celebrating 25 years of achievement 17 august 2000 dr. charles randell p.eng transcanada...

Celebrating 25 Years of Achievement

17 August 2000

Dr. Charles Randell P.Eng

TransCanada Transmission &

Colonial Pipeline Company

EO Satellite Primer


2 Main Categories of Satellites

Geostationary satellites:

- stationary above a fixed point on the equator

- “footprint” does not change

- orbits very high (1000s of km) above earth

- typically communications and weather satellites

GOES Image36000 km orbit1 - 4 km resolution


Polar (near polar) orbiting satellites:

- lower orbits (100s of km)

- orbit follows a pattern that takes it near the poles

- “footprint” moving continuously in periodic pattern. Repeats every 25-35 days.

- “earth observation” (EO) satellites

2 Main Categories of Satellites



Spacecraft parameter:orbit periodserviceable life

Sensor parameterstype of sensortemporal resolution (tied

to orbit)spatial resolutionradiometric resolutionspectral resolution

Satellite Specifications


Temporal resolution:

Revisit time, or how often you can “see” the same area on earth

Many sensor have overlapping swaths so it is possible to see the same spot on earth every 1 - 5 days.

Seeing the same spot from the same perspective, or point in space depends on repeat period of the spacecraft. This is important for certain subtle change analyses.

Use more than onesatellite to increase revisit frequency


Spatial resolution:

Minimum spacing between two points for which they can be individually distinguished.

Generally accepted “working definition”:

area on the ground covered by each pixel


Satellite imagery is digital:

Numerically it is a matrix where eachmatrix element contains a number corresponding to the image picture element - pixel

The number may be real or complex

For optical images, the number represents intensity of the pixel

For radar images, the number represents a magnitude and phase30 28 27 28 36 40 42

31 28 27 40 36

44 42 31 40 38 17 10 1


Image with 25 m resolution

Spatial resolution:



Spatial resolution:


8 bit multispectral image

green +

red +

blue =

Spectral resolution


Reduced radiometric resolution - 3 bit image


Panchromatic (grayscale) image


Currently 2 Types of Imaging Sensors on Satellites

1. Synthetic Aperture Radar (SAR)

2. Optical- panchromatic- multispectral


SAR Satellites

SAR is an active radar

• Penetrates cloud & fog

• penetrates darkness

• very reliable coverage

RADARSAT Fine Beam Image (this clip 9 km × 11 km)


• Radar not optical image

• prone to noise

• interpretation not “intuitive”

• “complex” data permits very power techniques for information extraction

SAR Satellites


Oil slick in falsecolored SAR Image


RADARSAT Receiving Stations


SAR SatellitesSAR Satellite Mission Date Frequency

(GHz)Resolution

(m)

Seasat 1978 June – October 1.3 L-band 25SIR-A 1981 November 1.3 L-band 40SIR-B 1984 October 1.3 L-band 17–58Almaz-1 1991 March – 1993 3.0 S-band 15–30JERS-1 1992 February – 1998 1.3 L-band 18ERS-1 1991 July – 1996 (1999) 5.3 C-band 20–30SIR-C/X-SAR 1994 April 1.3 L-band

5.3 C-band9.6 X-band

25–200

SRTM 2000 February 5.3 C-band9.6 X-band

30

ERS-2 1995 April – 5.3 C-band 20–30RADARSAT-1 1995 November – 5.3 C-band 8–100

ENVISAT 2001 June 5.3 C-band 30–150

RADARSAT-2 2002 5.3 C-band 3–100PALSAR

TerraSAR

2001 Q1 J-band 10–100

2004 L/X-band 1


Optical Satellites

Optical equipped satellitesare passive imaging systems.Effectively cameras in space.

• Interpretation more intuitive

• Subject to usual visibility limitations

• Multiple spectral bands permit detection/classification of numerous phenomena

• Subject to “usual” visibility limitations

• Interpretation more intuitve

• Multiple bands permit reliable detection of numerous phenomena

IKONOS 4m multispectral image


Multispectral and hyperspectral imagery good for detecting color and anomalous regions such as stressed vegetation, moisture changes, temperature change, and local atmospheric anomolies

Hyperspectral image of oil from underground pipeline serving Chaulk Point Generating Station, MD. Ruptured April 7, 2000


Optical Satellites

Optical satellites have recently passed a milestone in commercialcapability

“Taskable” satellites with 1 meter resolution• Multiple bands permit reliable detection of

numerous phenomena

IKONOS 1m panchromatic imageSawmill & lumber yard


Satellite Revisit Data Launch Time Delivery Date

IKONOS-2 2 days 1+ days operational

EROS-A1 2-3 days - Q4 ‘00(1st of 8)

Orbview-3 < 3 days - Jan '01

Quickbird 1-5 days - 2001

Encroachment and Gas DetectionOptical Satellites (1m / 4m resolution)


Summary:

•Two types of EO satellites: SAR & optical

•Highest resolutions range from 1 m to 30 m

•Data can be available within hours

•EO satellites where traditionally for scientific and government use

•Current and future satellite missions designed with commercial/industrial applications in mind

celebrating 25 years of achievement 17 august 2000 dr. charles randell p.eng transcanada...

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