Solar Maximum Mission Coronagraph-Polarimeter Coronal Images

The Solar Maximum Mission (SMM) Coronagraph / Polarimeter (C/P) was launched on the
SMM spacecraft on February 14, 1980. It operated in low Earth orbit from March 2, 1980 to September
23, 1980. The spacecraft attitude control system failed in November 1980, resulting in a cessation of
SMM C/P data until the spacecraft was repaired by astronauts on the Challenger space shuttle (STS-41C)
in April 1984. SMM C/P resumed data acquisition on April 26, 1984 and operated until Nov 17, 1989
when its orbit decayed and it reentered Earth’s atmosphere on December 2, 1989.

The orbital period of the SMM spacecraft was approximately 95 minutes with ~45 minutes of
occultation. SMM C/P acquired images of the solar corona from 1.8 to 4.1 solar radii over a full 360
degree field-of-view and out to 6 solar radii over the lower latitude regions. SMM C/P recorded the total
coronal brightness (F + K corona) and linear polarization using a variety of filters:

blue filter: 448.1 nm (ctr.) ; width of filter = 32.5 nm
green filter: 517.1 nm (ctr.) ; width of filter = 31.4 nm
red filter: 620.0 nm (ctr.) ; width of filter = 43.6 nm
wideband filter: 478.5 nm (ctr); width of filter = 67.3 nm
halpha emission line; 656.4 nm (ctr); width of filter = 4.2 nm
green line (FeXIV) : 530.3 nm (ctr); width of filter = 0.55 nm
green continuum: 529.7 nm (ctr); width of filter = 0.55 nm

The bulk of the data were acquired using the green filter and the halpha filter.
SMM C/P images are 448 x 448 pixels with a pixel size is 6.4 arcsec with a spatial resolution of ~12
arcsec. Coronal images were acquired in sectors around the Sun (north, east, south, west, ne, nw, se,
sw) so that 4 sector images were needed to construct a full 360 degree view of the corona. Images were
acquired every ~90 seconds until late 1986 when a tape recorder failure resulted in a temporal
resolution of 8 minutes.

Images are available in FITS format and are fully calibrated intensity in units of 1.e-11 B/Bsun, where
Bsun is the brightness of the solar disk. The stray light radiance noise level is ~5.e-10 B/Bsun. Data are
also available with vignetting in the images to provide higher contrast for tracking coronal structures
such as CMEs, however, these images should not be used to compute calibrated brightness, density or
mass.