05 · Ground
Pass
From the ground: rise, race, set. A few minutes of sky. A dish that cannot slew is a GEO dish. A kit that hops birds is a LEO kit.
In English
On the ground you get a few minutes from rise to set. Higher means longer in the sky and a weaker signal. A LEO user terminal has to hop birds. A GEO dish points once.
- Try this
- Drag altitude. Horizon pass should stretch. Period too.
- Keep this
- A pass is minutes. The kit that tracks is the product.
Lab · a few minutes of sky
From the ground, a LEO sat rises, races, sets. Horizon to horizon is a slice of the period. Higher birds stay longer and look smaller. ISS is a bright four-minute streak if you know when to look.
Altitude 400 km
- Period
- 92.4 min
- Horizon pass
- 10.2 min
- Earth angular radius
- 20°
Horizon-to-horizon time ≈ T α / π with α = acos(R/r). Real passes are shorter because you need elevation above 10–25° for a usable link.
Ground tracks walk west because Earth turns under the inertial plane. ISS at 51.6° paints a band, not the poles. Polar SSO paints everything.