satellite orbits satellite meteorology/climatology professor menglin jin

Download Satellite Orbits Satellite Meteorology/Climatology Professor Menglin Jin

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  • Slide 1
  • Satellite Orbits Satellite Meteorology/Climatology Professor Menglin Jin
  • Slide 2
  • Satellite Orbits n At what location is the satellite looking? n When is the satellite looking at a given location? n How often is the satellite looking at a given location? n At what angle is the satellite viewing a given location?
  • Slide 3
  • Atmospheric Remote Sensing Sensors, Satellite Platforms, and Orbits n Satellite orbits and platforms Low Earth orbitLow Earth orbit Sunsynchronous and repeat coverage Precessing Geosynchronous orbitGeosynchronous orbit n Sensor scanning modes Whiskbroom and pushbroom scannersWhiskbroom and pushbroom scanners Active and passive microwave radiometersActive and passive microwave radiometers
  • Slide 4
  • Types of orbits n Sunsynchronous orbits: An orbit in which the satellite passes every location at the same time each day Noon satellites: pass over near noon and midnightNoon satellites: pass over near noon and midnight Morning satellites: pass over near dawn and duskMorning satellites: pass over near dawn and dusk Often referred to as polar orbiters because of the high latitudes they crossOften referred to as polar orbiters because of the high latitudes they cross Usually orbit within several hundred to a few thousand km from EarthUsually orbit within several hundred to a few thousand km from Earth
  • Slide 5
  • Types of orbits n Geostationary (geosynchronous) orbits: An orbit which places the satellite above the same location at all times Must be orbiting approximately 36,000 km above the EarthMust be orbiting approximately 36,000 km above the Earth Satellite can only see one hemisphereSatellite can only see one hemisphere
  • Slide 6
  • Geosynchronous Meteorological Satellites WMO Member States
  • Slide 7
  • Low Earth Orbit Concepts Equator South Pole Ground track Ascending node Inclination angle Descending node Orbit Perigee Apogee Orbit
  • Slide 8
  • Sun-Synchronous Polar Orbit Satellit e Orbit Earth Revolution Satellite orbit precesses (retrograde) 360 in one year Maintains equatorial illumination angle constant throughout the year ~10:30 AM in this example Equatorial illumination angle
  • Slide 9
  • Sun-Synchronous Orbit of Terra
  • Slide 10
  • Spacing Between Adjacent Landsat 5 or 7 Orbit Tracks at the Equator
  • Slide 11
  • Timing of Adjacent Landsat 5 or 7 Coverage Tracks Adjacent swaths are imaged 7 days apart
  • Slide 12
  • Polar-Orbiting Satellite in Low Earth Orbit (LEO) Example from Aqua
  • Slide 13
  • q A precessing low- inclination (35 ), low-altitude (350 km) orbit to achieve high spatial resolution and capture the diurnal variation of tropical rainfall Raised to 402 km in August 2001 Tropical Rainfall Measuring Mission Orbit (Precessing)
  • Slide 14
  • TRMM Coverage 1 day coverage2 day coverage
  • Slide 15
  • The orbital period of a satellite around a planet is given by where 0 = orbital period (sec) R p =planet radius (6380 km for Earth) H=orbit altitude above planets surface (km) g s =acceleration due to gravity (0.00981 km s -2 for Earth) Definition of Orbital Period of a Satellite
  • Slide 16
  • Orbital Characteristics of Selected Missions Low Earth Orbit & Precessing Missions
  • Slide 17
  • Ellipse n An ellipse is defined as follows: For two given points, the foci, an ellipse is the locus of points such that the sum of the distance to each focus is constant. focilocussumconstantfocilocussumconstant n BTW, Locus-A word for a set of points that forms a geometric figure or graph setpointsgeometric figuregraphsetpointsgeometric figuregraph
  • Slide 18
  • Keplers laws 1. Satellites follow an elliptical orbit with the Earth as one focus Perigee Apogee Foci
  • Slide 19
  • Period of orbit n Valid only for circular orbits (but a good approximation for most satellites) n Radius is measured from the center of the Earth (satellite altitude+Earths radius) n Accurate periods of elliptical orbits can be determined with Keplers Equation T 2 = r 3 4242 Gm e Period of orbit Gravitational constantMass of the Earth Radius of the orbit
  • Slide 20
  • Sunsynchronous image (SMMR)
  • Slide 21
  • Geostationary Image (GOES-8)
  • Slide 22
  • Space-time sampling n Geostationary Fixed (relatively) field of viewFixed (relatively) field of view View area of about 42% of Earths surfaceView area of about 42% of Earths surface n Sunsynchronous Overlapping viewsOverlapping views See each point at several viewing anglesSee each point at several viewing angles n Other orbits (walking orbits) Passes each location at a different time of dayPasses each location at a different time of day Earth Radiation Budget SatelliteEarth Radiation Budget Satellite Useful when dirunal information is neededUseful when dirunal information is needed
  • Slide 23
  • Scanning techniques n Vidicom Like television camera; sees everything at onceLike television camera; sees everything at once n Swinging Results in a zig-zag pattern of scanningResults in a zig-zag pattern of scanning n Spinning Satellite spins in order to create imageSatellite spins in order to create image n Pushbroom Multiple scanning elements, relies on forward motion of satelliteMultiple scanning elements, relies on forward motion of satellite

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