Final answer:
The radii in the question refer to orbital distances for satellites, with 36,000 km being the most likely correct answer as it corresponds to the geosynchronous orbit at roughly 6 times the Earth's radius.
Step-by-step explanation:
The question refers to the separation an Earth Satellite Array (ESA) provides over certain radii during the last 45 years. These radii might refer to distances at which satellites have been placed in Earth's orbit. Here's a break down of the typical orbital distances and what they correspond to:
- 600 km: This is close to the Earth's radius, typical for satellites in Low Earth Orbit (LEO). Many Earth-observation satellites are positioned at this range.
- 6,000 km: While Earth's actual radius is approximately 6,371 km, this distance might refer to orbits just beyond LEO, but this isn't a standard orbital range.
- 36,000 km: This is roughly 6 times the Earth's radius and is the separation for geosynchronous orbits. Satellites here orbit at a speed matching the Earth's rotation, appearing stationary from the ground.
- 385,000 km: This distance is roughly the separation between Earth and the Moon, but it is not a typical orbit for Earth satellites.
- Beyond the distance to the moon: Satellites or probes sent further than the Moon are typically in interplanetary space or on a trajectory to leave the Earth-Moon system.
Considering the options provided, 36,000 km seems the most likely correct answer, as this is a well-known orbital distance for geosynchronous satellites. The mention of 'about 6 R°' supports this, indicating a distance of approximately 6 Earth radii, which is typical for geosynchronous orbits.