Latency
The time delay between transmitting a signal and receiving it, primarily determined by the distance a signal must travel at the speed of light.
Explanation
In satellite communications, latency is dominated by propagation delay. A signal traveling to a GEO satellite and back covers roughly 72,000 kilometers round trip, producing a minimum latency of about 240 milliseconds. In practice, processing and routing add more. For LEO satellites at 500 kilometers altitude, round-trip latency is roughly 5-10 milliseconds — comparable to terrestrial fiber. This latency difference drives the business case for LEO broadband constellations like Starlink, which compete with fiber and cable on speed, and dramatically outperform GEO for real-time applications like voice calls, gaming, and financial trading. Latency also matters for remote sensing: synthetic aperture radar processing, for instance, benefits from reduced downlink delay. For deep-space missions, latency becomes extreme — Mars rovers experience 5-20 minute one-way delays depending on planetary alignment.
Why It Matters
Latency is the decisive performance metric separating LEO and GEO communications. It determines what applications a satellite network can support and is the primary reason LEO constellations disrupted the satellite broadband market.
Concept Map
How Latency connects to other glossary terms:
Frequently Asked Questions
Is latency the same as bandwidth?
No. Latency is delay, measured in milliseconds. Bandwidth (or throughput) is data capacity, measured in Mbps or Gbps. They are related but different performance dimensions.
Why do GEO phones have noticeable lag?
The 240ms round-trip delay to GEO creates a half-second conversation lag that is noticeable in voice calls but acceptable for broadcast video.
Sources
Last updated: July 1, 2026