Russian-born Danja Vasiliev and New Zealander Julian Oliver are part of a growing movement of coders and hackers who use their skills to create questioning and humorous digital art. Along with Gordan Savicic, they wrote the Critical Engineers manifesto, which posits: "The greater the dependence on a technology the greater the need to study and expose its inner workings, regardless of ownership or legal provision." Through their art, Oliver and Vasiliev are focusing on showing how vulnerable the public is to mass surveillance. They create visual, interactive digital objects, do street interventions and performance, and use engineering to comment upon the world we live in. "Engineering is perhaps the most transformative language of our time. Engineering shapes the way that we move, communicate and think," Oliver says. Oliver and Vasiliev's past projects include "Men in Grey" (2009 - 2014), in which the artists dressed in grey suits and carried briefcases displaying private messages that people sent in public, networked places, such as cafes with wifi. As Oliver explains, he creates projects "which engender a healthy paranoia". We follow the duo and their colleague Bengt Sjölén as they construct and launch their latest project: a weather balloon modified with a computer and radio scanning equipment to monitor and intercept what is impossible to pick up from Earth - transmissions in the upper atmosphere. They are particularly interested in the unmanned aerial vehicle drone-to-satellite microwave signal domain and expect to reveal secret drones flying above Europe that rove above our heads. We see them build the technical side of the balloon, negotiate the flying licences and launch site, and fulfil the legal requirements before they send the balloon on its 30km vertical journey to the edge of space, which we see from the balloon-cam. The team then interpret the data and turn it into visual representations of the objects and communications taki