automatic picture transmission
From Glossary of Meteorology
(Abbreviated APT.) Low-resolution analog transmission of AVHRR data from polar orbiting satellites.
Two channels of reduced-resolution (4 km) data are continuously transmitted using analog VHF signals (137 MHz) at reduced rates (120 lines per minute), allowing use of simple, low-cost ground station equipment for APT reception. APT was initiated with the TIROS satellite launched in December 1963.
