Presentation on theme: "Remote Sensing & Geodesy. What is remote sensing? History of satellite remote sensing Satellite orbits Geophysical Examples: Multispectral, GPS, Radar/INSAR,"— Presentation transcript:
What is remote sensing? History of satellite remote sensing Satellite orbits Geophysical Examples: Multispectral, GPS, Radar/INSAR, Satellite Gravity Geodesy
What is Remote Sensing? … the science of deriving information about Earth's land and water areas from images acquired at a distance
Starting in 1946, captured V-2 rockets were launched to > 100 km by the U.S. Army Launch 13 in the V-2 series contained a motion picture camera in its nose cone, which acquired a series of views of the Earth's surface as it proceeded to a 134 km altitude. http://rst.gsfc.nasa.gov/
The Soviet Union surprised the world when it launched Sputnik, the world's first satellite, on October 4, 1957. The U.S. quickly followed suit: Explorer I, was launched into Earth orbit on Jan. 31, 1958 and discovered the Van Allen radiation belts (above, right). In the 1960’s spy planes and satellites were common (e.g., right: Cuban missile crisis).
http://geo.arc.nasa.gov/sge/landsat/ The first Landsat satellite was launched in 1972; the most recent, Landsat 7, was launched on April 15, 1999. Images are archived at Landsat receiving stations and used for global change research and applications in agriculture, geology, forestry, regional planning, education and national security. Landsat S.F. Bay Area
Communications satellites use a geostationary orbit, in which the satellite is always in the same position (above the equator) with respect to the rotating Earth. Geostationary orbits are high altitude (35700 km) Geostationary T 2 = A r 3 M A = 5.92x10 11 s 2 kg/m 3 Kepler’s 3 rd Law Satellite Orbits
Many remote-sensing satellites use a polar orbit to provide a more global view of Earth These satellites operate in a sun- synchronous orbit at an altitude of 700 to 800 km. Polar T 2 = A r 3 M A = 5.92x10 11 s 2 kg/m 3 Kepler’s 3 rd Law Satellite Orbits
MSI systems are passive devices that measure electromagnetic waves (e.g. light, infrared) at different wavelengths, then combine the results Example: Landsat Thematic Mapper (TM) images are produced using 7 different spectral bands http://www.classzone.com/books/earth_science/terc/content/investigations/esu101/esu101page07.cfm Multispectral Imaging Systems
http://www.classzone.com/books/earth_science/terc/content/investigations/esu101/esu101page07.cfm Multispectral Imaging Systems
Global Positioning System The Global Positioning System is a network of 24 satellites placed into orbit by the U.S. Department of Defense. The satellites circle the earth twice a day in a very precise orbit and transmit information to earth.
Global Positioning System A GPS location is pinpointed using triangulation from 3 or more satellites. Today, GPS is used extensively for navigation and geodetic studies. http://pasadena.wr.usgs.gov/office/hudnut/scec/97 _SCEC_E_summary.html
Satellite Radar Systems Radar satellites (e.g., ERS2, Radarsat) are active systems that reflect radar beams from Earth’s surface. Radar waves can pass through clouds and so provide more continuous coverage of the surface
Satellite Radar Systems Since the satellite orbits approximately repeat, radar images of the same region can be compared (radar interferometry) Interferometric synthetic aperture radar (InSAR) techniques are used to study dynamic systems (e.g., Indian earthquake on right) http://www.gfz-potsdam.de/ http://www.gfz-potsdam.de/ pb1/pg5/research/methods/insar/insar_uk.html
Satellite Gravity Systems CHAMP (CHAllenging Minisatellite Payload), launched July 15, 2000, is a German small satellite mission that measures Earth’s gravity using precise GPS orbital data
Satellite Gravity Systems The Gravity Recovery and Climate Experiment (GRACE) March 2002 mission detects changes in Earth’s gravity field by monitoring the distance between the two satellites The trailing spacecraft is actually about 220 kilometers behind the lead spacecraft.
Satellite Gravity Data http://www.csr.utexas.edu/grace/gravity/solid_earth.html New data from satellite gravity missions is being used for plate tectonic research Note improvement in the resolution of gravity anomalies in Tonga trench region
Geodesy: Study of Earth’s shape The Earth is not quite a perfect sphere This shape is called the reference ellipsoid (RE) RE has the shape of a drop of ideal fluid rotating at same velocity as Earth! http://earth.leeds.ac.uk/dynamicearth/internal/shape.htm
Geodesy: Study of Earth’s shape Geoid: The hypothetical Earth surface that coincides with sea level everywhere. Usually, the Reference Ellipsoid is used for a datum. Large-scale Geoid anomalies reflect the mass distribution in Earth’s mantle.
Geoid 100m Geoid low in the Indian ocean 70m Geoid high in the SW Pacific