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Satellite fundamentals
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Some Satellite Basics
Low Earth Orbit (LEO):Orbiting at an altitude of
600-1,000 km.
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Path of Satellite
NASA Earth-Observing Satellites
Ascending Orbit:The satellite is moving South to North when that portion of the orbit track crosses the equator.
Low Earth Orbit:Orbiting at an
altitude of 600-1,000 km.
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Path of Satellite
Ascending Orbit:The satellite is moving South to North when that portion of the orbit track crosses the equator.
NASA Earth-Observing Satellites
Ascending Orbit:The satellite is moving South to North when that portion of the orbit track crosses the equator.
Descending Orbit:The satellite is
moving North to South when that
portion of the orbit track crosses the
equator.
Low Earth Orbit:Orbiting at an
altitude of 600-1,000 km.
33
Descending Orbit:The satellite is
moving North to South when that
portion of the orbit track crosses the
equator.
NASA Earth-Observing Satellites
Ascending Orbit:The satellite is moving South to North when that portion of the orbit track crosses the equator.
Descending Orbit:The satellite is moving
North to South when that portion of the orbit track
crosses the equator.
Low Earth Orbit:Orbiting at an
altitude of 600-1,000 km.
44
Ascending vs. descending
orbits are like night and day!
NASA Earth-Observing Satellites
Sun-Synchronous:The satellite is always in the same relative position between the Earth and Sun.
Ascending Orbit:The satellite is moving South to North when that portion of the orbit track crosses the equator.
Descending Orbit:The satellite is moving
North to South when that portion of the orbit track
crosses the equator.
Low Earth Orbit:Orbiting at an
altitude of 600-1,000 km.
55
NASA Earth-Observing Satellites
Sun-Synchronous:The satellite is always in the same relative position between the Earth and Sun.
Ascending Orbit:The satellite is moving South to North when that portion of the orbit track crosses the equator.
Descending Orbit:The satellite is moving
North to South when that portion of the orbit track
crosses the equator.
Period:A typical polar, Sun-
synchronous LEO satellite takes about
90 minutes to completely circle the
Earth. This gives it about 16 orbits per
day.
Low Earth Orbit:Orbiting at an
altitude of 600-1,000 km.
66
Period:A typical polar, Sun-synchronous LEO satellite takes about 90 minutes to completely circle the Earth. This gives it about 16 orbits per day.
NASA Earth-Observing Satellites
Sun-Synchronous:The satellite is always in the same relative position between the Earth and Sun.
Equatorial-Crossing Time:The local apparent solar time when the satellite crosses the equator.
Example: Terra has an equatorial crossing time of 10:30 am, and is called an “AM” or morning satellite.
Ascending Orbit:The satellite is moving South to North when that portion of the orbit track crosses the equator.
Descending Orbit:The satellite is moving
North to South when that portion of the orbit track
crosses the equator.
Period:A typical polar, Sun-
synchronous LEO satellite takes about 90 minutes to completely
circle the Earth. This gives it about 16
orbits per day.
Low Earth Orbit:Orbiting at an
altitude of 600-1,000 km.
77
Satellite InclinationHigh Inclination or Polar Orbit
(near 90º)
virtually complete global
coverage
88
Low Inclination Orbit (often near 57º--
Space Shuttle)
no polar coverage
Equator
Inclination: The position of the orbital plane relative to the equator. For near-polar orbits, typically about 97º.
Sun-Synchronous Orbit of TerraSun-Synchronous Orbit of Terra
• Near-polar, sun-synchronous, orbiting the Earth every 98.8 minutes, crossing the equator going north (daytime ascending) at 1:30 p.m. and going south at 1:30 a.m.
• The orbit track changes every day but will repeat on a 16 day cycle. This is true for both Aqua and Terra.
Aqua’s OrbitAqua’s Orbit
Polar-Orbiting Satellite in Low Earth Orbit (LEO)Polar-Orbiting Satellite in Low Earth Orbit (LEO)
Example from Aqua
Daytime Orbits
Terra - Descending Aqua - Ascending
When looking at an image of a piece of the orbit the two sensorswill have opposite ‘tilts’.
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