Technology of remote sensing in the terahertz range (frequency interval arbitrarily set between 0.1 - 30 THz) is the object of considerable development efforts addressed to a number of new civilian and military applications. Technical challenges appear in the THz sensing of temperature differences above an existing hot surface target, such as radiation patterns produced by high energy electrons in laboratory accelerators, and thermal differentiated structures in the solar disk in space. The efficient suppression of radiation in the visible and near infrared (set arbitrarily for wavelengths < 10 ¿¿m) is an essential requirement. An experimental setup has been prepared for testing at room temperature THz materials and detectors, aiming the detection of solar radiation. A custom-made detector consisted in a room-temperature micro-bolometer INO camera with HRFZ-Si window. The THz transmission of two ¿¿low-pass¿¿ membranes were tested for black body temperatures ranging 300-1000 K: Zitex G110G and TydexBlack. It has been demonstrated that both are effective suppressors of radiation at wavelengths < 15 ¿¿m, with the first one exhibiting a small radiation excess, that may be attributed to small visible and NIR allowance. We describe optical setups prepared to detect solar radiation, consisting in a microbolometer camera preceded by a photon pipe, low-pass membrane and band-pass resonant metal mesh, placed at the focus of the 1.5 m reflector for submillimeter waves (SST) at El Leoncito, Argentina Andes.