PSPT Data

At HAO's Mauna Loa Solar Observatory (MLSO), the PSPT observes every day of the year for about 6-8 hours, weather permitting. The PSPT produces seeing-limited full disk digital (2048x2048) images in CaIIK (393.5+/-0.12 nm), and blue (409.4+/-0.11 nm) and red (607.1+/-0.22 nm) continuum, at an unprecedented ~0.1% photometric precision per pixel. The observing sequence is time-averaged and interlaced to produce photometric images which are averages of 30 exposures taken over approximately 5-6 minutes. Each image is processed (see below) and made available in FITS format with extensive header information.

PSPT Image Processing

• Process raw image headers and copy raw image files to the NCAR Mass Storage System (MSS). The processing of the raw image headers includes the addition of several keywords and values, re-ordering of keywords, a check of coordinate values against ephemeral values, and a check of the validity of the raw image keywords according to the FITS standard.
  
  
• Generate daily flat field images using Kuhn/Lin algorithm. See bibliography page for reference.
  
  
• Flat field regular observation images and remove linear gradient introduced by flat field.
  
  
• Uniquely determine a limb darkening fuction for "quiet sun" pixels by performing a simultaneous least-squares fit to a truncated series of Legendre polynomials in radius and Fourier sine and cosine terms in central angle. The coefficients of the limb darkening fit are then stored in the FITS header of the image, along with other relevant values used in determining the fit (i.e., sun center coordinates, solar radius, etc.).
  
  
• Perform three tests to judge the quality of each image: heliocentric north and south polar region power spectra sums and RMS of 128x128 sub-images, and determination of the limb width for the geocentric north, south, east, and west limbs. These values, along with their averages are stored in the FITS header of the image.
  
  
• Perform quality control by human inspection of each image, then store the final processed image on the NCAR Mass Storage System.