Celebrating 25 Years of Achievement 17 August 2000 Dr. Charles Randell P.Eng TransCanada...
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Transcript of 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
Celebrating 25 Years of Achievement
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
Celebrating 25 Years of Achievement
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
Celebrating 25 Years of Achievement
Celebrating 25 Years of Achievement
Spacecraft parameter:orbit periodserviceable life
Sensor parameterstype of sensortemporal resolution (tied
to orbit)spatial resolutionradiometric resolutionspectral resolution
Satellite Specifications
Celebrating 25 Years of Achievement
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
Celebrating 25 Years of Achievement
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
Celebrating 25 Years of Achievement
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
Celebrating 25 Years of Achievement
Image with 25 m resolution
Spatial resolution:
Celebrating 25 Years of Achievement
Image with 5 m resolution
Spatial resolution:
Celebrating 25 Years of Achievement
Image with 1 m resolution
Celebrating 25 Years of Achievement
8 bit multispectral image
green +
red +
blue =
Spectral resolution
Celebrating 25 Years of Achievement
Reduced radiometric resolution - 3 bit image
Celebrating 25 Years of Achievement
Panchromatic (grayscale) image
Celebrating 25 Years of Achievement
Currently 2 Types of Imaging Sensors on Satellites
1. Synthetic Aperture Radar (SAR)
2. Optical- panchromatic- multispectral
Celebrating 25 Years of Achievement
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)
Celebrating 25 Years of Achievement
• Radar not optical image
• prone to noise
• interpretation not “intuitive”
• “complex” data permits very power techniques for information extraction
SAR Satellites
Celebrating 25 Years of Achievement
Oil slick in falsecolored SAR Image
Celebrating 25 Years of Achievement
RADARSAT Receiving Stations
Celebrating 25 Years of Achievement
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
Celebrating 25 Years of Achievement
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
Celebrating 25 Years of Achievement
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
Celebrating 25 Years of Achievement
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
Celebrating 25 Years of Achievement
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)
Celebrating 25 Years of Achievement
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