Pegasus VII

After 18 months thought it would be cool to resurrect my last remaining gumstix and rebuild the SSTV payload. Pegasus VI was a great flight, watching the images come through was great fun - with the more recent developments in UK HABing it should be even easier to track and with the potential for multiple listeners should be able to get some great pictures. On Pegasus VI I used a Canon A60 over USB - this is quite a large camera and the interface over usb was a challenge so this time I'm going to use a serial jpeg camera. These cameras are actually becoming quite rare as the chipset has been discontinued so I snapped one up from Active Robots.

• Gumstix Verdex - got
• GPSstix daughter board - got
• C328 Jpeg Serial Camera - got
• Radiometrix NTX2 - got
• USB Mass Storage Device - got

1. First step was to check that the gumstix still worked - using my mm232r usb-serial adapter I was easily able to log into the gumstix - everything was still functioning well.
2. Rebuilt my gumstix build environment using the most up to date svn copy - took 3 days to actually get working. My first approach was to use virtualbox on my Mac however this was slow and there were far to many patches to manually add. I finally resorted to rebuilding my linux server and compiling on there - that still took a day to compile!
   1. As I ended up using ubuntu to compile the build environment this required me to change /bin/sh to use bash rather than dash. To change this you need to run:

      sudo dpkg-reconfigure dash

      and select “No” - best to do this before compiling the build environment.

   2. Also worth install TCL as well before you start as this will avoid sqlite errors

      sudo apt-get install tcl

   3. The required manual patches can be found at Labbook.
3. Reflashed the gumstix with the latest image compiled in my build environment using this guide off the gumstix wiki
4. Once setup I then compiled python for the the gumstix, to get the camera working I found that I needed:
   • python-core
   • python-fcntl
   • python-io (I forced this installation using -nodeps)
   • python-math
   • python-re
   • python-oldstring
   • python-pyserial
   • python-codecs
5. With python installed I was able to rig up the camera via a breadboard and grab the images using the script from the Sparkfun Forums. Some adjustments to the script then set it up to loop and save the images to a usb memory stick.
6. Interface Radio to gumstix via audio out
7. Recompile latest SSTV code - sstv.zip
8. Interface camera to the SSTV code
9. During the gaps when the image is being processed and encoded I now have setup the gumstix to transmit rtty following the UKHAS standard to allow for tracking on spacenear.us. Currently it tx's 6 rtty strings for every SSTV image.
10. Added gps parsing code using python - reminds me of why I like high level languages - being able to just split strings and then easily do the conversion to decimal degrees. Also set it up to log to the memory stick.
11. Wrote (and borrowed) code to generate checksums so now transmitted RTTY is now XOR checksum'd.
12. First using pamflip, flip the image as camera is setup upside down. Then using the ppmlabel function of netpbm have now overlaid the gps location data over the SSTV images, after the last flight it was suggested that purple might be the best colour. The overlaying doesn't affect the initial picture which is saved to the memory stick.
13. Secure verdex to daughterboard - instead of nuts, washers and bolts I've used carefully placed elastic bands which hold it securely in place.

1. Turn on payload
2. Check for GPS lock and Images
3. Check focus of camera
4. Seal payload
5. Attach to Flight Train
6. Launch!

• Pegasus VII is transmitting both RTTY (50 baud, 425 shift, ascii-8, no parity, 1.5 stop - select pegvii in dl-fldigi) and SSTV images (Martin 1).
• There are a number of programs available to decode SSTV images off the radio:
  • MMSSTV on Windows
  • Multiscan on Mac OSX
  • Qsstv on Linux
• It should be possible to run both dl-fldigi and a SSTV decoder at the same time. Currently I'm running dl-fldigi setup to decode the RTTY and then MMSSTV (in Wine) in the background, MMSSTV is excellent as it is able to automatically recognise the SSTV signal and start decoding and will save it.
• If you want help setting up a SSTV decoder get in touch on irc.freenode.net #highaltitude
• Using uploadr.py I monitor MMSSTV's history file and automatically upload any new images that are decoded to my flickr photostream.

Success

Pegasus VII was launched at the bottom of a flight train on 17/06/10 from Churchill College, Cambridge, ascended to 16.8km and then descended by parachute and was recovered from a hedge near Bedford. The flight was a great success with the payload working really well, transmitting images which were clearly received from Cambridge but also Bicester and Middlesborough. The payload was recovered intact and is ready to fly again.

More info can be found on the UKHAS wiki flight page: Nova18 and Peg VII

• Stop transmitting images on descent below 2km as you risk losing telemetry to help recovery.
• Add a temperature sensor as it got quite hot on the ground.
• Fix uploading of images to spacenear.us
• Use a smaller memory stick as 1 flight took up 1.8Mb out of 4Gb

• http://diydrones.com/profiles/blogs/secrets-of-the-c328
• http://forum.sparkfun.com/viewtopic.php?t=17119
• http://gizmologi.st/2009/04/taking-pictures-with-arduino/
• http://www.sparkfun.com/commerce/product_info.php?products_id=9334
• http://www.mail-archive.com/openembedded-users@lists.openembedded.org/msg00586.html
• http://www.active-robots.com/products/sensors/sparkfun/jpeg-colour-camera-uart-interface.shtml
• http://psurobotics.org/wiki/index.php?title=Building_Gumstix-OE_on_Fedora_11#unifdef
• http://www.gumstix.net/Setup-and-Programming/view/Getting-started/Setting-up-a-build-environment/111.html
• http://jarv.org/sdcam.shtml