Math Problem Statement

a space exploration agency wants to place six satellites in orbit around a spherical moon so that a rover on the moon's surface can always transmit to at least one of them. if the radius of the moon is R, what is the minimum height above the surface of the moon at which satellites should be placed?

Solution

To solve this problem, we need to consider how the satellites are positioned in orbit and how they must be distributed so that a rover on the moon’s surface can always have line-of-sight communication with at least one satellite.

Since the moon is spherical, the satellites must be arranged in such a way that their coverage areas overlap sufficiently to ensure that the entire surface of the moon is covered.

Key Points:

  1. Number of Satellites: There are 6 satellites, and they need to cover the entire moon.
  2. Orbital Height: We need to find the minimum height hh above the surface of the moon where they should orbit.

Step-by-Step Solution:

1. Satellite Coverage:

Each satellite covers a circular area on the moon’s surface. To ensure that the entire surface is covered, we need to consider the angle of coverage for each satellite. The field of view of a satellite depends on its altitude hh above the surface.

  • Let the radius of the moon be RR.
  • The total radius from the moon’s center to the satellite would be R+hR + h.

The satellite's field of view (the area it can communicate with) on the moon's surface is related to the angle subtended by the arc it covers. The larger the altitude hh, the larger the satellite's field of view, but we want the minimum hh that guarantees coverage.

2. Geodesic Distribution:

To achieve complete coverage with 6 satellites, they should be distributed evenly around the moon, similar to how points are distributed on the surface of a regular polyhedron. A configuration that approximates this for 6 satellites is the vertices of an octahedron.

  • In this arrangement, the satellites will be located above the vertices of an octahedron, which has 6 vertices.
  • Each satellite will have to cover one-sixth of the moon’s surface.

3. Height Calculation:

The key is to ensure that the area covered by each satellite overlaps enough so that no part of the moon is left uncovered. This occurs when the horizon of each satellite reaches the boundary where the adjacent satellite's coverage starts.

From geometry, the angle θ\theta subtended by the satellite's horizon can be derived using the relationship:

cos(θ)=RR+h\cos(\theta) = \frac{R}{R+h}

Given that we need to cover the entire moon with 6 satellites, the angle θ\theta must satisfy:

θ=2π6=π3\theta = \frac{2\pi}{6} = \frac{\pi}{3}

Thus:

cos(π3)=RR+h\cos\left(\frac{\pi}{3}\right) = \frac{R}{R+h}

12=RR+h\frac{1}{2} = \frac{R}{R+h}

Solving for hh:

R+h=2RR + h = 2R

h=Rh = R

Conclusion:

The minimum height hh at which the satellites should be placed is equal to the radius of the moon RR. Therefore, the satellites should be placed at a height of RR above the moon’s surface.


Would you like more details on any specific part of this solution?

Here are 5 related questions to deepen your understanding:

  1. What are the implications of increasing the number of satellites for coverage?
  2. How would this problem change if the moon were not a perfect sphere?
  3. How would orbital mechanics influence the satellite height in real-world scenarios?
  4. Can this strategy be applied to cover other planetary bodies like Mars?
  5. How do signal delays impact communication with satellites in orbit?

Tip: When dealing with coverage problems, symmetry and geometric shapes like polyhedra can provide efficient solutions.

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Math Problem Analysis

Mathematical Concepts

Geometry
Spherical Geometry
Satellite Coverage
Geodesic Distribution

Formulas

cos(θ) = R / (R + h)
θ = π / 3

Theorems

Geometry of Spherical Coverage

Suitable Grade Level

Grades 10-12