If you've ben following my ramblings for a while now, a while back I had set up a small radio monitoring station that tracked any weather balloons (or to be more accurate, a weather sonde) that floated by. utilizing a Raspberry Pi and a SDR dongle.
One of the neat things with the set up is that it also gives me the ability to monitor what the receiver is seeing via a local web page interface which gives me a live map plotting of any sondes that are being picked up.
Recently my receiver picked up a sonde that looked like it was about to land nearby. My station lost the signal when the sonde was at about 300 feet altitude. Looking at the map on my web page, I saw that the sonde seemed to have landed fairly close to a gravel road (as opposed to say a swamp or a woodlot) - meaning that the likelihood that I could actually recover the sonde was quite good.
Armed with a possible location I hopped in the car and headed on over to where the sonde was last seen. After travelling down a pretty muddy back road, I found a very bright orange parachute draped over a fence by the side of the road with a long length of string that had a white Styrofoam box tied to the end of it.
I quickly gathered everything up and quickly ran home to give things a closer look.
Of course there was the orange parachute and the remnants of the balloon, but it was the actual sonde itself that I was most interested in.
On the surface it was a simple foam box with a wire antenna on one end and a metal sensor sticking out of the side. There was a couple of glowing LED's that indicated that it was still "live".
Underneath the sonde was a USB connector - which I am assuming is needed to configure the sonde, and a push button which I assumed was how the electronics were turned on or off - this was ultimately confirmed when I pressed the button and the LED's turned off.
The key information that I got out of this were the markings on the side of the sonde - particularly the markings that announced that this device was a GRAW DFM-17 with a handy web address. This gave me all that I needed to find out what this thing did.
I will eventually unwrap the Styrofoam wrapper to see what was actually inside, but for now, let do a bit of an overview on what this thing is.
The GRAW DFM-17
What It Does
As the balloon goes higher and higher, the DFM-17 measures:
- Air temperature
- Moisture in the air (humidity)
- How fast and in what direction the wind is blowing
- How high it is above the ground
This information helps meteorologists understand what is happening in the atmosphere at different heights, not just at ground level.
How It Works
The DFM-17 uses a GPS receiver to figure out its position as it moves. By tracking how it drifts with the wind, ground stations can calculate wind speed and direction at different heights. At the same time, built-in sensors measure temperature and humidity.
All of this data is transmitted back as live data to a receiving station while the balloon is in flight.
Why It’s Important
Weather balloons with radiosondes like the DFM-17 are a key part of weather forecasting. The data they collect is used to:
- Improve daily weather forecasts
- Track storms and severe weather
- Help aviation plan safe flight routes
- Support climate and atmospheric research
Without these measurements, forecasts would be far less accurate.
What Happens After the Flight
The balloon eventually bursts at very high altitude, and the DFM-17 falls back to Earth via the parachute that the sonde deploys automatically when the balloon burst is detected. Since most sondes are usually not recovered, they are usually designed to have minimal impacts to the environment.
In Simpler Terms
We can think of the GRAW DFM-17 as a flying weather station. It rides a balloon into the sky, measures the conditions along the way, and sends that information back so weather experts can better predict what’s coming.
So the next thing on tap will be to open the thing up and take a look at the innards, which is the plan for the next time I post.
