[amsat-bb] Re: Digital Slow Scan in space

[g0mrf at aol.com]

Hi both.

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.

Thanks

David



-----Original Message-----
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 
always
got to take transmission time into account - those pesky satellites do 
tend
to move about quite a bit :)

There's also the format used by the NOAA weather satellites - simple and
works...

Simon Brown, HB9DRV
http://sdr-radio.com


-----Original Message-----
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 
should
be able to achieve much better quality images,,,as you suggest the 
challenge
would be to do the digital encoding on board the spacecraft without 
using
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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