When a satellite moves from a higher orbit to a lower orbit, what happens to its gravitational potential energy, kinetic energy, and total energy?

The gravitational potential energy of a satellite in orbit is given by $U_g = -\frac{GMm}{r}$, where $G$ is the gravitational constant, $M$ is the mass of the central body, $m$ is the mass of the satellite, and $r$ is the orbital radius.
As the satellite moves from a higher orbit to a lower orbit, the orbital radius $r$ decreases. Since $U_g$ is negative and $r$ decreases, the potential energy becomes more negative, which means the gravitational potential energy decreases.

For a satellite in a stable circular orbit, the kinetic energy is given by $K = \frac{1}{2}mv^2$. The orbital speed $v$ is related to the orbital radius by $v = \sqrt{\frac{GM}{r}}$.
Substituting this into the kinetic energy formula:

As the satellite moves from a higher orbit to a lower orbit, $r$ decreases. Therefore, the kinetic energy $K$ increases.

The total energy of the satellite is the sum of its kinetic and gravitational potential energy:

As the satellite moves from a higher orbit to a lower orbit, $r$ decreases. Since $E$ is negative and $r$ decreases, the total energy becomes more negative, which means the total energy decreases.

Comparing these changes with the given options:

• Kinetic energy: increases
• Gravitational potential energy: decreases
• Total energy: decreases

This matches option C.

The final answer is $\text{C}$.