The measurement of absolute magnitude is made with an instrument called a bolometer. Thallium selenide has been used in a bolometer for infrared detection. He published an 1881 paper on it, "The Bolometer and Radiant Energy". A number of superconducting and non-superconducting cooled bolometer technologies exist. A bolometer power sensor converts incident radio frequency power to heat. Bolometer arrays are arrays of bolometer receivers which measure the energy of incoming radio photons. It is also planned to install a bolometer camera at millimeter wavelengths. In 1880 Langley invented the bolometer, an instrument initially used for measuring far infrared radiation. An attempt to reactivate the bolometer sites was made in mid-1943 but abandoned by July. In structure and function it resembles a biological version of warmth-sensing instrument called a bolometer. The term bolometer is also used in particle physics to designate an unconventional particle detector. A bolometer can be used to measure power at microwave frequencies. In contrast, in a bolometer, light heats up a tiny piece of material. Langley invented the bolometer and discovered infrared radiation from the sun. During July and August, two new bolometer sites commenced operations near Algeciras and Ceuta.