1. AE Review
Orbital Mechanics

2. Orbits are described by a set of parameters called….
orbital elements or Keplerian elements

3. The Keplerian element set consists of 6 parameters (plus a time stamp)
The Keplerian element set consists of 6 parameters (plus a time stamp). Name them.
Two of these describe the size and shape of an orbit:
Eccentricity (e)
Semi-major axis (a)
Three of these describe the orientation of the orbit in space:
Inclination (i)
Right ascension of the ascending node (W)
Argument of perigee (w)
One of these describes the location of the satellite within the orbit:
True anomaly (u)

4. An orbit with an inclination of 0 degrees is called an
equatorial orbit
polar orbit

5. An orbit with an inclination of 90 degrees is called a
equatorial orbit
polar orbit

6. A satellite in an equatorial orbit will pass
directly over the equator
over the entire Earth.

7. A satellite in polar orbit will pass
directly over the equator
over the entire Earth

8. Which two parameters can you determine from a ground trace?
Eccentricity (e)
Semi-major axis (a)
Inclination (i)
Right ascension of the ascending node (W)
Argument of perigee (w)
True anomaly (u)
Orbital Period
Inclination (i) and Orbital Period

9. Eccentricity of what value means the orbit is circular?
0 (zero)

10. What defines the point in an orbit that is farthest from Earth
Apogee

11. What describes the point in an orbit that is closest to Earth?
Perigee

12. When does Apogee Altitude = Perigee Altitude?
For a perfectly circular orbit

13. What parameter does this graphic describe?
Inclination

14. Determining a Satellite’s Orbital Period from its Ground Trace
Practice this.
Orbital Mechanics Modeling Slide 25

15. Right Ascension of the Ascending Node (RAAN, W )
Satellites may have identical eccentricities, semi- major axes, and inclinations (e, a, and i) yet may still be oriented differently in space – they can be “rotated” or “twisted” about the Earth in various ways

16. Argument of Perigee (w)
Argument of perigee describes the orientation of the orbit within the orbital plane

17. True Anomaly (u)
True anomaly is 0 degrees at perigee, 180 degrees at apogee

18. Kepler’s Laws
Know them
Orbital Mechanics Modeling Slide 31

19. LEO (Low Earth Orbit) Many Earth-observing satellites
Weather and imagery
Why is this?

20. GEO (Geostationary)
Achieved by placing the satellite in a special orbit where period exactly equals one day
Altitude: roughly 36,000 km (22,200 miles)
Inclination is exactly zero degrees
This is NOT close enough to get good images
Geostationary satellites mainly used for communications or “permanent relay station” in space

21. Molniya (Moly)
allows for long-term communications over their northern land mass.

22. Other things to review
A Problems