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• 2.2 Automatic Picture Transmission

2.2 Automatic Picture Transmission¶

APT means Automatic Picture Transmission. It is a system, developed in the 1960s, made to transmit low-resolution analog image for weather satellites. A complete APT image takes around 12 minutes to be built up at a rate of 2 lines per second. The data is broadcasted by the satellite. The stream is obtained by the AVHRR/3 instrument. Two channels with a low resolution are emitting all the time using VHF signals at reduced rates (around 120 lines/minutes).
The two channels are composed of :

• A visible frequency range channel providing APT imagery during the day.
• An IR channel providing APT imagery at any time of the day and the night.