Visibility Window Demo
Explore how the half-window ψ limits the relative longitude interval where a satellite is visible above a minimum elevation angle.
Visibility window demo
The satellite is visible while the relative longitude stays between -ψ and +ψ.
The full visibility window is therefore 2ψ.
Animation speed
Minimum elevation
Half-window ψ
Window 2ψ
Visible time
Interpretation
Δλ is the longitude difference between the satellite and the ground station, measured along the equatorial plane.
When Δλ = 0, both have the same longitude.
The satellite is visible while |Δλ| ≤ ψ.
Higher orbit radius → larger ψ → wider visibility window.
Smaller relative angular speed → longer time spent inside that window.
What the animation shows
• The satellite is visible when its relative longitude stays inside the shaded arc.
• The boundary points are at -ψ and +ψ.
• The full angular visibility window is 2ψ.
• Δλ is the current longitude difference between the satellite and the ground station, measured along the equatorial plane.
• ε is the elevation angle between the local tangent at G and the line of sight GS.
• The visibility time is tvis = 2ψ / ωrel.