If you are a student (undergraduate or PhD) from an ESA member state or Cooperating State and you are studying in an ESA member state or cooperating state and you are aged 18-28, then ESA may have a project for you.
The Rocket-borne Experiment for University Students (REXUS) and Balloon-borne Experiments for University Students (BEXUS) are run by Germany and Sweden. The Swedish share of the payload has been donated to ESA to be made available to students in other states. ESA wants to hear from students who can design an experiment to be flown by balloon or rocket.
Deadline to apply for this is the 18th of November. Entries will be judged and the winners announced on the 18th of December. Further details on the program and application instructions are here.