Tracking & Recovering Your Weather Balloon Payload
Most amateur high altitude balloon flights aim to recover their entire payloads. Usually, this is to obtain onboard data, photos, videos or just to reuse the package again on another flight. In order to do this, you’ll need to have some sort of onboard tracking system so you can follow your flight and find the landing location when your mission is completed. Most of the time, you’ll lose visual contact with your weather balloon payload after just a few minutes so you’ll need to rely on something that can record and relay the weather balloon’s position throughout the flight. There are three typical methods that are used for this: amateur radio system, GPS messaging systems, cellular data systems. For reliability, you should implement at least two of these methods so you have a primary tracking system and a backup in case something goes wrong. Below are the details for each method.
Amateur Radio Tracking
Using amateur radio (ham radio) signals to track your high altitude balloon flight is by far the best option and we strongly recommend utilizing this method. Not only is it the most reliable method, but it is also very rewarding to develop and/or configure a computer tracking system yourself! Using a radio tracking method will allow you to receive positioning reports throughout the entire flight in roughly one minute increments. This allows you to follow the entire flight all the way up to burst altitude and even predict the landing location in realtime while the weather balloon payload is still in the air! In the United States (and many other countries), you’ll need to obtain an amateur radio license first, which is not that hard to get. You’ll need to do some minimal studying and take an amateur radio test to obtain a license. Check out the ARRL’s guide to get started. The best tracking method to start with is using the Automatic Packet Reporting System (APRS) which only requires a Technician license in the US. This is the first stage of FCC licensing and the easiest to obtain. Once you’re licensed, you can either purchase a pre-built radio tracking system or build your own radio tracking system with a small computer like an Arduino or a Raspberry Pi.
If you want to use one of our prototype tracking systems, you can purchase our bare circuit boards here. Our experimental prototype circuit boards include just the bare circuit board, a parts list and assembly instructions. You would need to purchase the electronic components and complete the solder assembly separately, but we’ll provide you a list of parts and where you can purchase them — mostly from Amazon. We don’t guarantee perfection, but these are the exact systems we use for our flights. We’ll have a full kit with all the parts included available for purchase soon!
To access our Arduino source code we use on our flights, see our GitHub repositories here.
GPS Messaging Systems
Using a GPS Messaging System to track your high altitude balloon flight is the second best method available. These systems are fast and easy to get up and running and don’t require a license to use, however, they are usually much more expensive and require an annual subscription to use the GPS Messaging service. The most popular GPS Messaging System used for weather balloon flights is the Spot 3 Satellite Messenger. This system will work anywhere in the world and just needs a clear view of the sky, but there are some downsides and things to consider. First, the system will only operate to approximately 60,000 ft (18,300 m) in altitude. These systems aren’t designed to be airborne so the system will lose it’s GPS fix above the maximum altitude, however, it should regain a GPS fix during descent. This limitation means that you won’t be able to obtain a definitive maximum altitude reading unless you have some other onboard system recording altitude. Secondly, the GPS System requires a clear view of the sky and should be pointed upwards for the best signal. Payloads have been lost simply by landing upside down or on it’s side causing the GPS System to lose signal. To help mitigate this risk, you can use something like an onboard weighted hamster ball or another similar method to create a gimbal system that will force the GPS device to always point upwards no matter how your payload lands.
Cellular Data Systems
These systems are the worst and we strongly recommend avoiding them in most circumstances. If you must use one, it should be only as a backup method and you’ll need to take special care to comply with FCC airborne cellular device rules. To start with, your landing location will require a good cellular data signal in order to have any chance of reporting it’s position. This is hard to predict and rely on. Secondly, per FCC rules, you cannot use a cellular device while it is in-flight. This means that you cannot obtain realtime positioning during the flight and can only use the device to report it’s final landing location. Even without considering the FCC rules, cellular towers are pointed towards the ground so you couldn’t even obtain a signal once you get a few thousand feet above the ground. Additionally, to comply with FCC rules, you would need to implement a custom application that turns on Airplane Mode (disables the radio) once you launch your weather balloon and then automatically disables Airplane Mode (enables the radio) upon landing. The radio must be off while the high altitude balloon is airborne. This can be done, but it is a lot of work. The only benefit is that if you do all the work to comply with FCC rules, it can be an inexpensive backup method. You could potentially use a cheap pre-paid Android device and write a custom Android application to enable/disable Airplane Mode.
If using a GPS Tracking System like the Spot 3 Messenger, be sure to mount it with a gimbal system, like this one by @TheSpaceGal, to ensure the GPS always points upwards no matter how it lands.
— Emily Calandrelli (@TheSpaceGal) May 10, 2019