Satellite Geodesy part 3

What equation relates propagation velocity, wavelength, and frequency?

v = λf.

What does λ represent, and what is its SI unit?

Wavelength; metres (m).

What does f represent, and what is its SI unit?

Frequency; hertz (Hz), equivalent to oscillations per second.

What does v represent, and what is its SI unit?

Propagation velocity; metres per second (m/s).

What type of waves does satellite navigation use?

Electromagnetic waves.

What equations describe the characteristics of electromagnetic waves?

Maxwell’s equations.

What generates electromagnetic waves, according to the answer key?

Oscillating electric or magnetic forces.

What two fields propagate together in an electromagnetic wave?

An electric field and a magnetic field.

What is the period of a periodic wave?

The time required for the disturbance to repeat at a fixed point.

What is the wavelength of a periodic wave?

The distance over which the disturbance repeats at a fixed time.

What equation relates frequency and period?

f = 1/P, where P is the period.

How can the period be calculated from frequency?

P = 1/f.

What is circular frequency also called in the reviewer?

Angular velocity.

What equation defines circular frequency?

ω = 2πf.

What symbol represents circular frequency?

ω (omega).

What is a sinusoidal wave?

A periodic wave that can be modelled by a sinusoidal function in space and time.

What equation describes a sinusoidal disturbance using phase measured in cycles?

y(t) = A sin[2π(t/P + Φ₀)].

In the sinusoidal-wave equation, what does y(t) represent?

The magnitude of the disturbance at time t.

In the sinusoidal-wave equation, what does A represent?

The amplitude, or maximum magnitude, of the disturbance.

What does Φ₀ represent in the sinusoidal-wave equation?

The initial phase at t = 0, measured in cycles.

What equation gives phase in cycles when an initial phase is included?

Φ(t) = t/P + Φ₀ = ft + Φ₀.

What is the relationship between phase angle in radians and phase in cycles?

ϕ = 2πΦ.

How many radians correspond to one complete cycle?

2π radians.

What equation describes a sinusoidal wave using angular frequency and an initial phase angle?

y(t) = A sin(ωt + ϕ₀), where ϕ₀ is the initial phase angle in radians.

What describes the current state of a periodic wave at a particular time?

Its phase angle, or phase.

For zero initial phase, what equation gives phase angle in radians?

ϕ = ωt.

For zero initial phase, what equation gives phase in cycles?

Φ = ft.

What equation relates frequency to the rate of change of phase in cycles?

f = dΦ/dt.

How is phase in cycles expressed when propagation range is included?

Φ = ft − ρ/λ, where ρ is the range between emitter and receiver.

What does ρ/λ represent in the phase equation?

The propagation range expressed as a number of wavelengths, or cycles.

What electromagnetic-wave property describes the orientation behaviour of the electric field?

Polarization.

What is linear polarization?

The electric field oscillates along a fixed orientation in space.

What is circular polarization?

The electric-field vector rotates, tracing a circle in the plane perpendicular to propagation.

What type of polarization is mainly used for signals in satellite geodesy, according to the reviewer?

Circular polarization.

What two reasons does the reviewer give for using circularly polarized satellite signals?

The satellite’s orbital motion and Faraday rotation of the polarization plane.

What is Faraday rotation in the context of satellite signals?

Rotation of the plane of polarization associated with propagation through the upper atmosphere in Earth’s magnetic field.