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CaIIK - Photoheliograms

2k x 2k CCD Full Disk Heliograms at 393.37 nm (0.3 nm FWHM)

» go direct to the CaIIK synoptic data archives directory...
» Instrument Operations Timeline
» CaIIK - Instrument and Data Processing Procedures Description...

Data Description - Contents

» Observing Programme
» Coordinate System and Image Orientation
» Data Levels
» Data Formats and File Names
» Daily Synoptic Data Archives Directory Structure"

Observing Programme

A. Patrol of the solar chromosphere. Obtain a continuous time series of full disk CaII K images whenever weather conditions permit. Instrumental cadence standard is 10 images/min. The cadence in the long term archives may be reduced to 3 image/min on periods with low or no visible solar activity by selecting the "best image" of that time interval.
B. Publish a representative daily synoptic image of the solar photosphere out of the time series.

Coordinate System and Image Orientation

Coordinate System
Basically the images are mapped as the solar disk would be seen in the sky with the eye, i. e. N is up, E is to the left.
Coordinate Origin
The first pixel in the data array is the left bottom edge of the image.
Heliographic Coordinates
P is the position angle of the solar rotation axis (solar N), reckoned positive from (celestial) N towards E.

Data Levels

A. Raw Level Data as written by the image acquisition software. Basically all data are in FITS, specific keywords denote properties which have to be recorded at observation time and cannot be restored or recalculated at a later time. A dark current frames (DC) is recorded each day.
B. Archive Level Basically raw data, i. e. the image itself or the pixel data remain unchanged but prepared for archiving and better usability. The processing comprises a quality check of the individual images and a cadence reduction. We avoid any rebinning, averaging or other pixel value manipulation except a) a shifting of the solar disk towards the center coordinates of the field of view (pixel array) by shifting an integer number of pixels and b) setting pixels far outside the solar disk to 0 for a better compression of the data. More keywords are inserted into the FITS headers to make the data compliant with common accepted data standards.
C. Synoptic Level A gain table correction (flatfield) which assumes circular symmetry on large scales on the solar disk ("Burlov"-method) is applied to archive level data. This method delivers also a center to limb variation (CLV) profile and therefore a "quiet Sun map". Dividing the flatfielded image by this "quiet Sun map" yields a normalized ("flat") solar disk image where the quiet sun level corresponds to 1 in the data array. In particular for the JPEG copies the contrast is enhanced by unsharp masking and a linear rescaling of the actual intensity range (e.g. 0...120% of the int. at disk center) to full byte scale (0...255), for individual properties of the data products see the formats and the data processing pipeline section.
The daily synoptic image is processed according to this level and published in various formats.

Data Formats and File Names

File Explanation
A. Raw Level Data 
caYYYYMMDD_hhmmss.fts.gz
 raw level image frame, 2 Byte integer, compressed FITS 
dcYYYYMMDD_hhmmss.fts.gz
 raw level dark current frame, 2 Byte integer, compressed FITS
B. Archive Level Data 
kanz_caiik_YYYYMMDD_hhmmss.fts.gz
 archive level image frame, 2 Byte integer, compressed FITS 
kanz_caiik_YYYYMMDD_hhmmss.jpg
 archive level image frame, half scale, JPEG
C. Synoptic Level Data 
kanz_caiik_fi_YYYYMMDD_hhmmss.fts.gz
 archive level representation of the daily synoptic image, 2 Byte integer, compressed FITS 
kanz_caiik_fq_YYYYMMDD_hhmmss.fts.gz
 center to limb variation (CLV) profile, derived by the flatfielding procedure, compressed FITS ASCII table 
kanz_caiik_fc_YYYYMMDD_hhmmss.fts.gz
 normalized image (CLV contrast compensated), rescaled to by use of BSCALE=0.01 to 1 Byte integer, compressed FITS 
kanz_caiik_fc_YYYYMMDD_hhmmss.jpg
 normalized image (CLV contrast compensated), unsharp masking, intensity rescaling 40...120% -> 0...255, derotated for P and angle Θ, heliograph. coordinate grid, half scale, JPEG 
kanz_caiik_fd_YYYYMMDD_hhmmss.fts.gz
 gain table corrected image, 2 Byte integer, compressed FITS 
kanz_caiik_fd_YYYYMMDD_hhmmss.jpg
 gain table corrected image, unsharp masking, intensity rescaling 0...120% -> 0...255, derotated for P and angle Θ, half scale, JPEG 
kanz_caiik_ff_YYYYMMDD.fts.gz
 Flat field according to Kuhn-Lin-Loranz method, 4 Byte float, normed to 1, compressed FITS 
kanz_caiik_fm_YYYYMMDD.fts.gz
 Flat field according to Kuhn-Lin-Loranz method smoothed, 4 Byte float, normed to 1, compressed FITS 
kanz_caiik_fp_YYYYMMDD.fts.gz
 profile of flat field according to Kuhn-Lin-Loranz method, smoothed, 4 Byte float, normed to 1, compressed FITS
YYYYMMDD_hhmmss...date and time of the observation
The file names comply with the SOHO file name convention for synoptic data

Daily Synoptic Data Archives Directory Structure (rel. to web-root)

»go to the CaIIK synoptic data archives directory...
Directory Explanation 
http://cesar.kso.ac.at/caiis/...
 ...CaIIK synoptic root 
http://cesar.kso.ac.at/caiis/FITS/YYYY
 ...FITS format subdirectory 
http://cesar.kso.ac.at/caiis/FITS/arch/YYYY
 ...synoptic images, archive level format 
http://cesar.kso.ac.at/caiis/FITS/clv/YYYY
 ...CLV tables 
http://cesar.kso.ac.at/caiis/FITS/normal/YYYY
 ...synoptic level, normalized image (high contrast) 
http://cesar.kso.ac.at/caiis/FITS/synoptic/YYYY
 ...synoptic level, low (normal) contrast 
http://cesar.kso.ac.at/caiis/FITS/flat/YYYYMMDD
 ...flat field data - Kuhn-Lin-Loranz 
http://cesar.kso.ac.at/caiis/JPEG/...
 ...JPEG format subdirectory 
http://cesar.kso.ac.at/caiis/JPEG/normal/YYYY
 ...synoptic level, high contrast 
http://cesar.kso.ac.at/caiis/JPEG/synoptic/YYYY
 ...synoptic level, low (normal) contrast 
http://cesar.kso.ac.at/caiis/JPEG/recent/YYYY
 ...recent (last week) synoptic level, low and high contrast

YYYY... subdirectory according to the year of observation

 

  
 
 
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