OEM 101 Day 2 Classical Orbital Elements and Reference Frames
Which frame of reference is used to describe ground tracks?
ECEF
Semi-major axis is the _____ of your orbit.
Size
What is the symbol for the argument of perigee?
ω
What is the range for the semi-major axis?
0° < ∞
What is the range for inclination?
0° → 180°
What is the range for RAAN?
0° → 360°
What is the range for argument of perigee?
0° → 360°
What is the range for true anomaly?
0° → 360°
What is the range for eccentricity?
0° → ∞
What is a perifocal frame?
A frame of reference for an orbit.
Fill in what e's range is for the following orbits... Circular Orbit: _____ Elliptical Orbit: _____ Parabolic Orbit: _____ Hyperbolic Orbit: _____
Circular Orbit: e = 0 Elliptical Orbit: 0 < e < 1 Parabolic Orbit: e = 1 Hyperbolic Orbit: e > 1
Which frame of reference is used to describe orbits and define the Classical Orbital Elements (COEs)?
ECI
What does ECEF stand for?
Earth Centered Earth Fixed
What does ECI stand for?
Earth Centered Inertial
Earth Centered Inertial = _____ Earth Centered Earth Fixed = _____
Earth Centered Inertial = Non-Rotating Earth Centered Earth Fixed = Rotating
Which fundamental plane is Earth's orbit around the sun?
Ecliptic Plane Separated from the Equatorial plane by 23.5° due to the tilt of Earth's axis.
Which fundamental plane passes through the Earth's equator?
Equatorial Plane
Fill in what i's range is for the following orbits... Equatorial: _____ Polar Orbit: _____ Prograde Orbit: _____ Retrograde Orbit: _____
Equatorial: i = 0°, 180° Polar Orbit: i = 90° Prograde Orbit: 0° <= i < 90° Retrograde Orbit: i > 90°
True anomaly is the _____ of my satellite.
Location Measured from perigee → satellite location.
Are COEs always properly defined?
No. When e=0 (circular orbit, no perigee) or i =0 (equatorial orbit, no ascending/descending nodes) there are special COE calculations.
Which fundamental plane has the satellite's orbit?
Orbital Plane
What does RAAN stand for?
Right Ascension of the Ascending Node
Argument of perigee is the _____ of my orbit.
Rotation Measure from ascending node → perigee.
Eccentricity is the _____ of your orbit.
Shape "I can change my shape but not my size."
What are ground tracks?
The path a satellite travels relative to the Earth's surface.
Inclination is the _____ of your orbit.
Tilt Determines ascending and descending nodes.
RAAN is the _____ of my orbit.
Twist Measure from Vernal Equinox (1st point of Aries) → Ascending Node
What are TLEs?
Two-line element sets A data format used to keep track of a satellite's COEs.
What is the symbol for semi-major axis?
a
What is the symbol for eccentricity?
e
What is the symbol for inclination?
i
What is the symbol for true anomaly?
v
What is the symbol for RAAN?
Ω
