National Oceanic and Atmospheric Administration (NOAA)
Weather Satellite Automatic Picture Transmission (APT)

NOAA-15 APT 2016-01-17 0151 UTC

NOAA-15 satellite APT 2016-01-17 0151 UTC

NOAA APT 2016-01-17 1444 UTC

NOAA-18 satellite APT 2016-01-17 1444 UTC

The above NOAA weather satellite automatic picture transmission (APT) images show a low pressure area off the west coast of North America on January 17, 2016. The coast line is the green line on the right side of the image and the yellow lines are the USA states and Canada provinces. The red lines are the latitude and longitude lines.

The left image was taken at 0151 UTC and the right image was taken about 13 hours later at 1444 UTC. The low pressure area moved northeast during this time.

In the northern hemisphere winds rotate counter-clock wise around the low pressure area as shown by the pattern of the white clouds. A good example of a low pressure moving across the UK is shown in the YouTube video by Met Office.

The NOAA-15, NOAA-18 and NOAA-19 are Polar-orbiting Operational Environmental Satellites (POES) in low Earth orbits (LOE) that are Sun-synchronous orbits. Their APT is continuously transmitted on 136.1 MHz or 136.9125 MHz. The signal is an analog signal consisting of an amplitude-modulated 2400-Hz subcarrier frequency modulating the RF carrier. The FM modulation is 30 kHz wide which prevents narrow FM modulation receivers from being used. Based on the SDR spectrum the receiver bandwidth is set to 50 kHz to receive all the sidebands of the modulated signal. The NOAA-19 APT image resolution is 4-km (2.5-mi).

Two POES observe every part of the Earth at least twice every 12 hours. POES deliver meteorological data free of charge to users worldwide. NOAA satellites are responsible for daytime afternoon orbits.

The NOAA-15 satellite image and NOAA-18 satellite image were received with an Airspy software define radio (SDR) receiver and the image decode was done with WXtoImg software.


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