The purpose of the Solar-tracking Radiometry platform is to maintain optimal viewing angles of radiance sensors recording water-leaving reflectance (water colour), avoiding sun glint and platform shading even from moving platforms such as ships or buoys. The system is developed to operate autonomously, with low power consumption, integrating commercially available (ir)radiance sensors and providing remote connectivity. All hardware and software are open-source, through this repository and the associated software repository (https://github.com/monocle-h2020/so-rad). Their use is licensed under a creative commons non-commercial license. To discuss commercial use please contact the authors at stsi@pml.ac.uk. This repository contains the following: Construction manual focussed on electronics and software configuration, including these appendices: A photographic step-by-step instruction of the controller box layout A series of CAD drawings as drilling templates and component positioning and wiring CAD drawings describing a PVC motor-enclosure Installation Guide detailing how to deploy the So-Rad in the field