A spacecraft is 900000 km away. Use light speed 300000 km/s. Find one-way signal delay.
Answer and explanation
3 s
Delay=distance/speed=3 s.
Subjects
Space science
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Sample exercises
A spacecraft is 900000 km away. Use signal speed 300000 km/s and neglect processing delay. Find round-trip signal delay.
Answer and explanation
6 s
A round trip covers twice the one-way distance.
Which statement distinguishes data rate from signal speed?
- Data rate sets vacuum light speed
- They are always identical quantities
- Both are measured only in kilograms
- Data rate counts information per time; signal speed controls travel time
Answer and explanation
Data rate counts information per time; signal speed controls travel time
Bandwidth and propagation describe different aspects of communication.
An instrument uses 20 W for 15 s. Find energy consumed.
Answer and explanation
300 J
Energy=power×time.
Why can a spacecraft image not be interpreted fully without instrument metadata?
Answer and explanation
Exposure, wavelength band, calibration, geometry and processing can affect the signal. Metadata supplies the context needed to assess it.
Credit several measurement-context factors.
Which is an engineering tradeoff rather than a universal improvement?
- Communication has no delay
- Every orbit meets every goal
- All added hardware has zero cost
- More instrument capability may require more mass and power
Answer and explanation
More instrument capability may require more mass and power
Mission constraints must be balanced.
Study notes
Space missions, communications and measurement
A mission trades measurement goals against mass, power, thermal control, communications and trajectory constraints. No single orbit is best for every goal.
UniversitySpace missions, communications and measurement · revision notes
A mission trades measurement goals against mass, power, thermal control, communications and trajectory constraints. No single orbit is best for every goal.
UniversityOne-way signal delay
This exercise uses a constant distance and straight-line light travel, not a spacecraft maneuver model.
Grades 9–12One-way signal delay · formula reference
This exercise uses a constant distance and straight-line light travel, not a spacecraft maneuver model.
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