History of the telescope of the IRAS satellite in 1983 revolutionized infrared astronomy from space. This reflecting telescope which had a mirror, operated for nine months until its supply of coolant (liquid helium) ran out. It surveyed the entire sky detecting 245,000 infrared sources—more than 100 times the number previously known. Although optical telescopes can image the near ultraviolet, the ozone layer in the stratosphere absorbs ultraviolet radiation shorter than 300 nm so most ultra-violet astronomy is conducted with satellites. Ultraviolet telescopes resemble optical telescopes, but conventional aluminium-coated mirrors cannot be used and alternative coatings such as magnesium fluoride or lithium fluoride are used
Simple Model of the Atmospheric Radiative Transfer of Sunshine (for diffuse or global radiation) at any instant. Besides the atmospheric conditions, another important input is the solar geometry, which can be defined by the sun position (zenith angle and azimuth), the air mass, or by specifying the date, time and location. Optional calculations include the circumsolar irradiance, illuminance components, photosynthetically active radiation (PAR) components, and irradiance calculations in the UV, involving a variety of action spectra (such as that corresponding to the erythema). The program outputs its results to text files, which can be further imported and processed into spreadsheets. A graphic interface, providing plots of the calculated spectra