A time for reflection...

We have constructed a radar reflector for the Chase in Space rig. This device will help our spaceship show up on aircraft radar. There has never been a reported collision between a weather balloon and an aircraft and we wish to keep it that way!

What are radar reflectors?
Radar reflectors are simple devices that are used to make something more visible to radars. For example, kayakers in foggy areas use radar reflectors to avoid being run over by bigger boats (with the radars); weather balloons have reflectors that allow them to appear in Air Traffic Control radars, and so on.

How do they work?
They are typically built to have reflective surfaces (eg of metal) in 3D at 90-degrees at each other. Incoming radar waves bounce off one, two, three surfaces and head back to the source direction. The principle behind them is similar to the one that makes you always see your 'eye' in the point where two mirrors cross each other at 90 degrees. 
(source: http://www.instructables.com/id/Lightweight-Radar-Reflector/)