Envisat

Envisat launched on 1st March 2002 is the most powerful European Earth-observation satellite. Envisat is a key element of the European Space Agency's plans for the next decade to monitor Earth's environment. It carries instruments to collect information that will help scientists to understand each part of the Earth system and to predict how changes in one part will affect others (Table 8). It is in a Sun synchronous orbit at an altitude of 800 km and carrying 10 instruments onboard.

Variety of earth resources satellites are currently commercially available for inventorying and monitoring earth resources. These satellites are characterised by varying spatial, spectral, radiometric and temporal resolutions (Table 9).

Satellite Name

Launch

Sensors

Types

No. of Bands

Spectral Range (microns)

(km)

Revisit Time

IKONOS-2

September

IKONOS

Multi-spectral

4

0.45-0.52 (blue)

4

11 days

24, 1999

0.52-0.60 (green)

0.63-0.69 (red)

0.76-0.90 (NIR)

PAN

1

1

Table 8. Envisat's Instrument

(source: www.esa.int/export/esasa/ESADTOMBAMC_earth_0.html)

Instrument

Main purpose

Global ozone monitoring by occupation of stars (GOMOS)

To observe the concentration of ozone in the stratosphere.

Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY)

To measure trace gases and aerosol concentrations in the atmosphere.

Michelson interferometer for passive atmospheric sounding (MIPAS)

To collect information about chemical and physical processes in the stratosphere, such as those that will affect ozone concentration in future.

Medium resolution imaging Spectrometer (MERIS)

Measures radiation in 15 frequency bands that give information about ocean biology, marine water quality and vegetation on land, cloud and water vapor.

Advanced synthetic aperture Radar (ASAR)

All weather, day or night radar imaging.

Advanced along track scanning radiometer (AATSR)

To measure sea-surface temperature, a key parameter in determining the existence and/or extent of global warming.

Radar Altimeter (RA-2)

Measures distance from satellite to Earth. So can measure sea-surface height, an important measurement for monitoring El Nino, for example.

Microwave radiometer (MWR)

Allows corrections to be made to radar altimeter data.

Doppler Orbitography and Radio positioning integrated by satellite

(DORIS)

Gives the position of Envisat in its orbit to within a few centimeters. This is crucial to understanding the measurements all the instruments make.

Laser retro-reflector (LRR)

Reflects pulsed laser to ground stations to help determine the satellite's exact position in its orbit.

Table 9. Characteristics of some more commercially available satellites

Satellite Name

Launch

Sensors

Types

No. of Bands

Spectral Range (microns)

(km)

Revisit Time

QuickBird-2

Oct. 18, 2001

Multi-

4

blue (0.45-0.52)

2.5

17

spectral

green (0.52-0.6)

red (0.63-0.69)

NIR.(76-0.89)

Pan

1

0.45-0.9

0.61

EROS 1

Dec. 5, 2000

Pan

1

0.5-0.9

1.8

12.5

1-4 days

EO 1

Nov. 21, 2000

ALI

Multi

9

0.433-0.453

0.45-0.515

0.525-0.605

0.63-0.69

0.775-0.805

0.845-0.89

1.2-1.3

1.55-1.75

2.08-2.35

30

37

16 days

Pan

1

0.48-0.69

10

Hyperion

Hyper

220

0.4 to 2.5 (10nm sampling interval)

100 km

Satellite Name

Launch

Sensors

Types

No. of Bands

Spectral Range (microns)

(km)

Revisit Time

LAC

Hyper

256

0.9-1.6 (2-6nm sampling interval)

250

185 km

ASTER

Multi

3

VNIR - stereo (0.5-0.9)

15

6

SWIR (1.6-2.5)

30

60

16 days

5

TIR (8-12)

90

CERES

Multi

3

SWIR, TIR, Total

20 km

Terra

Dec. 18, 1999

MISR

Multi

4

250-275

360

(EOS AM-1)

MODIS

Multi

2

250

5

0.4-14.4

500

2330

29

1000

MOPITT

Multi

3

2.3 (CH4)

2.4 (CO)

22 km

640

4.7 (CO)

WPI

Multi

2

0.66 (green)

260

890

5 days

0.83 (NIR)

CBERS

October 14,

CCD (stereo)

Multi

5

0.51-0.73 (pan)

1999

0.45-0.52 (blue)

0.52-0.59 (green)

20

113

26 days

0.63-0.69 (red)

0.7-0.89 (NIR)

contd..

Satellite Name

Launch

Sensors

Types

No. of Bands

Spectral Range (microns)

(km)

Revisit Time

IR-MSS

Multi

4

0.5-1.1 (pan) 1.55-1.75 (IR) 2.08-2.35 (IR) 10.4-12.5 (TIR)

80 160

120

KITSAT-3

May 26, 1999

CCD

Multi

3

red, green, NIR

15

Pan

1

15

NOAA-K

May - 1998

AVHRR

Multi

5

1100

0.402-0.422

1130

2,800

1 day

0.433-0.453

0.48-0.5

OrbView-2

August, 1997

SeaWiFS

Multi

8

0.50-0.52

0.545-0.565

0.66-0.68

0.745-0.785

0.845-0.885

RADARSAT

November, 1995

SAR

(HH polarization)

8-120

24 days

ERS-2

1995

AMI

Radar

1

5.3 GHz(C-band)

26

99

35 days

ATSR

Multi

4

1000

05 CO

contd..

Satellite Name

Launch

Sensors

Types

No. of Bands

Spectral Range (microns)

(km)

Revisit Time

NOAA-14

1994

AVHRR

Multi

5

1100

RESURS-

1994

MSU-SK

Multi

4

0.5-0.6 (green)

170

600

21 days

01-3

0.6-0.7 (red)

0.7-0.8 (NIR)

0.8-1.1 (NIR)

1

10.4-12.6 (Thermal IR)

600

JERS-1

February, 1992

SAR

Radar

1

1275 MHz (L-band, HH polarization)

18

75

44 days

OPS

Multi

3

Visible NIR

18x24

75

4

SWIR

ERS-1

1991

AMI

(W polarization)

26

35 days

ATSR

Multi

4

1000

NOAA-12

1991

AVHRR

Multi

5

1100

CONCLUSIONS

Since the launch of first earth resource satellite in 1972, various satellite platforms with a variety of remote sensing sensors have been launched to study the earth, the ocean, the atmosphere and the environment. These earth resources satellites data are very useful for mapping and monitoring natural resources and environment at various levels, such as global, regional, local and micro level.

REFERENCES

Campbell, J.B. 1996. Introduction to Remote Sensing. Taylor & Francis, London.

Curran, P.J. 1985. Principles of Remote Sensing. Longman Group Limited, London.

Elachi C. 1987. Introduction to the Physics and Techniques of Remote Sensing. Wiley Series in Remote Sensing, New York.

http://www.ccrs.nrcan.gc.ca/ccrs/learn/tutorials/fundam/chapter1/chapter1_2.

http://www.ersc.edu/resources/EOSC.html

Joseph, G. 1996. Imaging Sensors for Remote Sensing. Remote Sensing Reviews, 13: 257342.

Lillesand, T.M. and Kiefer, R. 1993. Remote Sensing and Image Interpretation, Third Edition. John Villey, New York.

www.planetary.brown.edu/arc/sensor.html

www.spaceimage.com

www.eospso.gfc.nasa.gov

www.landsat.org

www.spotimage.fr/home

www.space.gc.ca

www.esa.int/export/esasa/ESADTOMBAMC_earth_O.html

0 0

Post a comment