Dynamic telemetry bit rates for deep space communications

A new telemetry playback scheme promises to maximize telemetry return for deep space missions. For a given effective isotropic radiated power from the spacecraft, the received signal-to-noise spectral density ratio and hence the supportable bit rate vary during a tracking pass as the elevation angle changes. In the past, spacecraft would use just one bit rate or perhaps a few different bit rates during a pass. However, large bit rate changes sometimes cause the ground receiver to go out of lock. The new scheme, which is examined here, allows the spacecraft to change its bit rate in frequent, small steps to match the signal-to-noise spectral density ratio profile. Because the rate changes are small, the ground receiver will be able to remain in lock