Satellite Climatology - Orbits

Geostationary orbitsSun synchroneous orbitsPrecessing orbitDiscussion

Inclination

inclination

satellite orbit

perigee

plane of satellite orbit

equatorial plane

BasicsSatellites in circular orbitsattractive force Fg = m g (R/r)²centrifugal force Fc = m r ²m: mass of the satelliteR: radius of the earth (R = 6370 km)r: distance to the center of the earthg: acceleration of gravity (g = 9.81 m/s²): angular velocity ( = 2 f, f: rotation frequency)Stable orbitFg = Fc r=3 gR2

2πf 2

Satellite period and orbits

10 20 30 40 x106 m

24

20

16

12

8

4

radius

satellite period [h]velocity [ x1000 km/h]

synchronous distance35,786 km

Different Orbital Distances

1. geostationary orbit

Geostationary Geostationary OrbitOrbit

Geostationary Orbiting SatellitesGeostationary Orbiting Satellites

Satellite observes same area at all times. Satellite observes same area at all times. Continuous sampling.Continuous sampling.36000km from Earth’s surface!36000km from Earth’s surface!

2. Low sun synchroneous orbit

Polar Orbiting SatellitesPolar Orbiting Satellites

Satellite observes globe in “swaths”Satellite observes globe in “swaths”700-1700km from Earth’s surface700-1700km from Earth’s surface

Polar OrbitPolar Orbit

Polar Orbiting SatellitesPolar Orbiting Satellites

(Near) Polar Orbiting Satellites

Daily Coverage

3. Precessing orbit

Orbits shown in inertial space and size relative to Earth is correct

Other orbits

Discussion: what's the effect of orbit on:

Science:Viewing zenith angles?Revisit time?Diurnal cycle?Coverage?Tropics/polar regions?Sun glint?

Technical:Data transmission?Data reception?Solar panel?Instruments optics?Space weather?Debris?Orbital drift?

Worldwide Operational Weather Worldwide Operational Weather Satellite ObservingSatellite Observing

Polar RegionsThe satellite doesn't pass directly over the pole due to the slight inclination of the orbital plane. The transparent overlay identifies the 3000 km wide swath that is viewed by the AVHRR imaging instrument on the satellite. The yellow curves delineate the limits of the 60 degree viewing arcs from the six "standard" geostationary satellites included in these discussions.

Satellite Constellation

A group of electronic satellites working in concert is known as a satellite constellation. Such a constellation can be considered to be a number of satellites with coordinated ground coverage, operating together under shared control, synchronised so that they overlap well in coverage and complement rather than interfere with other satellites' coverage.

Satellite Formation