On Oct 27, 2023, at 7:21 PM, graham shirville via AMSAT-BB <amsat-bb@amsat.org> wrote:

Hi Sasha,

 

Thanks for the explanation…I had the same question my mind!

 

Just for the record, a 1U CubeSat, JY1SAT, also successfully used SSDV to downlink a number of preloaded images from Jordan.

 

As you can see it worked really well! http://sv2hwm.ddns.net/JY1SAT.php

 

The User Dashboard, based upon the FUNcube system, enabled one to “hole file” any missing blocks during subsequent orbits.

 

Sadly a failure in the onboard MCU some months ago means that it can no longer provide these images.

 

73

Graham G3VZV

 

 

From: Sasha Tim via AMSAT-BB <amsat-bb@amsat.org> 
Sent: Friday, October 27, 2023 2:58 PM
To: Zach Metzinger <zmetzing@pobox.com>; Amsat - BBs <amsat-bb@amsat.org>
Subject: [AMSAT-BB] Re: IO-117 status - we're back

 

Hi Zach,

 

The reason against JPEG is primarily because of the corruption capabilities. If the first packet is not received (which is often the case), the entire image will be corrupt. If a single packet is missed, it ruins the image for all of the packets after. 

 

Multiple satellites use raw JPEG in space currently, and it is not working well.'

 

A better format to use would be SSDV (https://github.com/fsphil/ssdv), which has been tested on HAB flights for a long time, and was originally implemented on an Atmega328! 

 

It retains the JPEG compression capabilities, while simultaneously protecting the imagery against potential packet loss. 

 

There were only three satellites that I know of that used SSDV in space, that is, GASPACS-1 and the Chinese Lunar Orbiter cubesats a while ago. 

 

On Thu, Oct 26, 2023 at 3:46 PM Zach Metzinger via AMSAT-BB <amsat-bb@amsat.org> wrote:

On 10/26/23 14:13, Sasha Tim via AMSAT-BB wrote:
> Any projects working on getting into MEO: PLEASE put in a camera (and 
> transmit in a format that is not JPEG)!

Hello Sasha,

Cameras do require a license, at least for the US. Not insurmountable, 
but one has to consider this aspect.

What's wrong with JPEG? You'd prefer GIF? (or TIFF?) :-)

--- Zach
N0ZGO

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