Decoding NOAA Satellite Images Using 50 Lines of Code
Decoding NOAA signals using SDR and Python
One of the interesting protocols developed in the last century is APT (Automatic Picture Transmission). It is used to transmit images of the Earth’s surface from space, and what is even more interesting for us, receiving APT signals is feasible for radio amateurs.
Let’s get into it!
General Information
The NOAA meteorological satellites, we’ll try to decode, belong to the TIROS (Television InfraRed Observation Satellite) series, the first of which was launched in 1960. There are currently 3 satellites in operation (NOAA-15, NOAA-18, and NOAA-19, the oldest of which, NOAA-15, works since 1998). The satellites orbit around the Earth at an altitude of about 850 km and make one revolution in about 1.5 hours. There are various sensors onboard, and we will be interested in receiving meteorological images. Here, there are two options available. The simplest way is to get an analog signal in the APT format at a frequency of 137 MHz. These satellites also transmit hi-res images in the HRPT (High-resolution Picture Transmission) format at a frequency of 1.7 GHz. HRPT decoders are also available, but a high-gain antenna and a special tracker are required, which is more difficult and expensive.
