Algorithms for Synchronization of the Weather Satellites Automatic Picture Transmissions

The Automatic Picture Transmission (APT) system was used on the first weather satellites to send analog images. Even though it has been replaced by digital satellite transmission systems like High Resolution Picture Transmission (HRPT), many enthusiasts still use APT transmissions with simple receiver equipment to get satellite pictures. However, synchronizing APT images using the synchronization sequences designed for analog television can be difficult when transmissions are affected by noise. This paper proposes a strong synchronization method for noisy APT pictures. It also proposes a solution for estimating the Signal-to-Noise Ratio (SNR) and using the estimated SNR for synchronization correction. The proposed synchronization methods were tested using computer simulations and processing APT images received using an SDR platform.