Re: Recovery mystery

Marty Griffin


This is brilliant!  Might send the trackers across the road to pick it up!

- Marty


From: <> On Behalf Of Jeff Deaton via Groups.Io
Sent: Wednesday, February 26, 2020 10:27 PM
Subject: Re: [GPSL] Recovery mystery


Hey John (KM6GKF),


I grabbed the packets from your flight off of and manually put them into the EOSS (Edge of Space Sciences) tracker software to see where it would plot a landing prediction.  This is what came out for coords:  37.09720, -120.30523.  This looks to be just short of a km East of the last position.  


Some screen shots:

There is some error here as I had to perform some “shenanigans” to get the system to process packets without a timestamp.

Granted, at this point it might be too little too late.  Sorry you lost ‘er.  :(



Jeff Deaton


On Feb 26, 2020, at 12:12 PM, Bill Brown via Groups.Io <wb8elk@...> wrote:

I always fly a SPOT Trace unit (and often fly two Trace units for redundancy) on my larger latex flights as a backup recovery unit. I recommend shaking it right before liftoff to make sure it starts up. I also highly recommend setting it up for the 24 hour status update which includes its current location coordinates. I have had one sitting on my desk for almost a whole year doing nothing but the 24 hour status transmission and the batteries are still good. The bad news for the SPOT units is that the altitude is not very accurate, if it is displayed at all, and the unit generally doesn't work above 40,000 feet but usually comes back to life below that altitude on the way back down. Not recommend for a primary or standalone tracker but it sure is a great backup recovery unit. 


On earlier models of the SPOT unit I have had them turn off by bouncing around inside a payload and hitting the buttons. I solved that by removing the rubber button assembly and just pushing on the metal snap button on the PC board before flight but so far have not seen the vacuum problem pulling in the button on the Trace unit. It is possible that on a very hard landing that the impact caused your Trace unit to reset and stop working.


I typically fly two APRS trackers, one Iridium tracker (my own design which has an onboard uBlox GPS and sensor) and one or two SPOT Trace units on a big flight particularly if there is a lot of expensive camera equipment onboard. The Iridium tracker sends an email with its location every 5 minutes and gives altitude and positions throughout the entire flight. I wrote a Python program to grab the data from the email and post it to APRS.FI to show up on the tracking maps. You can also send commands via email up to the Iridium tracker to turn things on/off or do a cutdown. 


The main message is to have triple or quadruple tracker redundancy to ensure recovery with a mix of ham radio and satellite modem trackers (Iridium or GlobalStar (SPOT)).


As to the GoPro camera, Make sure you have a large enough memory card to make it through a 3-hour mission. The Backup battery or an external power source is advised as well.  The recording mode makes a big difference too. If you are using 4K mode, you may not have enough memory card space or battery capacity to make it through a full mission and could also overheat.I have had good luck mounting the GoPro body through the styrofoam wall of a payload with a thin foamcore faceplate glued in place with holes for the button, light sensor and camera lens which are exposed to the elements. I haven't had one overheat in that arrangement.


- Bill WB8ELK





-----Original Message-----
From: James Ewen VE6SRV <ve6srv@...>
To: GPSL <>
Sent: Fri, Feb 21, 2020 12:58 pm
Subject: Re: [GPSL] Recovery mystery

I have not used the Spot Trace device, just relaying information that I have heard. No expectation of accuracy is to be assumed.


One of the first stories I read about using the Spot device talked about getting a good lat/long fix from the device, but upon arrival, there was no payload to be found. This baffled the recovery team until they noticed a cellular tower not too far away.


Their supposition was that the Spot device was giving them a location based on the tower, not an actual GPS reading from the device. There was also an instance where the Spot device stopped working on the way down. When they opened the battery case, there was a good suction "pop", and the unit began working. The device was assumed to have depressurized on the way up, but held the vacuum on the rapid descent. The membrane over the soft press buttons got pushed in by the higher external pressure, and the multiple button presses confused the device.


I'm pretty sure this was the same launch/recovery where these two stories came from. They fixed the vacuum issue by drilling a small hole in the case to allow it to vent. I can't recall how they managed to locate the package.


If the Spot device ends up upside down, I hear it might not get a GPS position as well.


Now, what about the APRS tracking you had on board? Did you listen for the transmissions on RF? You should have been able to hear them. From 4900 feet, the horizontal drift wouldn't be much. I would expect to find the payload north of Avenue 24, and south of Avenue 24 1/2. east of road 13, and west of road 14. Even if the GPS on the APRS payload couldn't get a fix, you should be able to track the payload transmitter using RDF techniques. Unless of course you have the payload configured to only transmit with a valid GPS lock.


Find someone with a drone, and have them fly over the suspected landing area with a camera on board. 


Whats' the last Spot location?




On Fri, Feb 21, 2020 at 8:09 AM John Kovac KM6GKF <jkovac@...> wrote:

We did a flight Tuesday in Northern California.   Followed it in flight and arrived at the landing location indicated by Spot Trace within a few minutes of landing.   But it wasn’t there.   Last APRS ping was at about 4900 ft and confirms same general landing area.

The Spot Trace has always led us directly to the exact landing site for all previous flights.  At this point we have searched a large area around the apparent landing site to no avail.   It is open farmland with few structures or people.   

As of right now, a few days post flight, there has been no ping from the Trace since the landing ping.   So that seems to indicate that no one has moved or taken it.  I stupidly did not set it up in advance to do a daily check in ping, so we are not going to get another ping until someone moves it unless the batteries die first, which Trace support guesses will be a few months.  And if that ping is in the same location we’ll still be baffled.

Any input greatly appreciated.


John Kovac

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