Astronomical observations at infrared, sub-millimetre, and millimetre wavelengths are essential for addressing many of the key questions in astrophysics. Future ground- and space based observatories need large detector arrays with a sensitivity limited only by the noise of the radiation background. We demonstrate that antenna coupled Microwave Kinetic Inductance Detectors allow us to create kpixel large arrays with background limited sensitivity over the entire FIR/mmwavelength range. We discuss in detail the readout system and experimental results of a 961 pixel array, optimised for 850 GHz radiation that is read out with a single readout chain.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Tera-Hertz SensingQN/Quantum NanoscienceQN/Mol. Electronics & Device