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CISSP 11.14 - Satellite Communications
This episode of the ISC2 Certified Information Systems Security Professional (CISSP) exam prep series looks up at satellite communications from Domain 4. It explains how orbits shape signal strength, latency, and coverage, so you can judge whether a link to space fits a use case and where its delay or exposure might undercut a design.
What this episode covers
- What satellite communications carry — radio waves relayed between the ground and a spacecraft, carrying phone, TV, radio, internet, and military traffic.
- The satellite as a relay — a mirror in the sky that catches a signal from one location and reflects it onward to another.
- The three main orbits — a low band near the surface, a middle band far higher, and a high band that keeps pace with the planet.
- The altitude trade-off — climbing higher widens each satellite’s footprint but weakens the signal and increases delay.
- Low orbit — a strong signal from a restless position that needs large constellations of satellites for steady coverage.
- Medium orbit — a wider footprint per spacecraft, paid for with a weaker signal and more delay.
- Geostationary orbit — a satellite that appears motionless, letting ground stations use fixed dishes but bringing the highest latency.
Watch the full episode above for the worked examples and step-by-step explanations of each concept.
Frequently Asked Questions
What are satellite communications, and what do they carry?
At heart they are radio waves bouncing between spots on the ground and a spacecraft circling above. That simple relay carries an enormous range of traffic, including telephone calls, television, radio, internet access, and military communication. The satellite acts as a mirror in the sky, catching a signal from one location and reflecting it onward to another far away.
What are the three main orbits a satellite can occupy?
Satellites sit in one of three altitude bands, and the band shapes everything about the link. There is a low band closest to the surface, a middle band far higher, and a high band far out where the satellite keeps pace with the planet. As you climb higher, the footprint each satellite covers grows, but the signal weakens and the delay increases.
What defines a low orbit satellite?
It flies closest to the ground, which gives it a strong signal but a restless position. Because it does not stay fixed over any one spot, you need many of them working together to hold steady coverage. This is why space-based internet services launch huge constellations of thousands of satellites, so that as one slips out of view another slides in behind it.
What changes with a medium orbit satellite?
It sits higher, so it lingers over a location longer than a low orbit satellite and covers a wider footprint from a single spacecraft. The cost of that height is a weaker signal and more delay, since the waves travel farther. It is a middle ground, trading some responsiveness for broader, steadier reach.
What makes a high, geostationary orbit special?
A satellite this far out circles the planet at exactly the speed the planet turns, so it appears to hang motionless above one fixed point. Ground stations do not have to track it across the sky and can simply aim a fixed dish and leave it. Its footprint is the largest of all, though its great distance brings the highest delay.
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Reference: This article is based on concepts discussed in CISSP 11.14 - Satellite Communications.