Orbital Mechanics & Spacecraft Operations Flashcards

What is Kepler's third law's relationship between orbital period and semi-major axis?

Answer: Period squared is proportional to the cube of the semi-major axis

Kepler's third law states that T² ∝ a³, meaning the square of the orbital period is proportional to the cube of the semi-major axis, a fundamental relationship in orbital mechanics.

What is delta-v (Δv) in the context of spacecraft orbital maneuvers?

Answer: The change in velocity required to perform an orbital maneuver

Delta-v represents the change in velocity a spacecraft must achieve to perform a maneuver, and it directly determines the propellant required via the Tsiolkovsky rocket equation.

What is the primary advantage of a Medium Earth Orbit (MEO) for navigation satellite constellations like GPS?

Answer: Global coverage with fewer satellites than LEO while avoiding GEO latency

MEO (~20,200 km for GPS) provides wide coverage footprints requiring fewer satellites for global coverage than LEO, while offering significantly lower latency than GEO for precision timing.

What is orbital inclination drift in GEO satellites caused by?

Answer: Gravitational perturbations primarily from the Moon and Sun

Lunar and solar gravitational forces exert out-of-plane perturbations on GEO satellites, causing inclination to increase by about 0.75° per year if uncorrected.

Which spacecraft attitude control method uses the interaction of a magnetic coil with Earth's magnetic field?

Answer: Magnetorquer (torque rod) control

Magnetorquers generate torques by running current through coils, interacting with Earth's magnetic field to control satellite attitude without expending propellant.

What is the purpose of the argument of perigee in describing a satellite's orbit?

Answer: It specifies the angle between the ascending node and the perigee point within the orbital plane

The argument of perigee is the angle measured in the orbital plane from the ascending node to the perigee, defining the orientation of the ellipse within its plane.

What is a frozen orbit and why is it used in satellite operations?

Answer: An orbit with carefully chosen elements so eccentricity and argument of perigee remain nearly constant over time

A frozen orbit has its eccentricity and argument of perigee chosen so that perturbations cancel out, keeping the orbit stable and maintaining a consistent altitude over the ground.