We detect terahertz radiation emitted by a blackbody object at room temperature. The probe consists of semiconductor detectors coupled to
the cold finger of a compact cryo-cooler. The detectors are narrow conductive channels in two-dimensional electron gas, which is sensitive to
variations of photon flux through the mechanism of excitation and rectification of plasma waves. The excitation has a resonant nature, with
an unexpectedly narrow FWHM, below 10%. The key element of the concept is a compact cryo-platform, which enables us to use highly sensitive
cryo-detectors, while keeping the system compact,  34 cm side, and mobile. We discriminate the temperature variation of the blackbody
object as small as 1.0K at a distance of 1 m. There is room for further optimization of the detectors and optical systems to boost the
temperature resolution down to 0.5K and the operation distance to 5 m, which are needed for practical applications.