Unit 2.4 COE

Question 1

𝑎

Answer 1

Semi major axis
Describes - size of the orbit
Range - 0 to infinity
Measured from: Perigee
To: halfway to apogee

Question 2

𝑒

Answer 2

Eccentricity
Describes - Shape of the orbit
Range - 0 to infinity
𝑒=0: Circular Orbit
01: Hyperbolic Orbit

Question 3

𝑖

Answer 3

Inclination
Describes - tilt of the orbit
Range - 0 to 180
Measured from: K vector/equatorial plane
To: H vector/orbital plane
 Equatorial: 0, 180
 Polar Orbit: 90
 Prograde Orbit: 0 - 90
 Retrograde Orbit:90 - 180

Question 4

Ω

Answer 4

Right Ascension of the Ascending Node (RAAN)
Describes: Twist of the orbit
Range - 0 to 360
Measured from: Vernal Equinox
To: Ascending node

Question 5

𝜔

Answer 5

Argument of Perigee
Describes: orbit rotation
Range - 0 - 360
Measured from: Ascending Node
To: Perigee

Question 6

𝜈

Answer 6

True Anomaly
Describes - satellite location
Range - 0 - 360
Measured from: Perigee
To: Satellite

Question 7

When 𝑒=0

Answer 7

There is no perigee, thus 𝜔 and 𝜈 are undefined
Use argument of latitude, 𝑢, measured from ascending node to spacecraft’s position vector, 𝑟⃗, in the direction of the spacecraft’s motion

Question 8

When 𝑖=0

Answer 8

There is no ascending node, thus Ω, and 𝜔 are undefined
Use Longitude of perigee, Π, measured from the principal direction, 𝐼̂, to perigee, 𝑒⃗, in the direction of the spacecraft’s motion

Question 9

When 𝑒=0 and 𝑖=0

Answer 9

There is no perigee or ascending node, thus Ω, 𝜔, and 𝜈 are undefined
Use True longitude, 𝑙, measured from the principal direction, 𝐼̂, to the spacecraft’s position vector, 𝑟⃗, in the direction of the spacecraft’s motion

Question 10

TLE

Answer 10

Two-Line Element. Used to quantify satellite position, velocity, orbital perturbations showing all 6 orbital elements (mean anomaly instead of true anomaly) and values quantifying expected drag of a satellite

Question 11

Orbital Propagation

Answer 11

Prediction of the orbital characteristics of a satellite at some future date given the current orbital characteristics