Lecture 2, Space Segment

Presentation / Lecture 2, Space Segment

Date Submitted: 06 June 2001

Written by RPC Telecommunications Ltd.. Website: http://www.rpctelecom.com

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This is the second in the series of general satcom tutorial lectures submitted by RPC Telecommunications.

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-Section 1
Orbit Theory: Kepler's Laws.
-Section 2
Orbit Theory: Formulae.
-Section 3
The Real World.
-Section 4
Types & Implications of Orbit.
-Section 5
Satellite Hardware.
-Section 6
Launch Vehicles.
-Section 7
Flight Plan & Maintaining Satellite In Orbit.
-Section 8
Stationkeeping & Stabilisation.

Types of Satellite Orbit

Geostationary Orbit
  • 24 hour period
  • 36,000 km altitude
  • circular orbit
  • always visible to an Earth station in the coverage area
  • zero (or very small) inclination for true geostationary case
  • still the most important orbit for telecommunications but overcrowding is a growing problem

Low Earth Orbit

  • short orbital period (few hours)
  • typically 100 - 600 km altitude
  • usually circular orbit
  • each satellite is only visible to an Earth station for typically less than one hour
  • often used in multi-satellite constellations
  • of growing interest at the present

Highly Elliptical Orbit

  • usually refers to special cases such as "Molniya" or "Tundra"
  • make use of special case solution to give zero precession of arguement of perigee (63.4 inclination)
  • Molniya has 24 hour period, perigee of 24,470 km and apogee of 47,100 km
  • very useful because when used in constellations they provide "quasi-stationary" coverage to higher latitudes which cannot be served by geostationary satellites

Intermediate Orbits

  • orbital periods typically several hours
  • typically 10,000 - 20,000 km altitude
  • Earth station visibility typically several hours
Satellite Orbit Implications On Design
  • What is the visible area of the Earth from each satellite?
  • Is satellite interlinking required?

Period & Visibility

  • How long can one Earth station see a satellite?
  • What arrangements are required to handover between satellites?

Environment & Power

  • Does the satellite need special arrangements to protect from radiation or to provide power capacity to deal with eclipse periods?

Number of satellites required?

Number of Earth stations required?

Next: Section 5 - Satellite Hardware.


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