Still More on Long Round Trips
Intermittent connectivity – economic
- Very long distances.
- Signal strength attenuates as the square of distance.
- So the radio equipment used must be very powerful, hence very expensive, hence shared; connectivity must be episodic. So some loss of connectivity is inevitable.
- For example, the DSN may “track” a given spacecraft for only 2 hours per day – or only 8 hours once per week.
- Tracking station schedules change on a weekly or even daily basis. Advance prediction is challenging.
The combination of long signal propagation times and intermittent connectivity can make signal round-trip times very long and/or highly variable.