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Active Microwave Satellites
Dr. M. M. Yagoub
E-mail: [email protected]
E-mail: [email protected]
URL : http://www.angelfire.com/mo/yagoub
Over View
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Active Microwave sensors
Microwave Spectrum
Remote Sensing Principles
Passive and Microwave Concept
RADAR
Radar Geometry
Orbit Types
Side Looking Aperature Radar (SLAR)
Seasat
European Remote Sensing Satellite (ERS)
Japanes Remote Sensing Satellite (JERS)
Canadian SAR
Type of Remote Sensing
Sensor
Wavelength
Region
Visible Reflective infrared
Source
Sun
Object
Reflectance
Electromagneti
c
Spectrum
RADAR System
Optical Sensor System
Visible
0.4 mm
Microwave
Thermal infrared
Transmitted by
Object
Remote sensing
System
Thermal radiation
(temperature, emissivity)
Reflective infrared - Thermal infrared
0.7 mm
3.0 mm
10 mm
1 mm
Backscattering
coefficient
Microwave
Microwave portion is generally longer
wavelengths > 1mm to 1m range
Remote Sensing Principles
Orbit Types
Near Polar
Geo-stationary
Sun-synchronous
Geo-synchronous
Passive and Microwave Concept
Microwave devices may be active or passive
Passive
Passive Microwave
very low reflection
RADAR (Radio Detection And Ranging)
• -The concept of active microwave or RADAR is that an
energy pulse is sent out from an antenna and the return
signal (if any) is recorded. In essence this is similar to a
camera flash. In this respect reflectance (specular and
diffuse) become very important as to the di-electric
characteristics (ability to conduct / transmit) of the material.
• -Penetration (cloud, vegetation) is achieved when  >>
particle size / leaf area
• -Radar images usually contain considerable high frequency
noise (salt and pepper appearance) and are geometrically
distorted. In actual fact some features can appear vastly
different while different objects can appear the same due to
their surface nature
RADAR
• RADAR is very difficult to interpret and requires a
significant amount of post-processing before it can be
used with any level of confidence
• Microwaves will penetrate cloud, rain, smoke and smog
so images may be captured in any weather
• Images may be captured equally well in the night as
day
• Microwaves in longer wavelengths can penetrate
vegetation canopies, loose dry soil and similar
'interfering' surfaces.
• However, if radar is chosen as an imaging source one
must accept the poor geometric quality and unusual
object response
• SAR - Synthetic Aperture Radar (Vertical, need large
antenna)
• SLAR - Side-Looking Airborne Radar (the imagery
obtained occurs to the side of the aircraft)
SLAR Operation
• 1. Microwave energy transmitted in short pulses
(microsecond periods)
• 2. Pulse moves outward until it reaches an object
that reflects the pulse - either absorbs, specular,
diffuse or corner-cube / multi-path
• 3. Reflected energy pulse from the object reaches
the antenna with a signal magnitude (Magnitude
varies depending on objects reflectivity
characteristics and angular relationships)
• 4. Return signal (amplitude / time signal) strength is
recorded and distance to each object (slant range) is
determined (ie. response and slant distance measured
and recorded)
Radar Geometry
Look Direction
Range
Slant distance
Radar Geometry
SPATIAL RESOLUTION Of RADAR
• The spatial resolution of RADAR is controlled by pulse
length and beam width.
• Pulse Length is the duration the signal is transmitted.
This determines the across track (Y) spatial resolution.
This is called the range resolution and is in the
direction of energy propagation (range direction).
• Beam width is the width of the antenna. This
determines the spatial resolution in the azimuth (X)
direction.
• Response for a feature is determined by: Geometric
characteristics - orientation, roughness, slope and
Dielectric characteristics - determines reflective and
conductive interaction
Radar Geometry
Shadow
Satellites based on Microwave
- US SEASAT
- European Remote Sensing Satellites (ERS)
- Japanese Earth Resource Satellite (JESRS)
- Canadian RADARSAT
Sea Sat
SEASAT and SIR
• SEASAT
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was launched on June 1978 carrying
onboard SAR ( = 23cm) for oceanographic
studies. The system failed on October 1978
Shuttle Imaging Radar (SIR) using space shuttle
SIR-A: 1981 at an altitude of 260 kilometres
above the earth (flight SIR-A- 54 Hours mission,
 = 23.5cm)
SIR-B: Same characteristics as above
SIR-C/X-SAR System: Launched in 1994 with
frequencies of x-band (3cm), C-band(6 cm) and Lband (23 cm) with swath width of 15 to 90 Km
and 10 to 20 m resolution
European Remote Sensing Satellites (ERS)
• The European Space Agency (ESA) launched a series of
active remote sensing satellites such as ERS-1, 2, and
ENVISAT.
• ERS-1 was Launched in 1991 at an altitude of 782-785
km, an inclination of 98.5 deg, Near-circular, polar, Sunsynchronous and ground swath width 80 Km
• Onboard sensors: Synthetic Aperture Radar (SAR),
Scatterometer (Wind), Radar altimeter (sea depth), ATSR
• Temporal resolution (Repeat cycle: 3-day, 35-day and 176day)
• ERS-2: Launched in 1995, Largely identical to ERS-1
• Onboard sensors are (SAR) with resolution 20-30m,
Scattero-meter, ATSR, and Global Ozone Monitoring
Experiment (GOME)
ERS Sensors
Environmental Satellite (ENVISAT)
• Owner: ESA (European Space Operation Center-ESOC- in
Darmstad, Germany)
• Date of launch: 1 March 2002
• Altitude: 800 km
• Orbit: Sun-synchronous
• Instruments: 10, covering wide spectrum of phenomena
(atmosphere, Oceans, vegetation, human activity, polar
ice)
• Solar array: 65 square meters
• The satellite provides a major tool for environmental
monitoring worldwide and within Europe (European
Global Monitoring for Environment and Security –GMES)
Japanese Earth Resource Satellite JERS-1
(NASDA and MITI)
• Launched in 1992 in a sun synchronous orbit
at an altitude of approximately 570km and
inclination of approximately 98 deg
• Period : Approx. 96 min.
• Recurrent period : 44 days
• Onboard sensors are SAR (Synthetic Aperture
Radar), which is an active microwave sensor,
and OPS, an optical sensor that measures light
reflected from the earth's surface ranging
from visible light to short wave infrared light
Japan: NASDA -NAtional Space
Development Agency
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Advanced Land Observing Satellite [ALOS]
Tropical Rainfall Measuring Mission [TRMM]
Advanced Earth Observing Satellite II [ADEOS-II]
Advanced Earth Observing Satellite [ADEOS]
Japanese Earth Resource Satellite JERS-1
Marine Observation Satellites MOS-1/MOS-1b
Geostationary Meteorological Satellites- GMS1-5
Experimental Geodetic Satellite EGS
Ionosphere Sounding Satellites ISS-b
RadarSat
http://www.ccrs.nrcan.gc.ca/ccrs/tekr
d/radarsat/rsate.html
RADARSAT
• RADARSAT is Canada's first series of remote
sensing satellites, starting with RADARSAT-1
launched in 1995 and followed by RADARSAT-2,
planned for launch in 2002.
• These satellites focus on the use of radar sensors
in order to provide unique information about the
Earth's surface through most weather conditions
and even darkness
• Onboard sensor is SAR with frequency of
5.3GHz, range resolution 25 m and azimuth
resolution of 28 m, Swath Width of 100km
RADARSAT SAR Characteristics
• Frequency: 5.3 GHz
• Polarization: HH
• Aspect
– - Right-looking (North) SAR
– - Left-looking (Antarctica)
• SAR On-Time
– - 28 minutes/orbit
– - (12 Minutes for Antarctica)
RADARSAT SAR Characteristics
RADARSAT SAR operating modes
• Standard, Wide, and Fine Resolution Mode
• Standard Mode:
• 7 Beams, >10% overlap
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- ~250km nadir offset
- Swath Width: 100km
- Range Resolution(1): 25m
- Azimuth Resolution: 28m
- Looks(2): 4
– - Incidence Angle Range(3): 20-49°
RADARSAT Orbit Characteristics
• Geometry
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– - Circular, sun-synchronous (dawn-dusk)
– - Ascending Node: 18:00 +/- 15 local time
Altitude: 798 km
Inclination: 98.6°
Period: 100.7 Minutes
Repeat Cycle
– - 24 days (14 7/24 orbits per day)
– - 7 day & 3 days sub-cycles
• Coverage
– - Global: 4,5 days
– - North America: 3 days
RADARSAT Orbit Characteristics
SAR Contour
SAR shadow
DEM
Image Types
Real
Infrared:Red Vegetation
RADAR Web sites
• http://skuld.cage.curtin.edu.au/~farmerd
a/ARS98/
• http://southport.jpl.nasa.gov/desc/imagingra
darv3.html
• http://www.asf.alaska.edu/reference_docum
ents/sensor_references/sar_theory.html
• http://www.ccrs.nrcan.gc.ca/ccrs/tekrd/radar
sat/rsate.html
International Space Station (ISS)
• Partners: NASA, ESA, the Russian, Japanese, and Canadian Space
Agencies
• Permanent Crew capacity: Six/Seven
• Orbit: 90 minutes to circle the Earth
• Inclination: 51.6 degrees to the Equator
• Altitude: 400 km (average) above the Earth
• Dimensions: 108 m long x 80 m wide (size of a modern football
stadium)
• Mass weight: 455865 kg
• Living volume : 1200 m3
• Applications: Testing of human ability to live in space (medical,
psychological, physical), space tours, and monitoring of environment