{"id":26247,"date":"2026-08-21T07:24:36","date_gmt":"2026-08-21T05:24:36","guid":{"rendered":"https:\/\/oewf.org\/?p=26247"},"modified":"2026-08-21T07:24:38","modified_gmt":"2026-08-21T05:24:38","slug":"the-instrument-that-follows-no-script-inside-caillous-software","status":"publish","type":"post","link":"https:\/\/oewf.org\/en\/2026\/08\/the-instrument-that-follows-no-script-inside-caillous-software\/","title":{"rendered":"The Instrument That Follows No Script: Inside Caillou’s Software"},"content":{"rendered":"\n

In this article our intern Nikola Ivanov writes about the software that turns a Raspberry Pi, a laser and a camera into an instrument an operator can run from the habitat, or, in the fiction of the mission, from another planet.<\/strong><\/p>\n\n\n\n

The hardware side of Caillou was settled fairly early: a Raspberry Pi 4, a camera module, a visible guide laser, three status LEDs and a fan, all inside a 3D-printed enclosure. The software side was much less clear to me. What should the instrument decide by itself, and what has to stay in human hands?<\/p>\n\n\n

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\"Nikola<\/a>
Nikola Ivanov writing software for an analog mission (c) OeWF<\/em><\/figcaption><\/figure>\n<\/div>\n\n\n

One command at a time<\/strong><\/p>\n\n\n\n

My first sketches described the mission as a script. Power up, wait until the rover arrives, aim the laser, take a picture, simulate the acquisition, transmit the results. Written down like that it looked like a tidy state machine, and on paper it worked fine.<\/p>\n\n\n\n

In practice it would have been a trap. Field work is not linear. An operator repeats a measurement because the first one looked odd, aborts halfway through, takes a second image of the same rock, or moves on to a new sample while the previous data is still sitting on the device. Software that insists on one fixed order ends up fighting the people using it.<\/p>\n\n\n\n

So I turned the design around. The instrument holds no mission sequence at all. It offers a handful of independent commands instead, each one handled by its own background worker, and each one valid at any moment:<\/p>\n\n\n\n