Tracking aircraft and spacecraft has long since been a daunting challenge for engineers. Long before the advent of GPS technology, tracking airplanes from the ground (from the point of view of an air traffic controller, for example) always involved some sort of bulky primary or secondary radar technology, weighing many tens of pounds and consuming a significant amount of electrical power (both on the ground and in the air). Airplanes even had trouble tracking themselves, let alone making it easy for others on the ground to know where they were flying. In fact, standard procedure for most airliners traveling over the pacific before the rise of GPS was to use what is known as an inertial navigation system, literally an array of gyroscopes, motion sensors, and accelerometers, to determine their approximate position over the ocean. These systems would drift by an approximate amount of 400 meters per hour, sometimes leaving an airlines many miles off course once it reached land. These days GPS has replaced these navigation systems and airlines no longer need to use maps, VORs, and other non-GPS systems as primary position sensing equipment.

This is very fortunate for the high altitude balloon community. There is basically nothing on this planet that can beat the simplistic, low-cost nature of a GPS receiver. While there are other ways to acquire one’s position and altitude above the Earth’s surface, GPS receivers have certainly dominated the market — and for good reason. They are low-cost (~$20), consume little power (~100mW), small (~0.3 cubic inches), and lightweight (~5g). That being said, a GPS receiver is … well, only a receiver. That means all it can do is receive information from GPS satellites and determine its own position. It has no way of physically transmitting its own information from, say, a high altitude balloon, to a user on the ground intending to track said balloon. So, if the user wants any chance of recovering his or her altitude balloon once it lands, he or she needs to be able to determine its location. That’s where things get more complicated, and more interesting!

For the average balloonatic (no, we didn’t invent this name, but it does accurately describe us!), there are essentially two ways to remotely receive information from a high altitude balloon. Each method has multiple ways of being implemented, and each implementation has its advantages and disadvantages. In very loose and basic terms, these two methods are via satellite, or amateur radio communications. Let’s analyze both of these methods and a few of their implementations a little more closely.

1) Satellite Communications

There are an array of satellites flying above all of the world, providing communication channels for almost any sort of application. These satellites can be used for uploading information from a high altitude balloon to the internet, or to any properly configured satellite receiver on the ground. Satellite communication is generally very reliable, expensive, heavy, and slow. The required hardware for a satellite transceiver (i.e. transmitter + receiver) is complicated and sometimes power hungry. But hey, it’s super reliable, robust, and, provided you use the right supplier (hint hint: Iridium), your balloon will be able to communicate with you from anywhere in the world. That is one a good sell, provided you have the money, space, weight, and power capabilities to handle such a beast. So how does it work? Basically, a satellite transceiver has a transmitter and a receiver inside itself that it uses to communicate with an array of satellites flying above it. It requires an antenna pointed towards the sky to talk to the satellites. It can send and receive information from the satellites. The two most common ways of using satellite communications for tracking high altitude balloons are through the two following products:

(a) SPOT Tracker:

The SPOT Tracker is unique, robust, efficient, extremely reliable, and very simple to use. It is the easiest way to track your high altitude balloon with an extremely minimal amount of effort. The SPOT Tracker comprises of a GPS receiver and a Satellite transmitter (note, no satellite receiver) using the Globalstar network. It comes off the shelf, ready to go, and takes four AAA batteries (make sure to use low temperature rated batteries if you plan on flying it on a high altitude balloon!). Essentially what it does is every 10 minutes it turns itself on, acquires a GPS lock to receive its position, and then sends this position along with the current time to the Globalstar network. This information is then uploaded to the internet on the SPOT website, where the user can track his or her high altitude balloon. The SPOT then turns itself off for 10 minutes to conserve power. It typically lasts for 2 weeks on a single set of AAA batteries. Below we have outlined the pros and cons of the SPOT.

Advantages:

1. Comes ready to use out of the box
2. Robust and efficient
3. 2 weeks of battery life
4. Water proof
5. Built-in GPS receiver
6. Transmits GPS coordinates every 10 minutes online.
7. Great backup method.

Disadvantages:

1. Expensive ($99 for the module, and $149 a year for subscription)
2. Large (~5 cubic inches)
3. Heavy (150g)
4. Only a one-way communications channel. There is no way to communicate with the SPOT.
5. Only transmits GPS coordinates every 10 minutes. There is no way to determine altitude.
6. If your payload lands upside down in between transmissions, chances are you will not be able to recover.
7. The SPOT disables transmissions above a certain altitude (in our experience this has been around 60,000 feet), meaning you will only have data while your balloon is below said altitude
8. Irregularities — sometimes the SPOT just stops working for an hour due to poor signal reception (don’t ask).

Having over 60 high altitude launches under our belt, we do not recommend to use the SPOT as a primary navigation and tracking system. The SPOT is perfect as a backup tracker in case your main avionics fail, but its disadvantages really lead us to pursue a different method of primary communications.

(b) Iridium 9602/9603 Modems

Iridium 9602/9603 modems are expensive, but lightweight, reliable, and downright awesome! They can essentially be treated as texting from a cell phone with two minutes of delay per text. Iridium has 100% world coverage, and fairly reasonable usage costs (somewhere around 8 cents per 50 bytes of data, which can be compressed to improve efficiency). However, these modems require a host computer, and are not standalone devices. This allows for more customization over the data sent, but also increases complexity. Furthermore, these modems do not have a built in GPS, so the user will need to supply a high altitude capable GPS, acquire this information from the GPS, and send it over to the Iridium modem. Our Loonar Technologies Expansion board incorporates a fully integrated Iridium system, with no effort required on behalf of the user.

Key Features:

1. Ability to send and receive up to 300 bytes of any type of data every 2 minutes.
2. Cheap — $150 sunken cost for modem, $0.08 per 50 bytes of data sent.
3. Two way communication — essentially like texting on a cell phone, but from anywhere in the world!
4. Compatible with almost all micro-controllers.
5. Power consumption of approximately 250mW on average.
6. Does not require a HAM license to operate.
7. Has a unique “triangulation” feature that can track itself without a GPS! (Albeit only to a certain accuracy that can be a few kilometers).
8. Requires GPS receiver for position sensing.

2. Amateur Radio Communications

While satellite communications are reliable and interesting, they certainly have some drawbacks that you may have noticed. First, they are notoriously expensive, have operating costs even after you buy them, and are quite slow. Being able to talk to your payload every 2 minutes may not be something you can afford. Imagine if SpaceX could only know what was going on with their rockets every 2 minutes! Not only that, but they would only be able to send 300 bytes every 2 minutes! That’s not exactly the golden standard for aircraft/spacecraft communications. That’s where other types of radio communications come into play. For the average Balloonatic, amateur radio communications is a real winner. While it does have some disadvantages (like the requirement for a HAM radio license — not hard to get, by the way — and the fact that it will only work in some parts of the globe), the does carry with itself certain advantages that really cannot be ignored. Let’s take a look at some implementations:

(a) APRS Transmitters

The Automatic Packet Reporting System (APRS) is an amateur radio-based system for real time digital communications of information of immediate value in the local area. Data can include object Global Positioning System (GPS) coordinates, weather station telemetry, text messages, announcements, queries, and other telemetry. APRS data can be displayed on a map, which can show stations, objects, tracks of moving objects, weather stations, search and rescue data, and direction finding data. High altitude balloon enthusiasts often use APRS transmitters for tracking their payloads because they are cheap and easy to use.

Advantages:

1. No operating costs
2. Ability to send more messages per unit time in comparison to above satellite technologies.
3. Since APRS is a widely used technology, the user can rely on an array of already implemented receivers across the world.

Disadvantages:

1. Requires a HAM radio license to operate.
2. Requires external GPS for position sensing.
3. Does not have full global coverage.
4. Does not work well below a certain altitude, depending on terrain and distance to the nearest receiving station.
5. One-way communication only — no way to send information to the balloon.

While many balloon users use the APRS system for tracking and navigation, our experience has been that the disadvantages of such a system are not worth the hassle. For starters, one-way communication is generally a no-go for us. If you wanted to remotely cut down your balloon from the ground, for example, APRS would be useless. Second, you are really relying on other people to receive your APRS signal for you. While this may seem like an advantage (and in some ways it is), relying on others to do work for you is not always the best course of action. Therefore, for these reasons, Loonar Technologies does not offer APRS transmission capabilities. Instead, we have designed our own customized radio system to overcome these disadvantages.

(b) Other Custom Radio Transceivers

* Ground side transceiver above, balloon side transceiver below.

Given the many disadvantages of APRS, we set out to build our own radio system capable of offsetting these undesirable traits. Our Loonar Radio Transceiver system allows for two-way radio communication in the VHF 144–148 MHz amateur radio band frequencies, with the ability to send any and all customized data to and from a high altitude balloon.

Advantages

1. Can support extremely high bandwidths, up to many kilobytes of data per second.
2. Full two-way communication.
3. Extremely low power, <100mW.
4. Lightweight (~3g).
5. Standalone device — plug and play.
6. Interfaces with the Loonar Technologies website and allows for seamless tracking and data transfer.
7. Low-cost ($99)!
8. Works down to -55 Celsius!
9. Includes integrated high altitude GPS.

Disadvantages

1. Requires a HAM radio license.
2. Requires the user to have his/her own radio receiver within line of sight range of the payload (we provide this).