1. Sun – Earth System Understanding Orbits Earth’s rotation axis Equator
Sun’s rays
Orbiting Spacecraft
Eclipse
Equator
Spacecraft orbit
SSE-120

2. Earth System Understanding Orbits q r h Orbit plane Orbit inclination
Earth radius h
Orbit altitude
SSE-120

3. Earth’s rotation around the sun
Understanding Orbits
Earth’s rotation around the sun
Equinox
Winter
Summer
Equinox
SSE-120

4. Launching a spacecraft
Understanding Orbits
Launching a spacecraft
SSE-120

5. All orbits go thru the center of the earth
Understanding Orbits
All orbits go thru the center of the earth
SSE-120

6. Launching a spacecraft into a terminator orbit
Understanding Orbits
Launching a spacecraft into a terminator orbit
SSE-120

7. Launching a spacecraft into a terminator orbit
Understanding Orbits
Launching a spacecraft into a terminator orbit
SSE-120

8. Launching a spacecraft into a terminator orbit
Understanding Orbits
Launching a spacecraft into a terminator orbit
SSE-120

9. Spacecraft enters eclipse
Understanding Orbits
Spacecraft enters eclipse
Launching at noon or midnight
Spacecraft leaves eclipse
SSE-120

10. f = Q - 180 Understanding Orbits
Calculating eclipse time for a noon-midnight orbit d h r
r + h q f q
Solution
d = [(r + h)2 – r2]1/2
Q = cos-1 [r/(r+h)]
f = Q - 180
Eclipse time = [(2* f)/360] * orbit time
SSE-120