Status of the solar maximum mission



The Solar Maximum Mission (SMM) spacecraft was launched into a near-perfect 575-km orbit on February 14, 1980. All systems have been functioning normally throughout the mission. A few highlights of scientific results are: (1) The SMM obtained an extremely high-quality set of observations of the large flare that occurred on May 21. Among the most important results was the observation by the hard X ray imaging spectrometer that the brightest emission in hard X rays came from two points that are probably at the feet of a magnetic arch, coinciding closely with parts of the double-ribbon flare seen in hydrogen alpha. This observation, when combined with recent observations that flare microwave radio bursts come from the tops of the flare magnetic arches, has now created stringent observational boundary conditions for solar flare models. (2) Analyses of data from the hard X-ray burst spectrometer (Goddard Space Flight Center), combined with ground-based radio observations from Nancay, have shown that many type-IV bursts appear first in hard X rays. Subsequently, they seem to move upward through the corona at about 2000 km/s and are seen with only a short time delay as radio bursts at a height of about 0.5 solar radii. (3) The active cavity radiometer has detected definite changes in solar irradiance of about ±0.1%. No strong correlation with sunspot number is seen.