRR

– MODIS

– ASTER

• Hyperspectral remote sensing

– Hyperion


Landsat Series

• Landsat 1: Multi-spectral Scanner (MSS)

• Launched in 1972

• Whiskbroom scanner

• Swath width (FOV) of 185 km

• Near polar-orbit (98.9 o degree inclination)


7-bit quantization

(2 7 DN values)


Landsat MSS Bands and their Uses

• Band 4 (0.5 - 0.6 mm)

– water features (large penetration depths)

– sensitivity to turbidity (suspended sediments)

– sensitivity to atmospheric haze (lack of tonal contrast)

• Band 5 (0.6 - 0.7 mm)

– chlorophyll absorption region

– good contrast between vegetated and non-veg. areas

– haze penetration better than Band 4

• Band 6 (0.7 - 0.8 mm) and Band 7 (0.8 - 1.1 mm)

– similar for most surface features

– good contrast between land and water (water is strong

absorber in near IR)

– both bands excellent haze penetration

– Band 7 good for discrimination of snow and ice


•8-bit quantization (2 8 DN values)


Landsat Thematic Mapper Bands and their Uses

• Band 1 (0.45 - 0.52 mm)

– good water penetration (bathymetry and coastal studies)

– differentiating soil and rock surfaces from veg. (detection of

cultural features)

– smoke plumes

– most sensitive to atmospheric haze

• Band 2 (0.52 - 0.60 mm)

– water turbidity differences

– sediment and pollution plumes

– discrimination of broad classes of vegetation

• Band 3 (0.63 - 0.9 mm)

– strong chlorophyll absorption (veg. vs. soil)

– urban vs. rural areas


Landsat Thematic Mapper Bands and their Uses

• Band 4 (0.76 - 0.90 mm)

– different vegetation varieties and conditions

– dry vs. moist soil

– coastal wetland, swamps, flooded areas

• Band 5 (1.55 - 1.75 mm)

– leaf-tissue water content ( refl. as water content )

– moisture content of soil

– snow vs cloud discrimination

• Band 6 (10.4 - 12.5 mm)

– heat mapping applications

– radiant surface temperature range: -100 o C to +150 o C

• Band 7 (2.08 - 2.35 mm)

– absorption band by hydrous mineral (clay, mica)

– lithologic mapping (clay zones)


•8-bit quantization (2 8 DN values)

•on-board calibration


Landsat Data Availability

• All data available through EROS Data Center

(EDC); partnership w/USGS

• Data acquisitions are scheduled (not

continuous)

• Prices:

– ETM+ $600/scene ($250 each additional scene)

– TM $425/scene ($200 each additional scene)

– MSS $200/scene ($100 each additional scene)


NOAA AVHRR Satellites

• AVHRR = Advanced Very High Resolution

Radiometer

• Designed for hydrological, oceanographic and

meteorological studies

• 1970 to present (longest time series)

• Coarse resolution (1.1 km at nadir)

• Global coverage (FOV = 2700 km)

• Near-polar orbit (98.9o inclination)

• Sun synchronous

• 10-bit quantization

• Real-time direct readout of data is possible


AVHRR Swath


Moderate Resolution Imaging

Spectroradiometer (MODIS)

• On-board NASA Terra and Aqua satellites

• Whiskbroom scanner

• Near-polar orbit (98 o inclination)

• Sun synchronous orbit

• FOV = 2330km

• Descending equatorial crossing time 10:30AM for

Terra, 1:30PM for Aqua

• 12-bit quantization (2 12 DN values)

• 20 spectral bands in visible and near-infrared

• 16 spectral bands in middle IR and thermal IR


Band

Bandwidth

(nm)

Pixel Size at

Nadir

Primary Use

1

2

620-670

841-876

250m


Vegetation indices

Land/cloud/aerosol boundaries

3

4

5

459-479

545-565

1230-1250

500m



Land (veg indices, land cover/land use

change, snowcover mapping, etc.), cloud

and aerosol properties

6

1628-1652


7

2105-2155


8

405-420

1000m

Ocean color/phytoplankton/biogeochemistry

9

438-448


10

483-493


11

526-536


12

546-556


13

662-672


14

673-683


15

743-753


16

862-877


17

890-920


Atmospheric water vapor

18

931-941


19

915-965


MODIS ocean

color:

Coccolithophores

in the Gulf of

Maine


MODIS image of Biscuit Fire

12 August 2002


Advanced Spaceborne Thermal Emission

and Reflection Radiometer

• On-board Terra satellite

• Consists of 3 different subsystems:

– Visible/Near-infrared, Shortwave IR, Thermal IR

• VNIR has stereo capability (DEM creation)

• Swath width of 60km

• 8-bit quantization, adjustable gain

• Pointable

• Data acquisition is scheduled


Characteristic

VNIR

SWIR

TIR

Spectral

Range

Band 1: 0.52 - 0.60 mm

Nadir looking

Band 4: 1.600 -

1.700 mm

Band 10: 8.125 -

8.475 mm

Band 2: 0.63 - 0.69 mm

Nadir looking

Band 5: 2.145 -

2.185 mm

Band 11: 8.475 -

8.825 mm

Band 3: 0.76 - 0.86 mm

Nadir looking

Band 6: 2.185 -

2.225 mm

Band 12: 8.925 -

9.275 mm

Band 3: 0.76 - 0.86 mm

Backward looking

Band 7: 2.235 -

2.285 mm

Band 13: 10.25 -

10.95 mm

Band 8: 2.295 -

2.365 mm

Band 14: 10.95 -

11.65 mm

Band 9: 2.360 -

2.430 mm

Pixel size at

nadir

15m

30m

90m

Cross-track

pointing (deg)

±24

±8.55

±8.55

Cross-track

pointing (km)

±318

±116

±116


ASTER-derived DEM, 30m

ASTER truecolor image, 15m

Thompson Glacier on Axel Heiberg

Island, Canada


Multispectral vs. Hyperspectral

Remote Sensing

Multispectral

• separated spectral

bands

• wider bandwidths

• coarse representation

of the spectral signature

• smaller image size

Hyperspectral

• no gaps

• narrow bandwidths

(10nm)

• complete representation

of the spectral signature

• ability to detect subtle

spectral features

• large image size

• radiometric and spectral

calibration are timeconsuming


Hyperion: Imaging Spectrometer

• On-board NASA EO-1 satellite (demonstrating new

sensor technologies)

• Pushbroom sensor at 705 km altitude (7.6 km swath

width)

• Sun synchronous orbit

• Near-polar orbit (98 o inclination)

• Flying in formation w/Landsat 7 (1 min)

• spectral range 0.43 - 2.4 mm, 10 nm bandwidths

• 220 spectral bands (uses diffraction grating to disperse

light into separate wavelengths and project onto CCD

array and HgCdTe detectors)

• 30m spatial resolution

• 12-bit quantization

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