Saturday, March 22, 2008

SDG-9 - nothing yet from Newfoundland

Dan, VO1MX, reports nothing heard so far in Newfoundland. Not necessarily bad news, since the balloon would have been almost 200 miles from Dan when he started listening and he reported S7-8 noise on the frequency. So it could be there and simply too weak for him to hear.

If anyone in Newfoundland is reading this right now, please listen to 29.499 Mhz right now and see if you can hear the beacon! Even if it is there right now, it will be moving very fast and the chance to hear it will be quickly over.

Thanks to all who have written and asked about it... We remain hopeful and welcome any reports.

Possible SDG-9 trajectories

Here are three possible trajectories for SDG-9 as of 1900z today. It should be audible in Newfoundland right now if it is flying at 9-10km, otherwise it is unlikely to be heard by anyone for a while.

Beacon details for SDG-9

The beacon is transmitting the following string on 29.499 Mhz using conventional CW:


Where the number following "F" is the frame counter, incrementing with each transmission, and the number following "A" is a numeric code representing temperature. Below is a table of numeric values and associated temperatures in Celsius.


Note that both the "A" value and the frequency of the beacon will drift significantly downward after local sunset for the balloon.

SDG-9 update

Tom, WB2YDS, is on Long Island and copied a good deal of telemetry last night before the balloon went over his horizon. Sunset was clearly visible in the data, as the internal temperature plummeted and the frequency of the transmitter drifted downward. The temperatures copied by Tom ranged from -9C at 2138z, down to -41C at 2322z.

The last two strings that he copied (at 2314z and 2322z) seemed to show the temperature leveling off at around -40C, which would indicate a float about 2km lower than the designed float altitude. If this is indeed the case, then we could have some problems - 2km lower means that we will run into a good deal more moisture on our northern voyage and possibly pick up ice. Just a bit lower yet - at around 7.5km in altitude - the entire trajectory changes and the balloon ends up floating aimlessly in the doldrums.

On the other hand, Pierre, KA2QPG, the designer of the beacon and my cohort in this endeavour, points out that the beacon itself gives off about 100mW of heat and could be skewing the internal temperature a bit. If so, then we could still be at 9-10km and heading in the right direction. We'll see.

At around 1800z today, *if* the balloon is on the right trajectory, it should be passing Newfoundland at about two hundred miles off the east coast. I've alerted some amateur radio ops in NL and they will be listening!

Friday, March 21, 2008

SDG-9 Update

Bob Bruninga has lost the signal as of 1753 EDT. Tom, WB2YDS, reported copying the signal at 1738 EDT on Long Island. Still analyzing the data from both - if you have any further data, please send it our way!

Below is a link to a short YouTube video of the balloon and payload shortly after launch. Sorry, no better pics or video of the actual launch are extant (my 12 year old son and I were a little busy with the launch itself - I pulled the camera out of my pocket as soon as I could!).
Update: Bob Bruninga, the father of APRS, is hearing the beacon in Annapolis!

Now if the balloon can survive sundown in a few hours (were those pinholes sealed or not?!), perhaps we can look forward to the 48 hour flight projection shown below... Any listeners to the north?

SDG-9 projected flight path after reaching stable float at 10km - note that the times are about 30 minutes behind real-time: