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The Solar Maximum Mission (SMM or SolarMax) was launched on February 14, 1980. It
carried several scientific instruments which provided new insights into the nature of
solar flares. The spacecraft was rescued and repaired by a 1984 Space Shuttle Challenger
mission. This rescue and repair of SMM, (153 kb GIF
image) , (124 kb GIF image) , (133 kb GIF image) , extended the useful lifetime of the
mission to allow for better coverage of the solar activity cycle. SMM reentered the
Earth's atmosphere and burned-up on December 2, 1989.
SMM carried a battery of instruments designed 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).
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Several members of the MSFC Solar Physics Group were involved with UVSP under the
direction of Dr. Einar Tandberg-Hanssen. UVSP was designed to study the ultraviolet
radiation emitted by the Sun in flares, active regions, and prominences. It was capable of
acquiring simultaneous images in four different spectral positions as it scanned across
the Sun. A rotating polarizer was used to measure magnetic fields as well.
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The ACRIM instrument package monitored the total energy output of the Sun (often
referred to as the "Solar Constant") throughout the mission with great
precision. These observation showed the expected dimming of the Sun when sunspots rotated
into view and provided important information on the extent of this dimming. More
importantly, however, ACRIM showed that the Sun is actually brighter during the maximum of
the sunspot cycle when more spots are observed on the Sun's
surface. Although the sunspots themselves are dark and
produce dimming, they are surrounded by faculae that
are bright and, on average, more than offset the dimming due to the sunspots.
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