You are here

Level 1 calibration steps

The level1 data are generated by applying different calibration steps to level0 data (most of them still in beta version). Below we give an overview of the calibration procedures which are implemented at present.

All the calibration steps below leave a trace in the HISTORY keyword of the level1 FITS file. In this way it is always clear which processing steps have been performed on a particular image.

P2SW_HDRCHK: Checks critical keywords like detector temperature in the level0 header. Level0 specific keywords are removed.

P2SW_PMCDIV: Corrects the data for bad (’dead’) pixels or hypersensitive pixels. One pixel map is determined and known on the ground (pixels that are always bad), but a second set of pixels is determined actively onboard and will be given as a table of values in the FITS extension.

P2SW_PIXREP (P2SW_SATCOR): This calibration step takes care of missing pixels or pixels with unrealistic values (saturated pixels, negative valued, …). These pixel values are replaced by 3x3 median values if missing and pixels that are within 95% of their saturated value are replaced by value 4400.

P2SW_DRKSUB: Images are dark subtracted by this routine. There are two ways implemented. First, a direct subtraction of a dark FITS file, scaled for detector temperature and exposure time. Second, a subtraction of a temperature-dependent, calculated curve. More information about which technique was applied in given in the HISTORY keyword.


P2SW_FFCORR: Divide the image by the Flat Response. At present a default map is used.

P2SW_DESPIKE: This routine subtracts a 3x3 Median image from the data image, and then replaces pixels above some static threshold value with their 3x3 median value. The threshold level is given in the FITS header (HISTORY keyword).

P2SW_IMGCOR: Images are first rotated to get the Solar North up. In a second step, the pixels are slightly scaled to perfectly squared pixels. Finally, the image is centred on the solar disk centre.

P2SW_EXPNORM: Normalization to the exposure time.

The final data are given as DN/s/pixel.