Figure 6: Drakon representation of launch detection code

4. SOFTWARE

The autonomy of the autopilot software had to be increased,
especially for possible phases of lost datalink with no
possibility of manual intervention.

These situations rarely occur in close range testing.
Some of the logic implemented is dictated
by the safety regulations of the flight test range. Another
challenging phase is the release of the plane hanging from
the balloon, where automation is most important since it is
the point of maximum distance to the ground station and the
process needs quick automatic sequencing.

Mission execution

For programming automatic mission state switching and
safety logic our software had to be extended. Like the
hardware of our system, the software is modular, so we could
add components rather then having to alter existing code.

To code these critical functions we are using the DRAKON
Editor software originally developed for the Russian space
program [8].

It allows to graphically program flow diagrams
which are checked for consistency. C-code is generated from
the diagrams. The start detection logic is shown in Fig. 6 as
an example.