Remote Sensing Systems

Early Satellite Sensing• Spy satellites gave exquisite but very local

views and were classified

• Even before satellites were launched, it was clear that color imaging was essential

• Best images were from manned spacecraft– Low latitude– Limited coverage in space and time– Almost all oblique

Gemini XII, 1968

(410 miles)

Early Satellite Sensing

• Meteorological satellites gave hints of what might be possible– Snow coverage– Sea ice– Glaciers– Gross geological structures

Nimbus I image 1964

Landsat• Landsat 1 1972-1978• Landsat 2 1975-1981 • Landsat 3 1978-1983• Landsat 4 1982-1993 • Landsat 5 1984, still functioning• Landsat 6 1993, failed to reach orbit • Landsat 7 1999, still functioning, but with

faulty scan line corrector (May 2003)• Landsat Data Continuity Mission,

scheduled for 2012

Two Key Features of Landsat

• Orbits are sun synchronous: satellite crosses equator southbound on day side at about 10 AM local time

• Orbits repeat ground track precisely every 14-18 days (Revisit period)

• A term to know: Nadir = point directly below (opposite of Zenith)

Early Landsat• Originally modeled on Nimbus weather

satellite system• Landsat 1 observed in Green, Red and

two IR bands with 80-m resolution• Landsat 3 had 30-m resolution• Landsat 3 added a fifth thermal IR band

but it failed• Landsat 4: 7 bands• Landsat 7: 15 m resolution panchromatic

Failed Experiment• President Jimmy Carter recommended private

sector operation of Landsat, 1979• Earth Observation Satellite Company (EOSAT),

a partnership of Hughes Aircraft and RCA, was awarded ten year contract to operate Landsat, 1985

• EOSAT operated Landsats 4 and 5 and had exclusive rights to market Landsat data.

• EOSAT needed repeated bailouts• Congress passed Land Remote Sensing Policy

Act (Public Law 102-555) and returned Landsat to public domain, 1992

Landsat 7 Bands1 0.45-0.52µm Blue-Green 30 m

2 0.52-0.60 µm Green 30 m

3 0.63-0.69 µm Red 30 m

4 0.76-0.90 µm Near IR 30 m

5 1.55-1.75 µm Mid-IR 30 m

6 10.40-12.50 µm Thermal IR 60 m

7 2.08-2.35 µm Mid-IR 30 m

0,52-0.90 µm Panchromatic 15 m

Uses of Landsat 7 Bands

1. Coastal water mapping, soil/vegetation discrimination, forest classification, man-made feature identification

2. Vegetation discrimination and health monitoring, man-made feature identification

3. Plant species identification, man-made feature identification

4. Soil moisture monitoring, vegetation monitoring, water body discrimination

5. Vegetation moisture content monitoring6. Surface temperature, vegetation stress monitoring, soil

moisture monitoring, cloud differentiation, volcanic monitoring

7. Mineral and rock discrimination, vegetation moisture content

False Color Images

• Near IR (ETM+ band 4) Red

• Red (ETM+ band 3) Green

• Green (ETM+ band 2) Blue

• Colors on image are shifted one band toward blue compared to real scene

Making a False-Color Image

Landsat 7 Facts

• Altitude: 705 kilometers • Period: 98.9 minutes• Inclination: Sun-synchronous, 98.2 degrees• Equatorial crossing: Southbound 10:00AM +/-

15 min.• Repeat coverage interval: 16 days (233

orbits)• Swath width: 185 kilometers• On-board data storage: ~375 Gb (solid state)

See SPOT. See SPOT See

• Satellite Pour l'Observation de la Terre

• Sun-synchronous

• Altitude: 832 kilometers,

• Inclination: 98.7

• Revisit period: 26 days

• Uses CCD’s and stare mode; no scanning

SPOT 5 Bands

Band (microns) Colors Resolution

0.51 - 0.73 Panchromatic 2.5 & 5m

0.50 - 0.59 Green 10m

0.61 - 0.68 Red 10m

0.79 - 0.89 Near IR 10m

1.58 - 1.73 Mid IR 20m

SPOT Image of Kuwait City, 2004

IKONOS

• 1992 Land Remote Sensing Policy Act permitted private companies to enter the satellite imaging business.

• Lockheed Martin

• Launched 2000

• 1 m resolution

• Bands: Blue, Green, Red, Near IR

• Now operated by GeoEye Inc., Dulles VA

Burj Khalifa by IKONOS

Terra• Part of NASA EOS (Earth Observation System)• Partnership of U.S., Canada, Japan• Instruments

– ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer)

– CERES (Clouds and Earth's Radiant Energy System)– MISR (Multiangle Imaging Spectroradiometer)– MODIS (Moderate-Resolution Imaging

Spectroradiometer)– MOPITT (Measurements of Pollution in the

Troposphere)

ASTER• U.S. – Japan joint mission

• Three Subsystems, each with own telescopes

• VNIR: Four visible and near-IR channels, 15-m resolution

• SWIR: Six short wave IR channels, 30-m resolution

• TIR: Five Thermal IR Channels, 90-m resolution– IR sensors use Stirling Cycle coolers

MODIS• Resolutions 250, 500 and 1000 meters

• Ten visible bands (250 and 500-m)

• Ten Near IR bands (500 and 1000 m)

• 16 Medium and Thermal IR bands (1000 m)

• Bands are narrow and tailored to specific emissions and absorptions (ocean color, aerosols, ozone, water vapor, cloud temperature)