Compare low-orbit and geostationary satellite communication
Connect microwave links to the two listed satellite-phone arrangements and direct-broadcast television.
Section P3.3 · Electromagnetic spectrum
Exam scope and assessment notes
Mapped to the named 0973 section using teaching from the corresponding single-science course. A 0973-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade. This qualification reports two grades on the 9–1 scale; confirm the entry route for your zone and exam series.
Before you begin
- Explain electromagnetic vacuum propagation.
- Distinguish a microwave carrier from voice information.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which carrier is mainly used to communicate with artificial satellites?
What you will learn
- Identify microwaves as the main satellite communication carrier.
- Distinguish the listed low-orbit and geostationary uses.
Choose the correct satellite link
Communication with artificial satellites is mainly by microwaves. Some satellite phones use low-orbit satellites; others use geostationary satellites. Direct-broadcast satellite television uses geostationary satellites. The word 'satellite' alone does not identify the orbit type.
A geostationary satellite appears at a fixed position in the sky relative to a suitable ground location. A receiving television dish can point toward that direction. Low-orbit satellites change their apparent position, so systems use tracking, coverage changes or handover between links.
Separate orbit from propagation
Both arrangements use electromagnetic paths rather than sound crossing space. Orbit choice changes path length and coverage, not the common vacuum speed of a microwave. A longer path can add delay because the signal travels farther.
A diagram of ground → satellite → ground has two path segments. Do not replace the total communication path with satellite altitude or count only the upward segment. Real paths are slanted and real systems include processing; use a supplied ideal path only when stated.
Sources for this lesson
Pause and explain
Which orbit is used for the listed direct-broadcast satellite television arrangement?
Worked example
A direct-broadcast television dish points in a fixed direction toward a satellite. Identify the usual carrier and orbit type.
Show the worked solution
- The satellite communication carrier is mainly microwave.
- Direct-broadcast satellite television uses a geostationary satellite.
- Its fixed apparent direction supports the fixed pointing arrangement.
Answer Microwaves and a geostationary satellite.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Name the main region used for artificial-satellite communication.
Give me a hint
Identify the carrier, not the information content.
Compare my reasoning
- The route includes space.
- It uses electromagnetic radiation.
- The main listed region is microwaves.
Microwaves.
Look for these in your work
- Name the region.
- Keep voice separate from carrier.
List the two stated satellite-phone arrangements and the television orbit.
Give me a hint
Do not force all satellite applications into one orbit.
Compare my reasoning
- Some phones use low-orbit satellites.
- Some phones use geostationary satellites.
- Direct-broadcast satellite television uses geostationary satellites.
Phones: low orbit or geostationary; direct-broadcast TV: geostationary.
Look for these in your work
- Include both phone cases.
- Identify the television case.
An ideal relay has an upward path of 40 000 km and downward path of 38 000 km. What path length should a later delay calculation use?
Give me a hint
Add both stated travel segments.
Compare my reasoning
- The wave travels 40 000 km upward.
- It then travels 38 000 km downward.
- Total path = 78 000 km, not one altitude.
78 000 km total relay path.
Look for these in your work
- Count both legs.
- Do not infer an orbital altitude from the supplied path lengths.
Common mistakes
- Some satellite phones use each listed orbit type.
- Orbit does not change vacuum wave speed.
- A relay route includes both path segments.
What can you explain now?
Do all satellite phones use geostationary satellites?
Compare with the explanation
No.
Some use low-orbit satellites; some use geostationary satellites.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Describe satellite carriers, the two phone orbit arrangements and the direct-broadcast television orbit.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.