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@hb9drv.ch To: 'Graham Shirville' g.shirville@btinternet.com; 'AMSAT BB' amsat-bb@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@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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