Solar Maximum Mission (2/1980-12/1989)
SMM was launched on February 14, 1980, carrying several scientific instruments to study solar flares and the active solar atmosphere. These instruments included the Ultraviolet Spectrometer and Polarimeter (UVSP), the Active Cavity Radiometer Irradiance Monitor (ACRIM), the Gamma-Ray Spectrometer (GRS), the Hard X-Ray Burst Spectrometer (HXRBS), the soft X-Ray Polychromator (XRP), the Hard X-ray Imaging Spectrometer (HXIS), and the Coronagraph Polarimeter (CP).
The ACRIM1 instrument was the first instrument to show clearly that solar irradiance does vary. The peak-to-peak TSI change was ~ 0.1 % between the activity maximum of 1980 and the minimum in 1986. This discovery provided a new paradigm for the connection between climate change and TSI variability. Correlations between TSI and climate have been made extending back in time using various solar activity proxies. The relationship between TSI and known climate changes, such as the little ice age ~(1400 - 1900), the medeival climate optimum ~(800 - 1300) and other longer term climate events are now understandable in terms of solar forcing.