Automatic Picture Transmission
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The Automatic Picture Transmission (APT) system on the National Oceanic and Atmospheric Administration (NOAA) satellites of the United States provides a reduced resolution data stream from the Advanced Very High Resolution Radiometer (AVHRR) instrument. It transmits the data continuously as an analogue broadcast that can be received in real-time by relatively unsophisticated, inexpensive ground station equipment while the satellite is within radio range. It was introduced in 1970 and for some three decades has provided image data to relatively low-cost user stations at locations in most countries of the world, giving many professional and other users their first introduction to real-time satellite imagery. A user station anywhere in the world can receive local data from up to three satellite overpasses twice a day from each satellite. Advances in communications technology will enable a transition to a new digital system - Low Rate Picture Transmission (LRPT) - in the early years of the new century.
