Meet the Graz 2025 APEX Team
The REXUS/BEXUS program, realized under a bilateral Agency Agreement between the German Aerospace Center (DLR) and the Swedish National Space Agency (SNSA) and supervised by the European Space Agency (ESA), provides the opportunity for students from European universities to fly experiment concept on two sub-orbital sounding rocket (REXUS) and two stratospheric balloons (BEXUS) every year.
The goal of the Graz 2025 APEX team is to investigate the polarization of the light emitted by the aurora borealis, the northern lights. Auroras are caused by high-energy particles from the Sun interacting with the Earth's upper atmosphere. The aurora is a natural laboratory for plasma physics, and understanding its dynamics provides an insight into the interactions occurring at this boundary layer where space weather interacts with the neutral atmosphere and local magnetic/electric field. In this respect, the polarization of the light emitted by the aurora is a tracer to local interactions, such as variation in the density and fields. While previous ground-based measurements have detected linear polarization in the green (557.7 nm) and red (630.0 nm) lines, respectively around 1.5% and 5%, it is impossible to absolutely rule out contamination from atmospheric scattering along the line-of-sight. As a crucial step to confirm these ground-based observations, APEX will provide the first-ever measurement of the auroral polarization from above the atmosphere.
To measure the aurora, APEX uses two cameras with narrow-band filters allowing only light from the red and green emission lines to be recorded. The cameras themselves have polarization filters directly mounted on the sensor chip to determine the light´s linear polarization. The cameras are installed on a three-axis stabilized gimbal, which will keep the cameras pointing and stable towards the aurora for several seconds during each exposure. In order to point the cameras, the system determines the aurora’s position relative to the rocket by using a prediction algorithm in combination with sun sensors and magnetometers (three-axis compasses).
APEX is the first REXUS/BEXUS project of the Aerospace Team Graz (ASTG) student association. The association consists of over 90 members from diverse fields of studies like Physics, Electrical Engineering, Mechanical Engineering, Information and Computer Engineering, Computer Science to name only a few, from both the University Graz and University of Technology Graz. Their level of study ranges from Bachelor to PhD candidate. The core APEX team is composed of about 15 members of the ASTG, and additional members of the association have contributed to reviews and supported APEX with advices and organization. Dr. Gabriel Giono from the Space Research Institute (IWF) is the main supervisor of APEX and proposed the initial concept for the experiment. The IWF is supporting APEX with supervision, reviews by experienced engineers, infrastructures for testing, and procurements of some of the components.
The APEX team is organized in five main branches: Project Management and System Engineering, Science, Mechanics, Electronics, and Software. The team meets weekly for a general update on all systems and has smaller meetings in between to discuss subsystems or work in the ASTG workshop. A first version of the experiment is being assembled and tested during summer 2025, while the flight campaign is scheduled for March 2026.
Events of ASTG@IWF
March 27, 2026
APEX post-launch event
After two and a half years of hard work, APEX finally set to launch in mid-March 2026 from Esrange in northern Sweden. Following the flight to an altitude of over 70 km, the students will present the result.
September 4/5, 2025
ASTG @ Graz in Space
ASTG presented last year’s rocket ALCEDO as well as the Auroral Polarization Explorer (APEX), which is being developed in collaboration with the IWF, during the event "Graz in Space 2025".
April 3, 2025
SPECTRE: SPacE proof of Composite Tape-springs boom on REXUS Experiment
Two Members of the SPECTRE team (REXUS rocket experiment) from KTH Stockholm (Sweden) gave an overview talk on their project on April 3, 2025, at the IWF.
The objective of SPECTRE is to validate a self-deploying rigid boom mechanism in space. Developed by KTH, this bistable composite tape spring system will endure rocket launch forces, deploy in microgravity using the energy stored in the bi-stable composite tape springs, and function under vacuum conditions. Drawing inspiration from the lessons learned in the prior B2D2 (Bistable Boom Dynamic Deployment) experiment, SPECTRE comprises two main units: a Free-Falling Unit and a Rocket Mounted Unit. The FFU will be ejected from the REXUS rocket, comprising the boom deployment mechanism, a Recovery Unit, 3 cameras, and 2 Inertial Measurement Units to record the boom deployment dynamics, capturing essential data such as initial oscillation amplitudes and damping times. The collected information will be stored in the Recovery Unit, which will emit a GPS signal for precise location tracking. Upon recovery, the data from these sensors will undergo a detailed analysis to quantify the performances of the boom and enable benchmarking. SPECTRE places utmost priority on the successful deployment of the boom and represents a critical step towards enhancing boom deployment mechanisms for its prospective application in nanosatellite missions and space exploration.
Februar, 2024
ASTG Concept Review Meeting
Following up on the concept workshop held in early February the APEX Team held a concept review at the IWF. All concepts were weight for their advantages and disadvantages. The result: The camera gimbal as proposed already last year is still the best compromise between technological difficulties and science gained.