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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Automatic picture transmission | 2/2 | https://en.wikipedia.org/wiki/Automatic_picture_transmission | reference | science, encyclopedia | 2026-05-05T09:44:12.925851+00:00 | kb-cron |
=== Displaying the images === Years ago, to receive APT images, a specialized decoder was required in addition to the receiver to display or print images, much like HF WEFAX (serving the maritime community). Often both receiver and decoder were combined into one unit. Nowadays, with the advent of personal computers, all that is required is dedicated software such as WXtoIMG (many of which offer "free" versions [1]) and a sound card. The sound card acquires and digitizes the slow scan video (in the audible range) coming from the speaker, phones, or line-out of the receiver, and then the software will process the various visible and infrared channels of the AVHRR sensor.
==== Enhanced images ==== Since each channel of the AVHRR sensor is sensitive to only one wavelength of light, each of the two images is luminance only, also known as grayscale. However, different materials tend to emit or reflect with a consistent relative intensity. This has enabled the development of software that can apply a color palette to the images which simulates visible light coloring. If the decoding software knows exactly where the satellite was, it can also overlay outlines and boundaries to help in utilizing the resulting images.
== History == Developed by the National Earth Satellite Service Tested on TIROS-8, launched December 21, 1963 Nimbus 1, launched August 28, 1964, was the first application satellite First NOAA polar-orbiting vehicle to use it was TIROS-N, launched on October 13, 1978, and it has flown on all NOAA polar-orbiting vehicles since then. Also flown on the Soviet METEOR, Sich, Resurs and Okean weather satellites.
== Current status == There are currently no satellites that transmit APT. NOAA-15, the last satellite to transmit APT, was decommissioned on August 19, 2025. Previous satellites such as Sich-1 and the METEOR series of satellites operated on APT, but have since reached the end of their operational lifespans.
== Future == With improvements in electronics, analog transmission systems have given way to digital transmissions systems. NOAA-19, called NOAA-N' prior to its launch on 6 February 2009, is the last satellite to carry an APT system. The MetOp program, a collaboration between NOAA and EUMETSAT, as well as the Russian METEOR-M program have switched to Low Rate Picture Transmission (LRPT) for their new polar-orbit satellites. Since the NOAA-20 satellite, most of the NOAA satellites have their lowest transmission frequency at 7812 MHz in the C Band, making reception by the general public impractical since unlike older schemes (APT, LRPT) they require a dish antenna with a specialised antenna feed etc.
== See also == EUMETSAT Radiofax Weather satellites
== References ==
== External links == POES spacecraft status NOAA NEODAAS Dundee Satellite Receiving Station APT images received at Thirteen Island Lake Ontario Canada Decoding Software for APT Satellite Reception