Editing Slow-scan television (section)

==History==

===Concept===
The concept of SSTV was introduced by Copthorne Macdonald<ref>{{Cite web|url=http://www.copmacdonald.com/|title=Copthorne Macdonald's Home Page|date=January 2, 2014|archive-url=https://web.archive.org/web/20140102230922/http://www.copmacdonald.com/|archive-date=2014-01-02}}</ref> in 1957&ndash;58.<ref name="Miller">{{cite web | url = http://www.darc.de/distrikte/g/T_ATV/sstv-history.htm | title = SSTV history | author = Miller, Don | access-date = May 9, 2006 }}</ref> He developed the first SSTV system using an electrostatic monitor and a [[video camera tube#Vidicon|vidicon tube]]. It was deemed sufficient to use 120 lines and about 120 pixels per line to transmit a black-and-white still picture within a 3&nbsp;kHz telephone channel. First live tests were performed on the 11-meter ham band{{snd}} which was later given to the [[Citizen's band radio|CB]] service in the US. In the 1970s, two forms of paper printout receivers were invented by [[Amateur radio operator|hams]].

===Early usage in space exploration===
[[File:S63-07856.jpg|thumb|Astronaut [[Gordon Cooper]], SSTV transmission from ''Faith 7'']]

SSTV was used to transmit images of the far side of the Moon from [[Luna 3]].<ref>[http://astrosurf.com/nunes/explor/explor_luna3.htm Luna 3<!-- Bot generated title -->]. {{webarchive|url=https://web.archive.org/web/20070929083752/http://astrosurf.com/nunes/explor/explor_luna3.htm |date=2007-09-29 }}.</ref>

The first space television system was called Seliger-Tral-D and was used aboard [[Vostok (spacecraft)|Vostok]]. Vostok was based on an earlier [[videophone]] project which used two cameras, with persistent LI-23 [[iconoscope]] tubes. Its output was 10 frames per second at 100 lines per frame video signal.

* The Seliger system was tested during the 1960 launches of the [[Vostok (spacecraft)|Vostok]] capsule, including [[Sputnik&nbsp;5]], containing the [[Soviet space dogs|space dogs]] [[Belka and Strelka]], whose images are often mistaken for the dog [[Laika]], and the 1961 flight of [[Yuri Gagarin]], the first man in space on [[Vostok&nbsp;1]].
* [[Vostok 2]] and thereafter used an improved 400-line television system referred to as Topaz. 
* A second generation system ([[Krechet]], incorporating docking views, overlay of docking data, etc.) was introduced after 1975.

A similar concept, also named ''SSTV'', was used on [[Mercury-Atlas 9|''Faith 7'']],<ref name="MercuryRadio">{{cite web |url=http://www.svengrahn.pp.se/radioind/Mercury/MercuryRadio.html |title=The Mercury-Atlas-9 slow-scan TV experiment |author=Sven Grahn |website=Space Radio Notes}}</ref> as well as on the early years of the [[NASA]] [[Project Apollo|Apollo]] program.
* The ''Faith 7'' camera transmitted one frame every two seconds, with a resolution of 320 lines.<ref name="MercuryRadio"/>
	
[[File:Apollo 11 first step.jpg|thumb|left|NASA slow-scan image from the Moon]]
The [[Apollo TV camera]]s used SSTV to transmit images from inside [[Apollo&nbsp;7]], [[Apollo&nbsp;8]], and [[Apollo&nbsp;9]], as well as the [[Apollo&nbsp;11]] [[Apollo Lunar Module|Lunar Module]] television from the [[Moon]]. NASA had taken all the original tapes and erased them for use on subsequent missions; however, the [[Apollo 11 missing tapes|Apollo&nbsp;11 Tape Search and Restoration Team]] formed in 2003 tracked down the highest-quality films among the converted recordings of the first broadcast, pieced together the best parts, then contracted a specialist [[film restoration]] company to enhance the degraded black-and-white film and convert it into [[Digital data|digital]] format for [[Archive|archival records]].<ref>{{cite web
|url= http://www.cosmosmagazine.com/news/3827/lost-apollo-tapes-restored-and-broadcast
|title= 'Lost' Apollo 11 Moonwalk tapes restored
|access-date= 4 November 2010
|author= Andrew Letten
|date= 2010-10-26
|publisher= [[Cosmos (magazine)|Cosmos Online]]
|url-status=dead
|archive-url=https://web.archive.org/web/20140720193330/http://cosmosmagazine.com/news/lost-apollo-tapes-restored-and-broadcast/
|archive-date=July 20, 2014
|quote= SYDNEY: After a three-year search for the lost Apollo&nbsp;11 tapes and an exhaustive six-year restoration project, digitally remastered footage of the historic Moonwalk is almost ready to be broadcast.
}}</ref> 
* The SSTV system used in [[NASA]]'s early Apollo missions transferred 10 frames per second with a resolution of 320 frame lines in order to use less bandwidth than a normal TV transmission.<ref>{{cite web |last1=Peltzer |first1=K.E. |title=Apollo Unified S-Band System |url=https://ntrs.nasa.gov/api/citations/19660018739/downloads/19660018739.pdf |archive-url=https://web.archive.org/web/20231206204415/https://ntrs.nasa.gov/api/citations/19660018739/downloads/19660018739.pdf |archive-date=6 December 2023 |date=April 1966 |url-status=live}}</ref>
* The early SSTV systems used by NASA differ significantly from the SSTV systems currently in use by amateur radio enthusiasts today.

===Progression===
Commercial systems started appearing in the United States in 1970, after the [[Federal Communications Commission|FCC]] had legalized the use of SSTV for [[Amateur radio licensing in the United States|advanced level]] amateur radio operators in 1968.

SSTV originally required quite a bit of specialized equipment. Usually there was a scanner or camera, a modem to create and receive the characteristic [[sound reproduction|audio]] howl, and a [[cathode-ray tube]] from a surplus [[radar]] set. The special cathode-ray tube would have "long persistence" [[phosphor]]s that would keep a picture visible for about ten seconds.

The [[modem]] would generate audio tones between 1,200 and 2,300&nbsp;Hz from picture signals, and picture signals from received audio tones. The audio would be attached to a radio [[receiver (radio)|receiver]] and [[transmitter]].