It is the COM design team wearing our high altitude balloon tracking hat and we will introduce the Balloon Tracker subsystem we used last week to safely recover our ballon:
Obviously this is a module which will not fly on the satellite but has important role in the test campaign. During the development of MOVE-III we will have multiple high altitude balloon flights to test the system and prepare the team for a launch campaign. During a balloon flight the system ascends up to 40km altitude with the help of a helium filled weather balloon. After the balloon bursts the rest of the payload-train will descend slowly using a parachute. During this time our team has no real control over the trajectory of the balloon, the path is the matter of the winds. We can make simulations beforehand which has an amount of uncertanty as they use predicted weather data.
To find the valuable equipment the balloon has to be tracked. While the satellite itself is planned to have a special GPS module on board which can operate even Low-Earth-Orbit, that is the device under testing. This means it should not be trusted during the test with a crucial task like tracking. To solve the problem there will be an additional gondola next to the satellite which is responsible for live tracking and landing site determination. The Balloon Tracker Gondola contains two different GPS trackers, both operate on their own and completely independent from the satellite. For live tracking information an APRS module is installed. APRS stand for Automated Packet Reporting System and is used for various tasks from automated weather station reporting to vehicle identification and tracking. It is also popular among high altitude balloon teams since it does not require to build your own dedicated ground station. The APRS transmitter on board of a balloon sends a standard radio message with geocoordinates periodically. This message is received by multiple stations on the ground maintained by the amateur radio community. These stations connected to the internet and forwards all incoming packets to the APRS database, which is available for everyone. Several ready made tracking maps can be found on the internet or an API can be used for custom tracking software. The APRS in our Balloon Tracker has a special GPS receiver. While most commercial GPS modules restricted in altitude and speed, to prevent their use in military applications, our receiver operates up to 50km of altitude (but still has speed limitation). This way we can have live tracking data for the whole flight.
The APRS module is accompanied by a GSM-GPS tracker, which has a standard GPS receiver and can be connected through the cellular network. By sending an SMS to the tracker it would respond with a message that contains the geocoordinates. This module can only operate up to a certain altitude since the cellular network is designed to work on the ground and connection will be lost during ascending. This GSM-GPS tracker is ideal to identify the landing area in high precision.
The current Balloon Tracker is built completely from commercial modules, all selected from trusted manufacturers with high altitude ballooning experience. And as we can say a week later, things worked out pretty well, we got our balloon again!