[A-DX] ===> "median stack" / Radio DARC / Technik-Ecke / APOLLO-TV

[Roger]

Am 03.08.2019 um 21:56 schrieb Roger:
>
> Sehr gut erklärt hier:
> https://patdavid.net/2013/05/noise-removal-in-photos-with-median_6.html


Heute gibt es bei Radio DARC in der Technik-Ecke Hintergrundinformationen
zu der TV-Übertragung bei der Apollo 11 - Mission.

https://www.darc.de/nachrichten/radio-darc/
Sendeplätze von RADIO DARC auf Kurzwelle:
     Jeden Sonntag 11:00 MESZ Hauptsendung auf KW 6070 kHz/100 kW + 7440
kHz/10 kW (für das Ausland)
     Jeden Montag  17:00 MESZ auf KW 6070 kHz/10 kW + 7440 KHz/10 kW
(für das Ausland)
     Täglich 17:00 MESZ auf 7440 kHZ / 10 kW (Für Asien/Australien)



In diesem Zusammenhang hatte ich selbst nach entsprechenden
Informationen gesucht und diese sehr interessante PDF gefunden:
https://www.hq.nasa.gov/alsj/ApolloTV-Acrobat5.pdf

Bei späteren Apollo-Missionen gab es dann einen Hinweis auf ein "Image
Transform System".
Das wurde zwar nicht exakt erklärt, hört sich nach "median stacking" an,
aber
ob man das "richtig digital" realisieren konnte?

PDF ab Seite 37:
"....In February of 1972, two months before the Apollo 16 launch, John
Lowry visited Col. James
McDivitt at MSC to show him the results of the Image Transform process.
John demonstrated
about two minutes of before and after processing of three scenes from
the Apollo 15 lunar video.
As a direct result of this demonstration Image Transform was contracted
to process and clean up
the lunar surface video for Apollo 16.
To add an effective 3db to 6 db improvement in video SNR the Apollo 16
video was routed from
Houston to Image Transform in North Hollywood for processing. This is
how the Image Transform
System worked:
Video noise is random from one frame to next. However, the static areas
of the images are largely
correlated frame-to-frame. By separating areas of motion from the static
portions of the picture, the
Image Transform System continuously combined four frames of video to
make each new frame.
38
In static regions of the pictures the noise was reduced by a factor of
four enabling significant enhancement
of the detail. The areas that were in motion were spatially filtered to
reduce the noise
a little, but did not impair the quality perception of the images
seriously due to the speed of the
motion. The spatially filtered static and temporally filtered motion
portions of the images were
recombined in such a manner as to leave few, if any, artifacts relating
to the images having been
processed.
The random video noise was quite obviously reduced, the images were
enhanced, and the final
broadcast pictures looked remarkably good. This process not only
improved the SNR of the low
light cameras and other noisy parts of camera chains but also cleaned up
the noise from the
Apollo color TV downlinks and microwave distribution paths...."


http://www.hawestv.com/moon_cam/moonctel.htm
"...Noise Reduction
Image Transform received a NASA contract to reduce noise in lunar video.
This extra processing smoothed and sharpened mooncam pictures during
Apollo 16 and 17. Image Transform was a North Hollywood, California
concern. In nearly real time, it polished video feeds from lunar surface
EVAs (extravehicular activities). After this processing, the video
returned to Houston for dissemination to worldwide TV networks."



roger