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Satellite Orbits. Satellite Meteorology/Climatology Professor Menglin Jin. Satellite Orbits. At what location is the satellite looking? When is the satellite looking at a given location? How often is the satellite looking at a given location?

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satellite orbits

Satellite Orbits

Satellite Meteorology/Climatology

Professor Menglin Jin

satellite orbits1
Satellite Orbits
  • At what location is the satellite looking?
  • When is the satellite looking at a given location?
  • How often is the satellite looking at a given location?
  • At what angle is the satellite viewing a given location?
atmospheric remote sensing sensors satellite platforms and orbits
Atmospheric Remote Sensing Sensors, Satellite Platforms, and Orbits
  • Satellite orbits and platforms
    • Low Earth orbit
      • Sunsynchronous and repeat coverage
      • Precessing
    • Geosynchronous orbit
  • Sensor scanning modes
    • Whiskbroom and pushbroom scanners
    • Active and passive microwave radiometers
types of orbits
Types of orbits
  • Sunsynchronous orbits: An orbit in which the satellite passes every location at the same time each day
    • Noon satellites: pass over near noon and midnight
    • Morning satellites: pass over near dawn and dusk
    • Often referred to as “polar orbiters” because of the high latitudes they cross
    • Usually orbit within several hundred to a few thousand km from Earth
types of orbits1
Types of orbits
  • 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 Earth
    • Satellite can only “see” one hemisphere
low earth orbit concepts
Low Earth Orbit Concepts

Descending node

Ascending node


Ground track


Inclination angle



South Pole


sun synchronous polar orbit
Sun-Synchronous Polar Orbit

Earth Revolution

Equatorial illumination angle

Satellite Orbit

  • Satellite orbit precesses (retrograde)
    • 360° in one year
  • Maintains equatorial illumination angle constant throughout the year
    • ~10:30 AM in this example
timing of adjacent landsat 5 or 7 coverage tracks
Timing of Adjacent Landsat 5 or 7 Coverage Tracks

Adjacent swaths are imaged 7 days apart

tropical rainfall measuring mission orbit precessing
Tropical Rainfall Measuring Mission Orbit (Precessing)
  • 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
trmm coverage
TRMM Coverage

1 day coverage

2 day coverage

definition of orbital period of a satellite
Definition of Orbital Period of a Satellite

The orbital period of a satellite around a planet is given by


T0 = orbital period (sec)

Rp = planet radius (6380 km for Earth)

H¢ = orbit altitude above planet’s surface (km)

gs = acceleration due to gravity (0.00981 km s-2 for Earth)

  • 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.
  • BTW, Locus-A word for a set of points that forms a geometric figure or graph
kepler s laws
Kepler’s laws

1. Satellites follow an elliptical orbit with the Earth as one focus




period of orbit
Period of orbit

Period of orbit


T2= r3

  • Valid only for circular orbits (but a good approximation for most satellites)
  • Radius is measured from the center of the Earth (satellite altitude+Earth’s radius)
  • Accurate periods of elliptical orbits can be determined with Kepler’s Equation


Radius of the orbit

Gravitational constant

Mass of the Earth

space time sampling
Space-time sampling
  • Geostationary
    • Fixed (relatively) field of view
    • View area of about 42% of Earth’s surface
  • Sunsynchronous
    • Overlapping views
    • See each point at several viewing angles
  • Other orbits (“walking orbits”)
    • Passes each location at a different time of day
    • Earth Radiation Budget Satellite
    • Useful when dirunal information is needed
scanning techniques
Scanning techniques
  • Vidicom
    • Like television camera; “sees” everything at once
  • Swinging
    • Results in a zig-zag pattern of scanning
  • Spinning
    • Satellite spins in order to create image
  • Pushbroom
    • Multiple scanning elements, relies on forward motion of satellite