Geosynchronous Orbit

• A satellite in geosynchronous orbit circles the earth once each day.

• The time it takes for a satellite to orbit the earth is called its period.

• To stay over the same spot on earth, a geostationary satellite also has to be directly above the equator.

• Otherwise, from the earth the satellite would appear to move in a north-south line every day.

Sun-Synchronous Orbit • Because the valid comparison of

images of a given location acquired on different dates depends on the similarity of the illumination conditions, the orbital plane must also form a constant angle relative to the sun direction.

• This is achieved by ensuring that the satellite overflies any given point at the same local time, which in turn requires that the orbit be sun-synchronous

• The satellite crossed the equator at approximately the same local sun time (9:42) every day

Earth Resource Satellites Operating in the Optical Spectrum• Landsat • SPOT • Meteorological Satellites

– NOAA satellites – GOES satellites

• Ocean Monitoring Satellites – Radar Satellites – Seasat – ERS-1 – JERS-1 – Radarsat

Landsat-7

• This program is jointly managed by NASA and USGS (http://landsat.gsfc.nasa.gov/announcements/program_update.html)

• Launched on April 15, 1999 (http://landsat.gsfc.nasa.gov/main/project.html)

• A new sensor : Enhanced Thematic Mapper Plus (ETM+)

• Same swath as ETM, similar orbits and characteristics• Swath: The area imaged on the surface.

ETM+

• Resolution– Bands1-5, 7: 30 meters– Band 6 (Thermal band): 60 meters– Band 8 (Panchromatic band): 15 meters

• Complete global view four times a year

ETM+

• Ground transmission of data either directly or stored onboard for later transmission

• GPS is included for subsequent geometric processing of the data

• Primary receiving station: EROS Dara Center, SD

ETM+ Spectral Bands

Landsat 7 +ETM Spectral Bands

Band Wavelength/ µm

Spectral Location

Principal Applications

1 0.45-0.52

Blue Designed for water body penetration, making it useful for coastal water mapping. Also, useful for soil/vegetation discrimination, forest type mapping and cultural feature identification.

2 0.52-0.60

Green Designed to measure green reflectance peak of vegetation for vegetation discrimination and vigor assessment. Also useful for cultural feature identification

3 0.63-0.69

Red Designed to sense in a chlorophyll absorption region aiding in plant species differentiation. Also useful for cultural identification.

4 0.76-0.90

Near infrared

Useful for determining vegetation stress, vigor, and biomass content, for delineating water bodies, and for soil moisture discrimination.

5 1.55-1.75 Mid-infrared

Indicative of vegetation moisture content and soil moisture. Also useful for differentiation of snow from clouds.

6 10.4-12.5

Thermal infrared

Useful in vegetation stress analysis, soil moisture discrimination, and thermal mapping applications.

7 2.08-2.35 Mid-infrared

Useful for discrimination of mineral and rock types. Also sensitive to vegetation moisture content.

Landsat Resources

• Data acquisition

(http://landsat.usgs.gov/pathrows.php

Enhanced Thematic Mapper Plus (ETM+)

• 8 8-bit bands: bands 1-7 are the same as TM; additional panchromatic band 8, 0.52-0.90 μm

• IFOV 30 x 30m (bands 1-5 and 7), 60 x 60m (band 6), 15 x 15m (band 8); swath width 185 km.

• Images the earth once every 16 days; 1999 to present

EOS Terra• ASTER

– The ASTER is a cooperative effort between NASA and Japan’s Ministry of International Trade and Industry

– Primary applications include study vegetation, rock types, volcanoes, clouds, and produce DEM’s

– 6 SWIR bands: band 6 centered at the clay absorption feature and band 8 at the carbonate absorption feature

– 5 TIR bands: bands 10, 11, and 12 at sulfate and silica absorption features

ASTER Characteristics• Wide Spectral Coverage

• 3 bands in VNIR (0.52 – 0.86 μm)• 6 bands in SWIR (1.6 – 2.43 μm)• 5 bands in TIR (8.125 – 11.65 μm)

• High Spatial Resolution• 15m for VNIR bands• 30m for SWIR bands• 90m for TIR bands

• Quantization (bits)• 8 for VNIR AND SWIR • 12 for TIR

• Swath width 60 km

• Images are not acquired based on researcher scheduling

• 1999 to present

ASTER consists of 3 subsystems:VNIR, SWIR and TIR

ASTER TM

Repeat Orbit: 16 d 16 d Scene 60 km 185km

Bands:Pan 0 1 15mVIS 2 15m 3 30mNIR 1 30m 1 30m

SWIR 6 30m 2 30mTIR 5 90m 1 90m

ASTER Images of San Francisco Bay

False Color Image (VNIR)

Sediment Load (VNIR)

Water Temperature (TIR)

Land Observing Sensors and their FeaturesWeather, Global Coverage Satellites

Sensor Name Pixel Swath No. Spectral Spectral Temporal

  Resolution Width, km Bands Coverage Repeat, days

AVHRR 1.1km 2700 5 VNIR, TIR 4*day

SPOT Vegetation 1.15km 2250 4 VNIR, SWIR 26

MODIS 0.25,0.5,1km 2330 36 VNIR, SWIR, TIR 2* day

Regional Satellites

Sensor m km bands Spectral Repeat

ASTER 15, 30, 90 60 16 VNIR, SWIR, TIR 16

Landsat ETM+ 30, 60, 15 185 8 Pan + TM 16

SPOT HRV 10, 20 60 4 Pan, VNIR 26

SPOT HRVIR 10, 20 60 5 SWIR + HRV 26

Local Coverage Satellites

Sensor m km bands Spectral Repeat

Quickbird 0.61 Pan, 2.44 16.5 5 Pan, VNIR 2 to 11

IKONOS 1.0 Pan, 4 11.3 5 Pan, VNIR 3

Medium and coarse resolution sensors

Sensor Pixel Size, m

‘blue’nm

‘green’nm

‘red’nm

‘NIR’nm

‘SWIR’m

‘Thermal’m

SPOT-VEGETATIONSwath 2250 km

1150 430-470 610-680 780-890 1.58-1.75

NOAA- AVHRRSwath 2700 km

1100 570-700 710-980 3.5-3.9310.3-11.311.5-12.5

MODIS (Terra, Aqua)Swath 2330 km

250 500

1000

459-479

405-420438-448483-493

545-565

526-536546-556

620-670

662-672673-683

841-876

743-753862-877890-920915-965931-941

1.23-1.251.628-1.6522.105-2.1551.360-1.390 3.66-3.84

3.929-3.9894.02-4.084.433-4.4984.482-4.5496.535-6.8957.175-7.4758.400-8.7009.580-9.88010.78-11.2811.77-12.2713.185-13.48513.485-13.78513.785-14.08514.085-14.385

Medium and coarse resolution sensors

IkonosSwath 13 km

41 (pan)

450-520 520-600 630-690 760-900

QuickBirdSwath 16.5 km

2.440.61 (pan)

450-520 520-600 630-690 760-900

Sensor Pixel Size, m

‘blue’nm

‘green’nm

‘red’nm

‘NIR’nm

‘SWIR’m

‘Thermal’m