1. Demonstrate altitude hold and piloted altitude excursions
2. Demonstrate the tetroon envelope design
3. Investigate envelope heating
4. Record temperature, pressure, humidity data
5. Demonstrate 434MHz radio communication over long (>300Km) range
6. Use solar power
7. Demonstrate cruising in polar stratospheric vortex
8. Experiment with altitude hold algorithms based on envelope temperature, payload mass, atmospheric density and other factors
9. Reuse existing code and pcb designs as much as possible

This design should be capable of cruising at 16 to 18Km for 5 days, enough for a circumnavigation in the polar stratospheric vortex.

Wikipedia tetrahedron page

some info on tetroons