The variations of solar irradiance can only be measured with a reasonable precision from space for almost all wavelengths. Yet the history of solar irradiance determinations is, with few exceptions, the history of efforts to patch the infrequent or too discontinuous space-based measurements by devising mechanisms for proxy determination of solar irradiance fluxes from ground-based obtained parameters. Although it appears that in the near future the situation will not be too different, there is

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... ome increase in the coverage of the spectral range that will be monitored. From gamma-rays to infrared light there are instruments that are now operating (e.g. GOES,Yohkoh, UARS) or are planned to operate in approved space missions (e.g. SOHO, ATLAS), or form part of proposed, not yet approved, missions. New techniques are being developed specifically for the measurement of solar irradiance variations with increased precision (e.g. cryogenic radiometer) in the next generation of space-borne measurements.