WX Sonde Chase Redux

It’s been a couple weeks since my last effort in tracking and retrieving a weather sonde; luckily, this time the predicted landing sites don’t include any islands or water bodies. For this trip not only is there r00t providing realtime prediction updates and navigation but also Murthy, who is handling electronic communications and photography. I will be handling the driving and any necessary tree climbing, swimming, hiking or running.

The extensive pre-flight predictions showed the most likely landing area to be on the western side of Mt. Vaca ridge line, just east of Napa Valley. We slowly made our way to a predefined GPS location to start the monitoring. We were very lucky to get a cellular signal from this location as we had no signal for 30 minutes leading up to this location.

This is our pre-defined tracking location just east of Napa Valley.

Upon setting up, turning on the receiver and establishing communications with r00t, we were informed that the GPS data coming from the USA-Satcom sonde monitoring station (in Sacramento, CA) was indicating that our sonde was not following the predicted path! We were out of position and so had to quickly move back into the valley east of Mt. Vaca.

Once we moved and re-established communications with r00t we were able to properly track the sonde to the landing site. r00t provided realtime navigation so precisely it was scary. He even was able to give us alternative routes to avoid traffic congestion (and missed exits due to police car in next lane).

The red line in the Google Earth screenshot below shows the path of the sonde from the time when we turned on our mobile tracking system to the landing site (valley floor quite west of Mt. Vaca near Winter’s CA). The path of our vehicle is shown in yellow. All the data is coming from the mobile tracking system.

Overall path of sonde (red) and path of vehicle (yellow).

The screen shot below shows the exciting last few minutes of the sonde path as we try to navigate as closely as possible.

Final path of sonde (red) and path of vehicle (yellow).

Finally, it lands! And we are nearby… The screen shot below is from r00t; he is using the GPS location data from the sonde that we are relaying to him along with our position.

The final descent of the sonde and ultimately the recovery.

The recovery took some time, but you can see in the image above that ultimately the sonde was recovered and made it’s way back to the truck (still transmitting until the battery was disconnected).

Here is the view of the landing area, yes, it’s an orchard of walnut trees. But this is much better than a lake or island.

Walnut tree orchard.

Even though we have the location of the sonde, we must still find it, as it didn’t land on the ground. The last location shows that it is 14 meters above the ground (in a walnut tree). So now begins the search…

I gathered my gear and head into the walnut orchard.

We used small portable radio with log periodic antenna to locate the precise tree. The image below is the zoomed in view of the orange parachute that slowed the sonde as it traveled back to earth. The parachute is at the top of the tree which is 14 meters.

Sonde parachute atop a walnut tree.

It was a bit tricky to get down. The sonde is actually attached to the parachute via a line about 30 meters from this location on another tree top. We borrowed a 15 foot ladder from the land owner to gain access to a large tree branch, but then still had to use a 15 foot PVC extension pole with a hook attached to pull down the parachute to ground level. Once this was done we were able to free the sonde from the other tree and lower it safely to the ground.

Recovery of the parachute.

Finally, the sonde is recovered!

The sonde is recovered.

The recovery was not only hampered by the height of the tree, but also, this being a walnut orchard requiring extensive multi-day watering, massive amounts of mud were encountered, making for very slippery conditions. And apparently recycled waste water is used for irrigation – so not exactly pleasant conditions if you can imagine.

Some technical information about the sonde is available by clicking on the image below:

Sippican Microsonde IIA Teardown

Category(s): Sonde
Tags: ,

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.