Observation 2400834: GRIFEX (40379)

Regarding Observation 2400834

This is weird - this observation has an unusually large number of data frames (302) - altho only 12 display in the dk3wn tlm decoder. Anyway, when I grab the IQ file from the pi gs 2400834.raw it is actually the iq for VZLUSAT1 2400835 cw !

The post obs scripts is just:

# cat /etc/default/satnogs-client
SATNOGS_POST_OBSERVATION_SCRIPT="/var/lib/satnogs/pos.sh {{ID}}"

# cat /var/lib/satnogs/pos.sh
/bin/mv /tmp/iq.raw /tmp/$1.raw

wonder why the one off. Ending timestamp on the web of 2400834 is 2020-06-18 15:07:43, for 2400835 is 2020-06-18 15:13:55 and the timestamp of 2400834.raw is (EDT) Jun 18 11:13 or 15:13Z which matches 2400835 exactly, and 6 minutes after 2400834. Somehow they got conflated in the temporal proximity and the grifex obs raw iq was lost :sunglasses:

Anyway - wonder about all the extra data. Looking at https://www.qsl.net/k/k4kdr//how-to/jpg-from-raw-data.pdf and the data there is an ffd8 start of image and ffd9 end of image

$ xxd -p grifex_2400834.kss | less
002900b7ff6f00bdffedffbf000d002000c500f9ffd800d80ad30a1d0bf6
0a030ce50baf0b9e0bc1000d0366023e00883388334c2000100000000000
d602000000000000ff723d00beffffffff670db0151c40c0c000968870a6

af03e81cbeafc28fb438a1363518708b5a7b13be1546bf3144d1a8d0298a
79a40097b559ade3688ab4ef72c674c3fe6e3df5fd927f0ec5cb0ae95729
ffd9f888e6d6a23d529c3f23a967f654f24075bf77bf495f032a3ac85085

Trying in a hex editor - there were interestingly 128 c0c000 kiss frames between those - but appearently not an actual image as it is full of invalid jpg ‘markers’ ffxx . Giving up.

Also - the data w/o kiss frames is 76502 bytes long, so by sheer statistics the words ‘ffd8’ and ‘ffd9’ have a good odds of appearing randomly :wink: I think any given 16bit word has an even chance of appearing in any randomly distributed series of 65536 16bit words.

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Maybe @jwc can shed some light on what’s going on.

Did a quick test with https://network.satnogs.org/observations/2411883/ ending 2020-06-20 13:24:42 and https://network.satnogs.org/observations/2411886/ starting 2020-06-20 13:24:46 - 4 seconds later, not quite overlapping (where you get the red box around the calculated timeline - I did not have that)

I ended up with a similar outcome as above with GRIFEX - a raw IQ file named 2411883.raw which should be Orbital Factory 2 with no signal, but actuall contains the IQ for 2411886 the FM Ham sat Saudisat 1C with lots of activity :sunglasses: There was nothing saved named 2411886.raw, two obs, one incorrectly labled file. The previous one 2410904.raw from 2020-06-20 13:08:18 to 2020-06-20 13:15:21 over nine minutes earlier is correct.

Guess I should file a bug and stare at the code - altho it’s pretty advanced python for me :grinning:

Hi, thanks for the tag. The original observation is a GRIFEX pass. Nice job decoding! We are downlinking archived data from the GRIFEX satellite. Beacons are mixed in, so you’ll see them every so often. Not as fast as every 10s because the data downlink drops the beacons sometimes.

Not sure about the mislabeling/tagging you’re seeing.