Latency

The delay between sending a signal and receiving the reply, set mostly by how far the signal has to travel.

Why it matters

Latency is the number that decides what a satellite link can be used for, and it follows directly from orbital altitude. A round trip to geostationary altitude and back covers about 143,000 km, which adds roughly a quarter of a second no matter how good the hardware is - fine for broadcast, unusable for a video call or a trading system. From low orbit the round trip is a few dozen milliseconds. That single physical fact, not technology, is why broadband constellations moved down.

In our data

The trade-off is visible in where things actually go: 144 of the 350 missions we track head for low Earth orbit, against 23 bound for geostationary transfer orbit. The industry has voted for latency over coverage per satellite, and accepted needing far more spacecraft as the price.

Where we use it

Not to be confused with

Bandwidth, which is how much data a link can carry rather than how fast it starts arriving. A link can have enormous bandwidth and still feel slow, which is exactly the geostationary case.