Telemetry

Telemetry is at the heart of our communication system and handles bidirectional data exchange before, during, and after the flight. The ground station, featuring a custom-developed user interface, serves as the interface between our ground team and the rocket. It enables the transmission of radio commands—such as those used to arm the rocket—as well as the reception of data packets from the rocket. Our data packets contain encoded information about the rocket’s status, its position, and other sensor data. With this data, we can track the flight’s progress from the ground, detect problems early on, locate the rocket after landing, and analyze the flight later on in case our onboard storage media fail.

All our data is transmitted via high-performance radio transceivers in the 169 and 869 MHz SRD bands. The system is designed for a data rate of 1.2 kbps with a range of nearly 20 km to ensure it is suitable for our ambitious projects. We handle the development and manufacture of the antennas ourselves: On board the rocket is a QFH antenna with omnidirectional radiation characteristics, while the ground station features a helical antenna with high directivity. The antenna design is verified using FDTD simulations conducted in-house.

We share all development progress under an open-source license on GitHub: github.com/Spaceflight-Rocketry-Giessen-e-V/Telemetry

Recovery / Staging

EAGLE (“Electronic Actuation & Guidance for Landing and Elevation”) monitors the entire flight, from takeoff to landing. It is responsible for stage separation and the deployment of the parachutes at apogee. It also includes an active system for controlling altitude using air brakes. The flight is continuously monitored, the achievable altitude and current speed are calculated using a Kalman filter, and the altitude is regulated by adjusting the drag. This enables precise control to reach the specified altitude as accurately as possible.

We are developing a unified software library for EAGLE to make it as easy and reliable to use as possible. This will also make it easier to integrate future updates.

Sensorics

Our sensors collect a wide range of environmental data, including temperature, pressure, and the rocket’s orientation and position. They also measure mechanical stresses and vibrations. The collected data is stored on our sensor boards and transmitted to the telemetry system, which relays the most important data to the ground station. Thanks to this precise data collection, we can analyze the flight path in real time and later on with great accuracy, identifying potential improvements and problems.

Power Supply

The power supply provides the other subsystems with various voltage levels. We place great emphasis on stability during normal operation as well as the ability to deliver higher currents under load conditions. In addition, high current spikes must be tolerated for the ignition of the propulsion system, the staging process, and the deployment of the parachutes. Due to the high requirements of our telemetry system regarding electromagnetic interference, we use linear voltage regulators despite their lower efficiency. To prevent damage to the components, the heat generated must be efficiently dissipated. In the future, the power supply is intended to switch seamlessly between a wired supply and the rocket’s own LiFePO4 battery to allow for long wait times on the launchpad. The battery voltage is continuously monitored and transmitted to the ground station via the telemetry system.

ASCENT I

Our first flight computer, ASCENT I (Advanced System for Control Electronics, Navigation, and Telemetry), was developed for the PIPE rocket. It laid the foundation for our work and tested many different concepts:
– Modular design with a central data bus
– Sensor system with a GNSS receiver for position determination
– Redundant deployment of the parachute system
– Telemetry system for transmitting collected data
– Data storage using various storage media

Through the launch of PIPE and the practical testing of ASCENT I, we were able to gather a wealth of insights that we are incorporating into our ongoing development efforts. These include, among other things, the importance of communication between subsystems, the benefits of thorough testing prior to launch, and the need for debugging capabilities such as signal line tap points and debugging LEDs.

ASCENT III

We have been developing the ASCENT III flight computer for our ARCHER competition rocket since 2026.
Compared to our previous flight computers, we ensure compliance with EuRoC’s strict competition rules, for example regarding power supply, the telemetry system, and the activation of the landing system and staging.
We strive to apply the KISS principle (keep it simple and stupid) as best we can. We rely on the proven technology of ASCENT I and II, but, for example, we combine several independent sensor systems and data storage units.
We have further refined the circuit board layout, resulting in more space for our systems and a more efficient use of the bus. In addition, each system features native USB-C ports for programming and data transfer