Abstract: A system and a method for the transmission and reception of digital data wirelessly using acoustic tones comprises an encoder, a data interleaving system, an error correction system, and a decoder. The digital data is decoded by using in-phase and quadrature filters and through a score based function that determines the data that was most likely transmitted.

Abstract: This disclosure presents a communication receiver system for spacecraft that includes an open loop receiver adapted to receive a communication signal. An ultrastable oscillator (USO) and a tone detector are connected to the open loop receiver. The open loop receiver translates the communication signal to an intermediate frequency signal using a highly stable reference frequency from the USO. The tone detector extracts commands from the communication signal by evaluating the difference between tones of the communication signal.

Abstract: Symbol synchronization in a continuous phase modulation receiver is achieved by calculating an arctangent function of a digital sample of the output of a quadrature demodulator. This signal is sampled by integration techniques or filtered to produce signals that represent a complex value whose phase changes at a rate which is half of the symbol rate. The complex value may be squared and rotated by an angle which is related to the symbol phase. The integrated sample or an arctangent function of the filtered sample is used as a controlling input for a numerically controlled oscillator which regulates the digital sampling.

Abstract: A method and apparatus are disclosed for making precise velocity measurements of a spacecraft using a two-way noncoherent Doppler tracking system. The received uplink and transmitted downlink frequencies on-board the spacecraft are compared with the resulting information being included in the downlink signal and used to cancel spacecraft oscillator drift rate effects in the two-way Doppler measurement made by the ground station. The information can also be used to characterize the drift rate of the spacecraft oscillator, thus permitting periods of accurate one-way Doppler tracking by the ground station. To improve accuracy, the times at which the measurements comprising the information would have been observed on the ground are inferred from the measurement of a signal generated by the spacecraft, e.g., the telemetry frame start times, made by the ground station.

Abstract: A method and apparatus are disclosed for making precise velocity measurements of a spacecraft using a two-way noncoherent Doppler tracking system. By comparing the received uplink and transmitted downlink frequencies on-board the spacecraft, information is generated that is included in the downlink signal and used to cancel spacecraft oscillator drift rate effects in the two-way Doppler measurement made by the ground station. This data can also be used to characterize the drift rate of the spacecraft oscillator, thus permitting periods of accurate one-way Doppler tracking by the ground station.