[amsat-bb] Re: Digital Slow Scan in space
g0mrf at aol.com
g0mrf at aol.com
Fri Sep 7 15:05:39 PDT 2012
I believe the digital SSTV that is used on HF / VHF is in reality DRM,
which is a forward error corrected digital communications standard (?)
I suppose the real difficulty is implementing a method of reading an
image file and then encoding it for transmission in a broadcast type
format for general reception rather than one that requires handshaking
or acknowledgments from the groundstation.
An essential feature would be that whenever a 'packet' of data is
received, that data is displayed rather than waiting for the complete
image to be received error free.
I couldn't find much on DRM encoding but I think it was originally
intended for digital voice in a narrow bandwidth so it sounds suitable
for low power satellite use.
From: Simon HB9DRV <simon at hb9drv.ch>
To: 'Graham Shirville' <g.shirville at btinternet.com>; 'AMSAT BB'
<amsat-bb at amsat.org>
Sent: Fri, 7 Sep 2012 21:51
Subject: [amsat-bb] Re: Fw: Digital Slow Scan in space
Well you should be able to do it on small ARM processor, but you've
got to take transmission time into account - those pesky satellites do
to move about quite a bit :)
There's also the format used by the NOAA weather satellites - simple and
Simon Brown, HB9DRV
From: Graham Shirville [mailto:g.shirville at btinternet.com]
Good question - "medium" was a deliberately vague term as it will also
depend on the camera and available data rates etc.
I was hoping we might be able to move on from analogue SSTV now.. we
be able to achieve much better quality images,,,as you suggest the
would be to do the digital encoding on board the spacecraft without
lots of power but, as mentioned, - if they can do it on a tiny payload
hanging beneath a small helium balloon then it should be possible to do
something similar on a spacecraft even a 1U cubesat!
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