Transcript Document
Active Microwave Satellites Dr. M. M. Yagoub E-mail: [email protected] E-mail: [email protected] URL : http://www.angelfire.com/mo/yagoub Over View • • • • • • • • • • • • 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 • • • • 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 • • • • • • • • • 22 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 – – – – – - ~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 • • • • – - 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