derive an expression for the total energy of a satellite orbiting the earth. What is the significance of negative total energy?

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Now significance of this negative energy is , when a satellite is revolving around the earth then due to friction with the atmosphere of the earth or due to the collisions with the meteors in the space the total energy$\left(-\frac{GMm}{2r}\right)$ reduces so the $\left(\frac{GMm}{2r}\right)$ is increasing .Resultanly the value of r is decreasing .So the satellite is coming close to the earth .So from the surface of the earth as the distance of the satellite decreases the orbital velocity and kinetic energy increases though the total energy of the satellite decreases .

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